Herb & supplement monograph

Green Tea Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by ·Updated July 2026
What is this page for?

First and foremost: how Green Tea interacts with medications. The heart of this page is the interaction list — every drug Green Tea is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Green Tea is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Green Tea Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Green Tea drug interaction is low for most people, but a handful of specific medicines are affected in well-documented ways. Only a small fraction of the listed interactions are rated major, and most of the rest rest on theoretical or animal findings tied to green tea's caffeine content.

Interactions deserving the most attention

The best-supported concerns involve green tea lowering the levels of certain medicines. Human studies show it can sharply reduce nadolol, a blood pressure medicine, and modestly lower atorvastatin, a cholesterol drug, potentially making either less effective. Combining green tea's caffeine with ephedrine may raise the risk of serious stimulant effects such as dangerously high blood pressure. Smaller human studies also show reduced levels of celiprolol and the allergy medicine fexofenadine.

What the rest of the list means

Most of the long list traces back to caffeine, which many drugs slow the body's clearance of, or to possible effects on transporters that move medicines into the body. Many of these predictions come from lab or animal research and have not been shown to cause meaningful changes in people. For example, moderate green tea drinking is unlikely to significantly raise bleeding risk with blood thinners.

Check your medications against Green Tea

Based on HelloPharmacist’s Green Tea interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Green Tea

1293 medications have a known interaction with Green Tea, graded by severity. Select any drug for the full evidence-based detail.

13 major interactions. These combinations can be clinically significant — best avoided, or used only with close professional supervision. Always check with your pharmacist before combining them with Green Tea.

2,830 drugs
Aminophylline, Amobarbital, EphedrineAmesec
Major Ephedrine

Theoretically, concomitant use might increase the risk for stimulant adverse effects.

Read the full Green Tea + Aminophylline, Amobarbital, Ephedrine interaction
AtorvastatinAtorvaliq
Major Atorvastatin (lipitor)

Green tea extract seems to reduce the levels and clinical effects of atorvastatin.

Read the full Green Tea + Atorvastatin interaction Atorvastatin drug page: uses, dosage & side effects
Atorvastatin CalciumLipitor
Major Atorvastatin (lipitor)

Green tea extract seems to reduce the levels and clinical effects of atorvastatin.

Read the full Green Tea + Atorvastatin Calcium interaction Atorvastatin Calcium drug page: uses, dosage & side effects
Bendroflumethiazide, NadololCorzide
Major Nadolol (corgard)

Green tea seems to reduce the levels and clinical effects of nadolol.

Read the full Green Tea + Bendroflumethiazide, Nadolol interaction
Carbetapentane Tannate, Chlorpheniramine Tannate, Ephedrine Tannate, Phenylephrine TannateQuadratuss, Ry Tuss, Rynatuss, Tri Tannate Plus
Major Ephedrine

Theoretically, concomitant use might increase the risk for stimulant adverse effects.

Read the full Green Tea + Carbetapentane Tannate, Chlorpheniramine Tannate, Ephedrine Tannate, Phenylephrine Tannate interaction
Dyphylline, Ephedrine, Guaifenesin, PhenobarbitalLufyllin-EPG
Major Ephedrine

Theoretically, concomitant use might increase the risk for stimulant adverse effects.

Read the full Green Tea + Dyphylline, Ephedrine, Guaifenesin, Phenobarbital interaction
Ephedrine, Guaifenesin (otc Drug)Ephedrine Formula 400, Ephedrine Plus Tabs
Major Ephedrine

Theoretically, concomitant use might increase the risk for stimulant adverse effects.

Read the full Green Tea + Ephedrine, Guaifenesin (otc Drug) interaction
Ephedrine, Guaifenesin, Phenobarbital, TheophyllineMudrane GG
Major Ephedrine

Theoretically, concomitant use might increase the risk for stimulant adverse effects.

Read the full Green Tea + Ephedrine, Guaifenesin, Phenobarbital, Theophylline interaction
Ephedrine, Hydroxyzine, TheophyllineAmi Rax, Marax
Major Ephedrine

Theoretically, concomitant use might increase the risk for stimulant adverse effects.

Read the full Green Tea + Ephedrine, Hydroxyzine, Theophylline interaction
Ephedrine, Phenobarbital, Potassium Iodide, TheophyllineMudrane, Quadrinal
Major Ephedrine

Theoretically, concomitant use might increase the risk for stimulant adverse effects.

Read the full Green Tea + Ephedrine, Phenobarbital, Potassium Iodide, Theophylline interaction
Ephedrine, Phenobarbital, TheophyllineTedral
Major Ephedrine

Theoretically, concomitant use might increase the risk for stimulant adverse effects.

Read the full Green Tea + Ephedrine, Phenobarbital, Theophylline interaction
Ezetimibe, AtorvastatinLiptruzet
Major Atorvastatin (lipitor)

Green tea extract seems to reduce the levels and clinical effects of atorvastatin.

Read the full Green Tea + Ezetimibe, Atorvastatin interaction
NadololCorgard, Nadolol
Major Nadolol (corgard)

Green tea seems to reduce the levels and clinical effects of nadolol.

Read the full Green Tea + Nadolol interaction Nadolol drug page: uses, dosage & side effects
6-mercaptopurinePurinethol
Moderate Hepatotoxic Drugs

Theoretically, concomitant use might have additive adverse hepatotoxic effects.

Read the full Green Tea + 6-mercaptopurine interaction 6-mercaptopurine drug page: uses, dosage & side effects
Abacavir Sulfate, Dolutegravir, LamivudineTriumeq
Moderate Hepatotoxic Drugs

Theoretically, concomitant use might have additive adverse hepatotoxic effects.

Read the full Green Tea + Abacavir Sulfate, Dolutegravir, Lamivudine interaction Abacavir Sulfate, Dolutegravir, Lamivudine drug page: uses, dosage & side effects
Abacavir, LamivudineEpzicom
Moderate Hepatotoxic Drugs

Theoretically, concomitant use might have additive adverse hepatotoxic effects.

Read the full Green Tea + Abacavir, Lamivudine interaction
AbametapirXeglyze
Moderate Cytochrome P450 1a2 (cyp1a2) Inhibitors

Theoretically, concomitant use might increase the levels and adverse effects of caffeine.

Read the full Green Tea + Abametapir interaction
AbciximabReoPro
Moderate Anticoagulant/antiplatelet Drugs

Theoretically, green tea may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.

Read the full Green Tea + Abciximab interaction
Abiraterone
Moderate Cytochrome P450 1a2 (cyp1a2) Inhibitors

Theoretically, concomitant use might increase the levels and adverse effects of caffeine.

Read the full Green Tea + Abiraterone interaction Abiraterone drug page: uses, dosage & side effects
Abiraterone AcetateYonsa, Zytiga
Moderate Hepatotoxic Drugs

Theoretically, concomitant use might have additive adverse hepatotoxic effects.

Read the full Green Tea + Abiraterone Acetate interaction Abiraterone Acetate drug page: uses, dosage & side effects
AbrocitinibCibinqo
Moderate Anticoagulant/antiplatelet Drugs

Theoretically, green tea may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.

Read the full Green Tea + Abrocitinib interaction Abrocitinib drug page: uses, dosage & side effects
AcalabrutinibCalquence
Moderate P-glycoprotein Substrates

Green tea might increase the levels and adverse effects of P-glycoprotein (P-gp) substrates.

Read the full Green Tea + Acalabrutinib interaction Acalabrutinib drug page: uses, dosage & side effects
AcarboseGlucobay, Prandase, Precose
Moderate Hepatotoxic Drugs

Theoretically, concomitant use might have additive adverse hepatotoxic effects.

Read the full Green Tea + Acarbose interaction Acarbose drug page: uses, dosage & side effects
AcebutololRhotral, Sectral
Moderate Hepatotoxic Drugs

Theoretically, concomitant use might have additive adverse hepatotoxic effects.

Read the full Green Tea + Acebutolol interaction Acebutolol drug page: uses, dosage & side effects
AcenocoumarolSintrom
Moderate Anticoagulant/antiplatelet Drugs

Theoretically, green tea may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.

Read the full Green Tea + Acenocoumarol interaction
AcetaminophenChildren's Tylenol, Children's Tylenol Meltaways, Tylenol, Tylenol Ex Strength
Moderate Hepatotoxic Drugs

Theoretically, concomitant use might have additive adverse hepatotoxic effects.

Read the full Green Tea + Acetaminophen interaction Acetaminophen drug page: uses, dosage & side effects
Acetaminophen, AspirinGemnisyn
Moderate Hepatotoxic Drugs

Theoretically, concomitant use might have additive adverse hepatotoxic effects.

Read the full Green Tea + Acetaminophen, Aspirin interaction
Acetaminophen, Aspirin, CaffeineExcedrin, Excedrin Extra Strength, Excedrin Migraine
Moderate Anticoagulant/antiplatelet Drugs

Theoretically, green tea may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.

Read the full Green Tea + Acetaminophen, Aspirin, Caffeine interaction
Acetaminophen, Brompheniramine, PhenylpropanolamineDimetapp Cold and Flu
Moderate Stimulant Drugs

Theoretically, concomitant use might increase stimulant adverse effects.

Read the full Green Tea + Acetaminophen, Brompheniramine, Phenylpropanolamine interaction
Acetaminophen, ButalbitalAxocet, Bancap, Bucet, Butex Forte, Esgic CF, Orbivan CF +5 more
Moderate Hepatotoxic Drugs

Theoretically, concomitant use might have additive adverse hepatotoxic effects.

Read the full Green Tea + Acetaminophen, Butalbital interaction
Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

  • Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
  • Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
  • Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
  • No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

  • Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
  • Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
  • Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

  • Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
  • Each drug listed above links to the full report for that exact Green Tea combination — clinical detail, likelihood, evidence level, and citations.
  • Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.
The big picture

The kinds of drugs Green Tea affects

Every type of medication (drug category) Green Tea is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 58 drug categories Green Tea interacts with
Atorvastatin (lipitor)EphedrineNadolol (corgard)5-fluorouracilAdenosine (adenocard)Anticoagulant/antiplatelet DrugsBeta-adrenergic AgonistsBortezomib (velcade)Carbamazepine (tegretol)Celiprolol (celicard)Cimetidine (tagamet)Clozapine (clozaril)Contraceptive DrugsCytochrome P450 1a2 (cyp1a2) InhibitorsDipyridamole (persantine)Disulfiram (antabuse)Diuretic DrugsEstrogensEthosuximide (zarontin)Felbamate (felbatol)Fexofenadine (allegra)Flutamide (eulexin)Fluvoxamine (luvox)Hepatotoxic DrugsImatinib (gleevec)LisinoprilLithiumMonoamine Oxidase Inhibitors (maois)NicotineNintedanib (ofev)Organic Anion-transporting Polypeptide Substrates (oatp)P-glycoprotein SubstratesPentobarbital (nembutal)Phenobarbital (luminal)PhenylpropanolaminePhenytoin (dilantin)Pioglitazone (actos)Quinolone AntibioticsRiluzole (rilutek)Rosuvastatin (crestor)Stimulant DrugsTheophyllineValproateVerapamil (calan, Others)Warfarin (coumadin)Alcohol (ethanol)Antidiabetes DrugsCytochrome P450 3a4 (cyp3a4) SubstratesFluconazole (diflucan)Metformin (glucophage)Methoxsalen (oxsoralen)Mexiletine (mexitil)Midazolam (versed)Nicardipine (cardene)PhenothiazinesTerbinafine (lamisil)Tiagabine (gabitril)Ticlopidine (ticlid)
Atorvastatin (Lipitor)

Green tea extract seems to reduce the levels and clinical effects of atorvastatin.
In healthy humans, taking green tea extract 300 mg or 600 mg along with atorvastatin reduces plasma levels of atorvastatin by approximately 24%. The elimination of atorvastatin is not affected. Atorvastatin is a substrate of organic anion-transporting polypeptides (OATPs). Research shows that two of the major catechins found in green tea, epicatechin gallate (ECG) and epigallocatechin gallate (EGCG), inhibit OATPs. Some OATPs are expressed in the small intestine and are responsible for the uptake of drugs and other compounds, which may have resulted in reduced plasma levels of atorvastatin. It is not clear if drinking green tea alters the absorption of atorvastatin.

Likelihood Likely Evidence B
Ephedrine

Theoretically, concomitant use might increase the risk for stimulant adverse effects.
Green tea contains caffeine. There is evidence that using ephedrine with caffeine might increase the risk of serious life-threatening or debilitating adverse effects such as hypertension, myocardial infarction, stroke, seizures, and death.

Likelihood Probable Evidence D
Nadolol (Corgard)

Green tea seems to reduce the levels and clinical effects of nadolol.
Preliminary clinical research shows that green tea consumption reduces plasma concentrations of nadolol. Compared to a control group, both peak levels and total drug exposure (AUC) of nadolol were reduced by approximately 85% in subjects who drank green tea daily for two weeks. Drinking green tea with nadolol also significantly reduced nadolol's systolic blood pressure lowering effect. Other clinical research shows that a single dose of green tea can affect plasma nadolol levels for at least one hour. Green tea catechins have been shown to inhibit organic anion transporting polypeptides (OATP), one of which, OATP1A2, is involved in the uptake of nadolol in the intestine The interaction is thought to be due primarily to the epigallocatechin gallate (EGCG) content of green tea.

Likelihood Likely Evidence B
5-Fluorouracil

Theoretically, high doses of green tea might increase the effects and side effects of 5-fluorouracil.
Animal research shows that taking green tea in amounts equivalent to about 6 cups daily in humans for 4 weeks prior to receiving a single injection of 5-fluorouracil increases the maximum plasma levels of 5-fluorouracil by about 2.5-fold and the area under the curve by 425%.

Likelihood Possible Evidence D
Adenosine (Adenocard)

Theoretically, green tea might decrease the vasodilatory effects of adenosine and interfere with its use prior to stress testing.
Green tea contains caffeine. Caffeine is a competitive inhibitor of adenosine at the cellular level. However, caffeine doesn't seem to affect supplemental adenosine because high interstitial levels of adenosine overcome the antagonistic effects of caffeine. It is recommended that methylxanthines and methylxanthine-containing products be stopped 24 hours prior to pharmacological stress tests. However, methylxanthines appear more likely to interfere with dipyridamole (Persantine) than adenosine-induced stress testing.

Likelihood Possible Evidence B
Anticoagulant/Antiplatelet Drugs

Theoretically, green tea may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Conflicting reports exist regarding the effect of green tea on bleeding risk when used with anticoagulant or antiplatelet drugs; however, most evidence suggests that drinking green tea in moderate amounts is unlikely to cause a significant interaction. Green tea contains small amounts of vitamin K, approximately 7 mcg per cup. Some case reports have associated the antagonism of warfarin with the vitamin K content of green tea. However, these reports are rare, and very large doses of green tea (about 8-16 cups daily) appear to be needed to cause these effects. Furthermore, the catechins and caffeine in green tea are reported to have antiplatelet activity.

Likelihood Unlikely Evidence D
Beta-Adrenergic Agonists

Green tea contains caffeine. Theoretically, concomitant use of large amounts of caffeine might increase cardiac inotropic effects of beta-agonists.

Likelihood Probable Evidence D
Bortezomib (Velcade)

Theoretically, green tea might interfere with the effects of bortezomib.
In vitro research shows that green tea polyphenols, such as epigallocatechin gallate (EGCG), interact with bortezomib and block its proteasome inhibitory action. This prevents the induction of cell death in multiple myeloma or glioblastoma cancer cell lines. Advise patients taking bortezomib, not to take green tea.

Likelihood Possible Evidence D
Carbamazepine (Tegretol)

Theoretically, green tea might reduce the effects of carbamazepine and increase the risk for convulsions.
Green tea contains caffeine. Animal research suggests that taking caffeine can lower the anticonvulsant effects of carbamazepine and can induce seizures when taken in doses above 400 mg/kg. Human research has shown that taking caffeine 300 mg in three divided doses along with carbamazepine 200 mg reduces the bioavailability of carbamazepine by 32% and prolongs the plasma half-life of carbamazepine 2-fold in healthy individuals.

Likelihood Possible Evidence D
Celiprolol (Celicard)

Theoretically, green tea might reduce the levels and clinical effects of celiprolol.
In a small human study, taking green tea daily for 4 days appears to decrease blood and urine levels of celiprolol by at least 98%. This interaction is possibly due to the inhibition of organic anion transporting polypeptide (OATP). Green tea catechins have been shown to inhibit organic anion transporting polypeptides (OATP), one of which, OATP1A2, is found in the intestine The interaction is thought to be due primarily to the epigallocatechin gallate (EGCG) content of green tea.

Likelihood Possible Evidence D
Cimetidine (Tagamet)

Theoretically, concomitant use might increase the effects and adverse effects of caffeine in green tea.
Green tea contains caffeine. Cimetidine can reduce caffeine clearance by 31% to 42%.

Likelihood Likely Evidence B
Clozapine (Clozaril)

Theoretically, green tea might increase the levels and adverse effects of clozapine and acutely exacerbate psychotic symptoms.
Animal research suggests that, although green tea extract does not affect the elimination of clozapine, it delays the time to reach peak concentration and reduces the peak plasma levels. Also, concomitant administration of green tea and clozapine might theoretically cause acute exacerbation of psychotic symptoms due to the caffeine in green tea. Caffeine can increase the effects and toxicity of clozapine. Caffeine doses of 400-1000 mg daily inhibit clozapine metabolism. Clozapine is metabolized by cytochrome P450 1A2 (CYP1A2). Researchers speculate that caffeine might inhibit CYP1A2. However, there is no reliable evidence that caffeine affects CYP1A2. There is also speculation that genetic factors might make some patients be more sensitive to the interaction between clozapine and caffeine.

Likelihood Possible Evidence B
Contraceptive Drugs

Theoretically, concomitant use might increase the effects and adverse effects of caffeine found in green tea.
Green tea contains caffeine. Oral contraceptives can decrease caffeine clearance by 40% to 65%.

Likelihood Probable Evidence B
Cytochrome P450 1A2 (Cyp1A2) Inhibitors

Theoretically, concomitant use might increase the levels and adverse effects of caffeine.
Green tea contains caffeine. Caffeine is metabolized by cytochrome P450 1A2 (CYP1A2),. Theoretically, drugs that inhibit CYP1A2 may decrease the clearance rate of caffeine from green tea and increase caffeine levels.

Likelihood Possible Evidence D
Dipyridamole (Persantine)

Theoretically, green tea might decrease the vasodilatory effects of dipyridamole and interfere with its use prior to stress testing.
Green tea contains caffeine. Caffeine might inhibit dipyridamole-induced vasodilation. It is recommended that methylxanthines and methylxanthine-containing products be stopped 24 hours prior to pharmacological stress tests. Methylxanthines appear more likely to interfere with dipyridamole (Persantine) than adenosine-induced stress testing.

Likelihood Probable Evidence B
Disulfiram (Antabuse)

Theoretically, disulfiram might increase the risk of adverse effects from caffeine.
In human research, disulfiram decreases the clearance and increases the half-life of caffeine.

Likelihood Probable Evidence B
Diuretic Drugs

Theoretically, using green tea with diuretic drugs might increase the risk of hypokalemia.
Green tea contains caffeine. In excessive amounts, caffeine can reduce potassium levels due to stimulation of the sodium-potassium pump. Diuretics can also cause lower potassium levels.

Likelihood Possible Evidence D
Estrogens

Theoretically, estrogens might increase the levels and adverse effects of caffeine.
Green tea contains caffeine. Estrogen inhibits caffeine metabolism.

Likelihood Probable Evidence B
Ethosuximide (Zarontin)

Theoretically, green tea might reduce the effects of ethosuximide and increase the risk for convulsions.
Green tea contains caffeine. Animal research suggests that caffeine 92.4 mg/kg can decrease the anticonvulsant activity of ethosuximide. However, this effect has not been reported in humans.

Likelihood Possible Evidence D
Felbamate (Felbatol)

Theoretically, green tea might reduce the effects of felbamate and increase the risk for convulsions.
Green tea contains caffeine. Animal research suggests that a high dose of caffeine 161.7 mg/kg can decreases the anticonvulsant activity of felbamate. However, this effect has not been reported in humans.

Likelihood Possible Evidence D
Fexofenadine (Allegra)

Green tea can decrease blood levels of fexofenadine.
Clinical research shows that green tea can significantly decrease blood levels and excretion of fexofenadine. Taking green tea extract with a dose of fexofenadine decreased bioavailability of fexofenadine by about 30%. In vitro, green tea inhibits the cellular accumulation of fexofenadine by inhibiting the organic anion transporting polypeptide (OATP) drug transporter. Research shows that two of the major catechins found in green tea, epicatechin gallate (ECG) and epigallocatechin gallate (EGCG), inhibit OATPs, specifically OATP1A2, OATP1B1, and OATP2B1. In addition, green tea has been shown to reduce the absorption of some drugs that are OATP substrates.

Likelihood Probable Evidence B
Flutamide (Eulexin)

Theoretically, green tea might increase the levels and adverse effects of flutamide.
Green tea contains caffeine. In vitro evidence suggests that caffeine can inhibit the metabolism of flutamide. Theoretically, concomitant use of caffeine and flutamide might increase serum concentrations of flutamide and increase the risk adverse effects.

Likelihood Possible Evidence D
Fluvoxamine (Luvox)

Theoretically, fluvoxamine might increase the levels and adverse effects of caffeine.
Green tea contains caffeine. Fluvoxamine reduces caffeine metabolism.

Likelihood Probable Evidence D
Hepatotoxic Drugs

Theoretically, concomitant use might have additive adverse hepatotoxic effects.
Green tea extract supplements have been linked to several cases of hepatotoxicity and might have additive hepatotoxic effects with other drugs..

Likelihood Unlikely Evidence D
Imatinib (Gleevec)

Theoretically, green tea might reduce the levels and clinical effects of imatinib.
In animal research, a single dose of green tea extract reduces the area under the curve (AUC) of imatinib by up to approximately 64% and its main metabolite N-desmethyl imatinib by up to approximately 81%. This interaction has not been shown in humans. The mechanism of action is unclear but may involve multiple pathways.

Likelihood Possible Evidence D
Lisinopril

Theoretically, green tea might reduce the levels and clinical effects of lisinopril.
Preliminary clinical research shows that a single dose of green tea extract reduces plasma concentrations of lisinopril. Compared to a control group, peak levels and area under the curve (AUC) of lisinopril were reduced by approximately 71% and 66%, respectively. This may be due to inhibition of organic anion transporting polypeptides (OATP) by green tea catechins The interaction is thought to be due primarily to the epigallocatechin gallate (EGCG) content of green tea.

Likelihood Probable Evidence B
Lithium

Theoretically, abrupt green tea withdrawal might increase the levels and adverse effects of lithium.
Green tea contains caffeine. Abrupt caffeine withdrawal can increase serum lithium levels. Two cases of lithium tremor that worsened with abrupt coffee withdrawal have been reported.

Likelihood Probable Evidence D
Monoamine Oxidase Inhibitors (Maois)

Theoretically, concomitant use might increase the risk of a hypertensive crisis.
Green tea contains caffeine. Caffeine has been shown to inhibit monoamine oxidase (MAO) A and B in laboratory studies. Concomitant intake of large amounts of caffeine with MAOIs might precipitate a hypertensive crisis. In a case report, a patient that consumed 10-12 cups of caffeinated coffee and took the MAOI tranylcypromine presented with severe hypertension. Hypertension was resolved after the patient switched to drinking decaffeinated coffee.

Likelihood Possible Evidence D
Nicotine

Theoretically, concomitant use might increase the risk of hypertension.
Green tea contains caffeine. Concomitant use of caffeine and nicotine has been shown to have additive cardiovascular effects, including increased heart rate and blood pressure. Blood pressure was increased by 10.8/12.4 mmHg when the agents were used concomitantly.

Likelihood Probable Evidence D
Nintedanib (Ofev)

Green tea seems to reduce the levels of nintedanib.
Clinical research shows that green tea can significantly decrease blood levels of nintedanib. Taking green tea extract twice daily for 7 days 30 minutes prior to a meal along with nintedanib with the meal decreased the 12-hour area under the curve (AUC) values for nintedanib by 21%. There was no effect on the maximum concentration of nintedanib.

Likelihood Probable Evidence B
Organic Anion-Transporting Polypeptide Substrates (Oatp)

Theoretically, green tea might reduce the absorption of organic anion-transporting polypeptide (OATP) substrates.
OATPs are expressed in the small intestine and liver and are responsible for the uptake of drugs and other compounds. Research shows that two of the major catechins found in green tea, epicatechin gallate (ECG) and epigallocatechin gallate (EGCG), inhibit OATPs, specifically OATP1A2, OATP1B1, and OATP2B1. In addition, green tea has been shown to reduce the absorption of some drugs that are OATP substrates, including lisinopril, and celiprolol.

Likelihood Probable Evidence D
P-Glycoprotein Substrates

Green tea might increase the levels and adverse effects of P-glycoprotein (P-gp) substrates.
In vitro research and case reports suggest that green tea inhibits drug efflux by P-gp, potentially increasing serum levels of P-gp substrates. Case reports from the World Health Organization (WHO) adverse drug reaction database describe increased toxicity in patients taking green tea and certain P-gp substrates.

Likelihood Possible Evidence D
Pentobarbital (Nembutal)

Theoretically, green tea might decrease the effects of pentobarbital.
Green tea contains caffeine. Theoretically, caffeine might negate the hypnotic effects of pentobarbital.

Likelihood Possible Evidence B
Phenobarbital (Luminal)

Theoretically, green tea might reduce the effects of phenobarbital and increase the risk for convulsions.
Green tea contains caffeine. Animal research suggests that caffeine can decrease the anticonvulsant activity of phenobarbital. The exact mechanism of this interaction is unclear.

Likelihood Possible Evidence D
Phenylpropanolamine

Theoretically, phenylpropanolamine might increase the risk of hypertension, as well as the levels and adverse effects of caffeine.
Green tea contains caffeine. Concomitant use of phenylpropanolamine and caffeine might cause an additive increase in blood pressure. Phenylpropanolamine also seems to increase caffeine serum levels.

Likelihood Probable Evidence B
Phenytoin (Dilantin)

Theoretically, green tea might reduce the effects of phenytoin and increase the risk for convulsions.
Green tea contains caffeine. Animal research suggests that caffeine can decrease the anticonvulsant activity of phenytoin. The effect does not seem to be related to the seizure threshold-lowering effects of caffeine. However, the exact mechanism of this interaction is unclear.

Likelihood Possible Evidence D
Pioglitazone (Actos)

Theoretically, green tea might increase the levels and clinical effects of pioglitazone.
Green tea contains caffeine. Animal research suggests that caffeine can modestly increase the maximum concentration, area under the curve, and half-life of pioglitazone, and also reduce its clearance. This increased the antidiabetic effects of pioglitazone. However, the exact mechanism of this interaction is unclear.

Likelihood Possible Evidence D
Quinolone Antibiotics

Theoretically, quinolone antibiotics might increase the levels and adverse effects of caffeine.
Green tea contains caffeine. Quinolones (also called fluoroquinolones) can decrease caffeine clearance by inhibiting cytochrome P450 1A2 (CYP1A2) enzyme.

Likelihood Probable Evidence B
Riluzole (Rilutek)

Theoretically, concomitant use might increase the levels and adverse effects of both caffeine and riluzole.
Green tea contains caffeine. Caffeine and riluzole are both metabolized by cytochrome P450 1A2, and concomitant use might reduce metabolism of one or both agents.

Likelihood Possible Evidence D
Rosuvastatin (Crestor)

Theoretically, green tea extract might alter the absorption and distribution of rosuvastatin.
In animal research, giving green tea extract with rosuvastatin increased plasma levels of rosuvastatin. Rosuvastatin is a substrate of organic anion-transporting polypeptide (OATP)1B1, which is expressed in the liver. The increased plasma levels may have been related to inhibition of OATP1B1. However, in humans, taking EGCG with rosuvastatin reduced plasma levels of rosuvastatin, suggesting an inhibition of intestinal OATP. It is not clear if drinking green tea alters the absorption of rosuvastatin.

Likelihood Possible Evidence D
Stimulant Drugs

Theoretically, concomitant use might increase stimulant adverse effects.
Green tea contains caffeine. Due to the central nervous system (CNS) stimulant effects of caffeine, concomitant use with stimulant drugs can increase the risk of adverse effects.

Likelihood Probable Evidence C
Theophylline

Theoretically, green tea might increase the levels and adverse effects of theophylline.
Green tea contains caffeine. Large amounts of caffeine might inhibit theophylline metabolism.

Likelihood Probable Evidence B
Valproate

Theoretically, green tea might reduce the effects of valproate and increase the risk for convulsions.
Green tea contains caffeine. Animal research suggests that caffeine can decrease the anticonvulsant activity of valproate. However, the exact mechanism of this interaction is unclear.

Likelihood Possible Evidence D
Verapamil (Calan, Others)

Theoretically, concomitant use might increase the levels and adverse effects of both verapamil and caffeine.
Animal research suggests that the green tea constituent EGCG increases the area under the curve (AUC) values for verapamil by up to 111% and its metabolite norverapamil by up to 87%, likely by inhibiting P-glycoprotein. Also, theoretically, concomitant use of verapamil and caffeinated beverages such as green tea might increase plasma caffeine concentrations and the risk of adverse effects, due to the caffeine contained in green tea. Verapamil increases plasma caffeine concentrations by 25%.

Likelihood Possible Evidence D
Warfarin (Coumadin)

Theoretically, green tea may increase the risk of bleeding if used with warfarin.
Conflicting reports exist regarding the potential of green tea to antagonize the effect of warfarin; however, most evidence suggests that drinking green tea in moderation is unlikely to cause a significant interaction. Green tea contains a small amount of vitamin K, approximately 7 mcg per cup. Some case reports have associated the antagonism of warfarin with the vitamin K content of green tea. However, these reports are rare, and very large doses of green tea (about 8-16 cups daily) appear to be needed to cause these effects. Therefore, use of green tea in moderate amounts is unlikely to antagonize the effects of warfarin; however, very large doses should be avoided.

Likelihood Unlikely Evidence D
Alcohol (Ethanol)

Theoretically, alcohol might increase the levels and adverse effects of caffeine.
Green tea contains caffeine. Concomitant use of alcohol and caffeine can increase caffeine serum concentrations and the risk of caffeine adverse effects. Alcohol reduces caffeine metabolism.

Likelihood Possible Evidence D
Antidiabetes Drugs

Theoretically, taking green tea with antidiabetes drugs might interfere with blood glucose control.
Concomitant use of green tea and antidiabetes drugs might interfere with blood glucose control. The data are conflicting. Reports claim that green tea and/or caffeine, a constituent of green tea, might increase or decrease blood sugar.

Likelihood Unlikely Evidence B
Cytochrome P450 3A4 (Cyp3A4) Substrates

Green tea is unlikely to produce clinically significant changes in the levels and clinical effects of CYP3A4 substrates.
In vitro and in vivo research suggests that green tea can inhibit intestinal CYP3A and induce hepatic CYP3A4 enzymes. However, this effect is unlikely to be clinically significant, as green tea does not appear to affect CYP3A4 activity in humans.

Likelihood Unlikely Evidence D
Fluconazole (Diflucan)

Theoretically, fluconazole might increase the levels and adverse effects of caffeine.
Green tea contains caffeine. Fluconazole decreases caffeine clearance by approximately 25%.

Likelihood Possible Evidence B
Metformin (Glucophage)

Theoretically, metformin might increase the levels and adverse effects of caffeine.
Green tea contains caffeine. Animal research suggests that metformin can reduce caffeine metabolism. Theoretically, concomitant use can increase caffeine serum concentrations and the risk of caffeine adverse effects.

Likelihood Possible Evidence D
Methoxsalen (Oxsoralen)

Theoretically, methoxsalen might increase the levels and adverse effects of caffeine.
Green tea contains caffeine. Methoxsalen can reduce caffeine metabolism. Concomitant use can increase caffeine serum concentrations and the risk of caffeine adverse effects.

Likelihood Possible Evidence B
Mexiletine (Mexitil)

Theoretically, mexiletine might increase the levels and adverse effects of caffeine.
Green tea contains caffeine. Mexiletine can decrease caffeine elimination by 50%.

Likelihood Possible Evidence B
Midazolam (Versed)

Theoretically, green tea might increase the levels and adverse effects of midazolam.
Animal research suggests that green tea extract can increase the maximum plasma concentration, but not the half-life, of oral midazolam. This effect has been attributed to the inhibition of intestinal cytochrome P450 3A4 (CYP3A4) and induction of hepatic CYP3A4 enzymes by green tea constituents. However, it is unlikely that this effect is clinically significant, as the dose used in animals was 50 times greater than what is commonly ingested by humans.

Likelihood Unlikely Evidence D
Nicardipine (Cardene)

Theoretically, green tea might increase the levels and adverse effects of nicardipine.
Green tea contains EGCG. Animal research shows that EGCG increases the area under the curve (AUC) and absolute oral bioavailability of nicardipine. The mechanism of action is thought to involve inhibition of both intestinal P-glycoprotein and hepatic cytochrome P450 3A. The effect of green tea itself on nicardipine is unclear.

Likelihood Possible Evidence D
Phenothiazines

Theoretically, phenothiazines might increase the levels and adverse effects of caffeine.
Green tea contains caffeine. Phenothiazines can reduce the metabolism of caffeine by inhibiting cytochrome P450 1A2 (CYP1A2).

Likelihood Possible Evidence D
Terbinafine (Lamisil)

Theoretically, terbinafine might increase the levels and adverse effects of caffeine.
Green tea contains caffeine. Terbinafine decreases the clearance of intravenous caffeine by 19%.

Likelihood Possible Evidence B
Tiagabine (Gabitril)

Theoretically, green tea might increase the levels and adverse effects of tiagabine.
Green tea contains caffeine. Animal research suggests that chronic caffeine administration can increase the serum concentrations of tiagabine. However, concomitant use does not seem to reduce the antiepileptic effects of tiagabine.

Likelihood Possible Evidence D
Ticlopidine (Ticlid)

Theoretically, ticlopidine might increase the levels and adverse effects of caffeine.
Green tea contains caffeine. In vitro evidence suggests that ticlopidine can inhibit caffeine metabolism. However, this effect has not been reported in humans.

Likelihood Possible Evidence D
Monograph

Green Tea: Uses, Safety & Side Effects

Medically reviewed by · Reviewed July 2026 ·
The bottom line

Green tea is a popular beverage rich in antioxidants called catechins, and drinking it in normal amounts is considered safe for most people. Concentrated green tea extracts are a different story—they may help modestly with weight or heart health for some, but high doses have been linked to rare liver problems. Talk to your pharmacist or doctor before taking green tea supplements, especially if you have liver concerns or are pregnant.

Green Tea
Scientific name
Camellia sinensis
Family
Theaceae
Part used
Leaves and leaf buds
Common forms
Brewed tea, capsules, tablets, standardized extracts, powders (matcha), and topical ointments
People commonly use it for
  • Antioxidant support
  • Weight loss
  • Heart health
  • Mental alertness
  • Cancer risk reduction

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance
OverallUse caution

Drinking green tea is generally safe, but concentrated extracts in high doses have been linked to rare liver injury.

PregnancyPossibly Safe

When used orally in moderate amounts. Due to the caffeine content of green tea, pregnant patients should closely monitor their intake to ensure modera...

Read the full pregnancy detail
BreastfeedingPossibly Safe

When used orally in moderate amounts. Due to the caffeine content of green tea, nursing parents should closely monitor caffeine intake. Breast milk co...

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Jump to a section

Overview

Green tea comes from the leaves of the Camellia sinensis plant, the same plant used to make black and oolong tea. The difference is in how the leaves are processed. Green tea leaves are steamed or pan-fired soon after picking, which keeps them from oxidizing. This gives green tea its lighter color, milder taste, and high level of natural antioxidants.

The plant is native to Asia and is widely grown in countries like China, Japan, and India. Green tea has been enjoyed as a beverage for thousands of years and is one of the most popular drinks in the world.

Today, people use green tea in many forms. Besides drinking the brewed tea, you can find it as capsules, tablets, powdered extracts, and even skin creams. Concentrated green tea extracts are often sold as supplements for weight loss or general wellness.

How it works

Green tea is rich in plant compounds called polyphenols, especially a group of antioxidants known as catechins. The most studied catechin is called EGCG (epigallocatechin gallate). Antioxidants are thought to help protect cells from damage caused by unstable molecules called free radicals.

Green tea also contains caffeine, which acts as a mild stimulant, and an amino acid called L-theanine, which may promote a calm, focused feeling.

Researchers believe the catechins and caffeine may slightly affect metabolism, fat breakdown, and blood vessel function. Most of this evidence comes from laboratory and animal studies, so it is not certain how strongly these effects apply to people drinking tea or taking supplements.

Effectiveness

Does Green Tea work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by .

Evidence overview · 80 uses evaluated
1 Likely effective 4 Possibly effective 75 Insufficient evidence
How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.
2Likely EffectiveGood evidence, though not yet conclusive.
3Possibly EffectiveSome evidence suggests a benefit.
4Possibly IneffectiveSome evidence it may not help.
5Likely IneffectiveFairly strong evidence it doesn’t help.
6IneffectiveStrong evidence it doesn’t work.
7Insufficient Reliable Evidence to RateToo little research to say either way.
Likely Effective Human papillomavirus (HPV)
Rating & evidence shown verbatim from Natural Medicines

A specific green tea extract ointment (Polyphenon E ointment 15%) is approved by the US Food and Drug Administration (FDA) for treating external genital warts caused by HPV.

Possibly Effective Cardiovascular disease (CVD)
Rating & evidence shown verbatim from Natural Medicines

Drinking green tea seems to reduce the risk of CVD and CVD-related mortality.

Possibly Effective Endometrial cancer
Rating & evidence shown verbatim from Natural Medicines

Drinking green tea seems to be beneficial for endometrial cancer prevention.

Possibly Effective Hyperlipidemia
Rating & evidence shown verbatim from Natural Medicines

Oral green tea seems to reduce levels of low-density lipoprotein (LDL) cholesterol by a small amount.

Possibly Effective Ovarian cancer
Rating & evidence shown verbatim from Natural Medicines

Drinking green tea seems to be beneficial for ovarian cancer prevention.

Also studied for 75 conditions — evidence insufficient to rate
Insufficient Reliable Evidence To Rate Acne
Rating & evidence shown verbatim from Natural Medicines

Topical green tea might reduce acne lesions by a small amount. It is unclear if oral green tea is beneficial for acne.

Insufficient Reliable Evidence To Rate Age-related cognitive decline
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for cognitive decline associated with age.

Insufficient Reliable Evidence To Rate Amyloidosis
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for amyloidosis.

Insufficient Reliable Evidence To Rate Anxiety
Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral green tea for anxiety, there is insufficient reliable information about the clinical effects of green tea for this condition.

Insufficient Reliable Evidence To Rate Athletic performance
Rating & evidence shown verbatim from Natural Medicines

The evidence on the effects of green tea constituents for athletic performance is conflicting.

Insufficient Reliable Evidence To Rate Beta-thalassemia
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for reducing iron accumulation in beta-thalassemia.

Insufficient Reliable Evidence To Rate Bladder cancer
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea is beneficial for bladder cancer prevention.

Insufficient Reliable Evidence To Rate Breast cancer
Rating & evidence shown verbatim from Natural Medicines

Evidence evaluating the association between green tea intake and breast cancer risk is inconsistent; any association may be dependent on genotype and menopausal status.

Insufficient Reliable Evidence To Rate Cervical cancer
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for cervical cancer.

Insufficient Reliable Evidence To Rate Cervical dysplasia
Rating & evidence shown verbatim from Natural Medicines

It is unclear if topical green tea is beneficial for cervical dysplasia.

Insufficient Reliable Evidence To Rate Chronic fatigue syndrome (CFS)
Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral green tea for CFS, there is insufficient reliable information about the clinical effects of green tea for this condition.

Insufficient Reliable Evidence To Rate Chronic obstructive pulmonary disease (COPD)
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea reduces the risk of COPD.

Insufficient Reliable Evidence To Rate Cognitive function
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea improves cognitive function in healthy adults.

Insufficient Reliable Evidence To Rate Cognitive impairment
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for the prevention or treatment of mild cognitive impairment in elderly adults.

Insufficient Reliable Evidence To Rate Colorectal adenoma
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea extract is beneficial for reducing colorectal adenoma recurrence.

Insufficient Reliable Evidence To Rate Colorectal cancer
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for colorectal cancer prevention.

Insufficient Reliable Evidence To Rate Crohn disease
Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral green tea for Crohn disease, there is insufficient reliable information about the clinical effects of green tea for this condition.

Insufficient Reliable Evidence To Rate Dementia
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea is beneficial for dementia prevention.

Insufficient Reliable Evidence To Rate Dental plaque
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral or topical green tea is beneficial for reducing dental plaque.

Insufficient Reliable Evidence To Rate Depression
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea is beneficial for depression prevention.

Insufficient Reliable Evidence To Rate Diabetes
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea or taking green tea extract is beneficial for the prevention of diabetes or the improvement of glycemic control.

Insufficient Reliable Evidence To Rate Diabetic neuropathy
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for improving diabetic neuropathy symptoms.

Insufficient Reliable Evidence To Rate Down syndrome
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is able to alter facial morphology in children with Down syndrome.

Insufficient Reliable Evidence To Rate Dry eye
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for improving dry eye symptoms.

Insufficient Reliable Evidence To Rate Dysmenorrhea
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea is beneficial for preventing dysmenorrhea symptoms.

Insufficient Reliable Evidence To Rate Esophageal cancer
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea is beneficial for preventing esophageal cancer; the available research is conflicting.

Insufficient Reliable Evidence To Rate Fractures
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea reduces fracture risk.

Insufficient Reliable Evidence To Rate Gastric cancer
Rating & evidence shown verbatim from Natural Medicines

Evidence evaluating an association between green tea consumption and gastric cancer risk is conflicting.

Insufficient Reliable Evidence To Rate Gingivitis
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral or topical green tea is beneficial for gingivitis.

Insufficient Reliable Evidence To Rate Headache
Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral green tea for headache, there is insufficient reliable information about the clinical effects of green tea for this condition.

Insufficient Reliable Evidence To Rate Hypertension
Rating & evidence shown verbatim from Natural Medicines

The evidence is mixed as to whether drinking green tea reduces the risk of hypertension and whether oral green tea lowers blood pressure in patients with hypertension.

Insufficient Reliable Evidence To Rate Hypotension
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for postprandial hypotension in elderly adults.

Insufficient Reliable Evidence To Rate Infertility
Rating & evidence shown verbatim from Natural Medicines

Oral green tea has only been evaluated in combination with other ingredients; its effect when used alone is unclear.

Insufficient Reliable Evidence To Rate Influenza
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for preventing the flu.

Insufficient Reliable Evidence To Rate Japanese cedar pollinosis
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for preventing Japanese cedar pollinosis symptoms.

Insufficient Reliable Evidence To Rate Kidney stones (nephrolithiasis)
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea prevents kidney stones.

Insufficient Reliable Evidence To Rate Leukemia
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea is beneficial for leukemia prevention.

Insufficient Reliable Evidence To Rate Liver cancer
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea is beneficial for liver cancer prevention.

Insufficient Reliable Evidence To Rate Lung cancer
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea is beneficial for lung cancer prevention.

Insufficient Reliable Evidence To Rate Mental alertness
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for mental alertness.

Insufficient Reliable Evidence To Rate Metabolic syndrome
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for improving metabolic parameters in people with this condition.

Insufficient Reliable Evidence To Rate Multiple myeloma
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea is beneficial for multiple myeloma prevention.

Insufficient Reliable Evidence To Rate Myocardial infarction (MI)
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea prevents MI or if drinking green tea prevents mortality in patients with a previous MI.

Insufficient Reliable Evidence To Rate Nasopharyngeal cancer
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea is beneficial for nasopharyngeal cancer prevention.

Insufficient Reliable Evidence To Rate Non-Hodgkin lymphoma
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea is beneficial for non-Hodgkin lymphoma prevention.

Insufficient Reliable Evidence To Rate Nonalcoholic fatty liver disease (NAFLD)
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for NAFLD.

Insufficient Reliable Evidence To Rate Obesity
Rating & evidence shown verbatim from Natural Medicines

Evidence for the use of green tea products for weight loss is conflicting. The conflicting findings may be related to the caffeine and catechin content of the studied products, as well as the physical activity level of the individual.

Insufficient Reliable Evidence To Rate Oral cancer
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for oral cancer prevention.

Insufficient Reliable Evidence To Rate Oral leukoplakia
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea and concomitantly applying topical green tea to lesions is beneficial for oral leukoplakia.

Insufficient Reliable Evidence To Rate Osteopenia
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for preventing osteopenia.

Insufficient Reliable Evidence To Rate Osteoporosis
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for preventing osteoporosis.

Insufficient Reliable Evidence To Rate Overall mortality
Rating & evidence shown verbatim from Natural Medicines

Some population research suggests that drinking green tea may reduce the risk of overall mortality by a small amount.

Insufficient Reliable Evidence To Rate Pancreatic cancer
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea is beneficial for pancreatic cancer prevention.

Insufficient Reliable Evidence To Rate Parkinson disease
Rating & evidence shown verbatim from Natural Medicines

Although consuming caffeinated beverages might reduce the risk of developing Parkinson disease, it is unclear if oral green tea prevents or improves symptoms in people with this condition.

Insufficient Reliable Evidence To Rate Periodontitis
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral or topical green tea is beneficial for improving oral health or improving periodontal disease.

Insufficient Reliable Evidence To Rate Pneumonia
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea is beneficial for pneumonia prevention.

Insufficient Reliable Evidence To Rate Polycystic ovary syndrome (PCOS)
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for PCOS.

Insufficient Reliable Evidence To Rate Postoperative pain
Rating & evidence shown verbatim from Natural Medicines

It is unclear if rinsing the mouth with green tea is beneficial for postoperative pain associated with molar removal.

Insufficient Reliable Evidence To Rate Prostate cancer
Rating & evidence shown verbatim from Natural Medicines

It is unclear if drinking green tea or taking green tea catechins by mouth is beneficial for prostate cancer treatment or prevention.

Insufficient Reliable Evidence To Rate Radiation dermatitis
Rating & evidence shown verbatim from Natural Medicines

It is unclear if topical green tea is beneficial for preventing radiation dermatitis.

Insufficient Reliable Evidence To Rate Radiation-induced diarrhea
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for reducing diarrhea associated with radiotherapy.

Insufficient Reliable Evidence To Rate Radiation-induced nausea and vomiting
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for reducing vomiting associated with radiotherapy.

Insufficient Reliable Evidence To Rate Renal cell carcinoma
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for preventing kidney cancer.

Insufficient Reliable Evidence To Rate Skin cancer
Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral or topical green tea for skin cancer, there is insufficient reliable information about the clinical effects of green tea for this condition.

Insufficient Reliable Evidence To Rate Stress
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for stress reduction.

Insufficient Reliable Evidence To Rate Stretch marks (striae distensae)
Rating & evidence shown verbatim from Natural Medicines

It is unclear if topical green tea is beneficial for stretch marks.

Insufficient Reliable Evidence To Rate Stroke
Rating & evidence shown verbatim from Natural Medicines

It is unclear if consumption of green tea is associated with a reduced risk of stroke or with reduced all-cause mortality in patients with a previous stroke.

Insufficient Reliable Evidence To Rate Sunburn
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral or topical green tea is beneficial for preventing ultraviolet radiation-induced erythema.

Insufficient Reliable Evidence To Rate Systemic lupus erythematosus (SLE)
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for SLE.

Insufficient Reliable Evidence To Rate Tinea pedis
Rating & evidence shown verbatim from Natural Medicines

It is unclear if a topical green tea footbath is beneficial for athlete's foot.

Insufficient Reliable Evidence To Rate Tooth extraction
Rating & evidence shown verbatim from Natural Medicines

Topical green tea has only been evaluated in combination with other ingredients; its effect when used alone is unclear.

Insufficient Reliable Evidence To Rate Ulcerative colitis
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for ulcerative colitis.

Insufficient Reliable Evidence To Rate Upper respiratory tract infection (URTI)
Rating & evidence shown verbatim from Natural Medicines

It is unclear if gargling and swallowing green tea is beneficial for reducing URTI symptoms.

Insufficient Reliable Evidence To Rate Urinary tract infections (UTIs)
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral green tea is beneficial for reducing UTI symptoms.

Insufficient Reliable Evidence To Rate Wrinkled skin
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral or topical green tea is beneficial for wrinkles.

Source & disclaimer. Effectiveness ratings and evidence summaries are provided by Natural Medicines (Therapeutic Research Center) and shown as licensed. Where Natural Medicines hasn’t rated a use, HelloPharmacist’s pharmacists may add their own reviewed rating and evidence (each such entry is labeled). This is educational information, not medical advice — talk with your pharmacist or doctor before starting, stopping, or changing a supplement.

Safety & precautions

Drinking green tea in normal amounts is considered safe for most healthy adults. The bigger concern is with concentrated green tea extracts, which deliver much higher amounts of catechins than a cup of tea.

High-dose green tea extracts have been linked in rare cases to liver injury. Taking these supplements on an empty stomach may raise this risk. People with liver disease should be especially careful and check with a healthcare provider first.

Because green tea contains caffeine, people who are sensitive to caffeine, have heart rhythm problems, anxiety, or trouble sleeping should be cautious. The same goes for people with bleeding disorders or those preparing for surgery.

Pregnancy and breastfeeding: Moderate green tea is likely okay, but pregnant people should limit caffeine. High-dose extracts should be avoided because of possible liver and caffeine concerns. While breastfeeding, caffeine passes into breast milk, so keep intake moderate and avoid concentrated supplements. When in doubt, ask your doctor or pharmacist.

Side effects

For most people, drinking green tea causes few problems. When side effects do happen, they are usually related to the caffeine content and may include:

  • Trouble sleeping or feeling jittery
  • Nervousness or anxiety
  • Upset stomach or nausea, especially on an empty stomach
  • Headache
  • Fast or irregular heartbeat

Drinking large amounts can also worsen acid reflux or cause heartburn. A rare but serious concern with concentrated green tea extract supplements is liver damage. Warning signs include yellowing of the skin or eyes, dark urine, severe stomach pain, or unusual tiredness. Stop the supplement and seek medical care right away if these occur.

Green Tea: Reported Adverse Effects

Documented safety reports on Green Tea from the evidence-graded Natural Medicines (TRC Healthcare) database, shown word-for-word from the licensed record.

Orally, green tea is generally well tolerated when consumed as a beverage in moderate amounts. Green tea extract also seems to be well tolerated when used for up to 12 months.

Most Common Adverse Effects:

Orally: Bloating, constipation, diarrhea, dyspepsia, flatulence, and nausea.

Serious Adverse Effects (Rare):

Orally: Hepatotoxicity, hypokalemia, and thrombotic thrombocytopenic purpura have been reported rarely.

Reports by condition
Allergic rhinitis (hay fever) Immunologic

Orally, matcha tea has resulted in at least one case of anaphylaxis related to green tea proteins. A 9-year-old male experienced systemic redness and hives, nausea, and anaphylaxis 60 minutes after consuming matcha tea-flavored ice cream. The caffeine found in green tea can also cause anaphylaxis in sensitive individuals, although true IgE-mediated caffeine allergy seems to be relatively rare.

  1. Kajita N, Miyama S, Kinoshita K, Yoshida K, Narita M. Green tea-induced anaphylaxis: The first pediatric case report. Allergol Int 2021;70(4):507-508.
  2. Infante S, Baeza ML, Calvo M, et al. Anaphylaxis due to caffeine. Allergy 2003;58:681-2.
Anorexia Gastrointestinal

Orally, green tea beverage or supplements can cause nausea, vomiting, abdominal bloating and pain, constipation, dyspepsia, reflux, morning anorexia, increased thirst, flatulence, and diarrhea. These effects are more common with higher doses of green tea or green tea extract, equivalent to 5-6 liters of tea per day.

  1. Pisters KM, Newman RA, Coldman B, et al. Phase I trial of oral green tea extract in adult patients with solid tumors. J Clin Oncol 2001;19:1830-8.
  2. Jatoi A, Ellison N, Burch PA, et al. A phase II trial of green tea in the treatment of patients with androgen independent metastatic prostate carcinoma. Cancer 2003;97:1442-6..
  3. Chow, H. H., Cai, Y., Hakim, I. A., Crowell, J. A., Shahi, F., Brooks, C. A., Dorr, R. T., Hara, Y., and Alberts, D. S. Pharmacokinetics and safety of green tea polyphenols after multiple-dose administration of epigallocatechin gallate and polyphenon E i
  4. Laurie, S. A., Miller, V. A., Grant, S. C., Kris, M. G., and Ng, K. K. Phase I study of green tea extract in patients with advanced lung cancer. Cancer Chemother.Pharmacol. 2005;55(1):33-38.
  5. Kalus, U., Kiesewetter, H., and Radtke, H. Effect of CYSTUS052 and green tea on subjective symptoms in patients with infection of the upper respiratory tract. Phytother.Res. 2010;24(1):96-100.
  6. Tsao, A. S., Liu, D., Martin, J., Tang, X. M., Lee, J. J., El-Naggar, A. K., Wistuba, I., Culotta, K. S., Mao, L., Gillenwater, A., Sagesaka, Y. M., Hong, W. K., and Papadimitrakopoulou, V. Phase II randomized, placebo-controlled trial of green tea extra
  7. Zheng XX, Xu YL, Li SH, et al. Green tea intake lowers fasting serum total and LDL cholesterol in adults: a meta-analysis of 14 randomized controlled trials. Am.J.Clin.Nutr. 2011;94:601-610.
  8. Jurgens, T. M., Whelan, A. M., Killian, L., Doucette, S., Kirk, S., and Foy, E. Green tea for weight loss and weight maintenance in overweight or obese adults. Cochrane.Database.Syst.Rev. 2012;12:CD008650.
  9. Crew KD, Brown P, Greenlee H, Bevers TB, Arun B, Hudis C, McArthur HL, Chang J, Rimawi M, Vornik L, Cornelison TL, Wang A, Hibshoosh H, Ahmed A, Terry MB, Santella RM, Lippman SM, Hershman DL. Phase IB randomized, double-blinded, placebo-controlled, dose
  10. Dryden GW, Lam A, Beatty K, Qazzaz HH, McClain CJ. A pilot study to evaluate the safety and efficacy of an oral dose of (-)-epigallocatechin-3-gallate-rich polyphenon E in patients with mild to moderate ulcerative colitis. Inflamm Bowel Dis. 2013 Aug;19(9
  11. Onakpoya I, Spencer E, Heneghan C, Thompson M. The effect of green tea on blood pressure and lipid profile: a systematic review and meta-analysis of randomized clinical trials. Nutr Metab Cardiovasc Dis. 2014 Aug;24:823-36.
  12. Trudel D, Labbé DP, Araya-Farias M, Doyen A, Bazinet L, Duchesne T, Plante M, Grégoire J, Renaud MC, Bachvarov D, Têtu B, Bairati I. A two-stage, single-arm, phase II study of EGCG-enriched green tea drink as a maintenance therapy in women with advanced s
  13. Zheng XX, Xu YL, Li SH, Hui R, Wu YJ, Huang XH. Effects of green tea catechins with or without caffeine on glycemic control in adults: a meta-analysis of randomized controlled trials. Am J Clin Nutr. 2013 Apr;97(4):750-62.
  14. Dostal AM, Samavat H, Bedell S, et al. The safety of green tea extract supplementation in postmenopausal women at risk for breast cancer: results of the Minnesota Green Tea Trial. Food Chem Toxicol. 2015 Sep;83:26-35.
  15. Shamekhi Z, Amani R, Habibagahi Z, Namjoyan F, Ghadiri A, Saki Malehi A. A Randomized, Double-blind, Placebo-controlled Clinical Trial Examining the Effects of Green Tea Extract on Systemic Lupus Erythematosus Disease Activity and Quality of Life. Phytoth
  16. Filippini T, Malavolti M, Borrelli F, et al. Green tea (Camellia sinensis) for the prevention of cancer. Cochrane Database Syst Rev. 2020;3(3):CD005004.
Anxiety Neurologic/CNS

Orally, green tea can cause central nervous system stimulation and adverse effects such as headache, anxiety, dizziness, insomnia, fatigue, agitation, tremors, restlessness, and confusion. These effects are more common with higher doses of green tea or green tea extract, equivalent to 5-6 liters of tea per day. The green tea constituent epigallocatechin gallate (EGCG) or decaffeinated green tea may also cause mild dizziness and headache.

Combining ephedra with caffeine can increase the risk of adverse effects. Jitteriness, hypertension, seizures, temporary loss of consciousness, and hospitalization requiring life support has been associated with the combined use of ephedra and caffeine.

Topically, green tea extract (Polyphenon E ointment) may cause headache when applied to the genital area.

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  4. Crew KD, Brown P, Greenlee H, Bevers TB, Arun B, Hudis C, McArthur HL, Chang J, Rimawi M, Vornik L, Cornelison TL, Wang A, Hibshoosh H, Ahmed A, Terry MB, Santella RM, Lippman SM, Hershman DL. Phase IB randomized, double-blinded, placebo-controlled, dose
  5. Filippini T, Malavolti M, Borrelli F, et al. Green tea (Camellia sinensis) for the prevention of cancer. Cochrane Database Syst Rev. 2020;3(3):CD005004.
  6. Chow, H. H., Cai, Y., Hakim, I. A., Crowell, J. A., Shahi, F., Brooks, C. A., Dorr, R. T., Hara, Y., and Alberts, D. S. Pharmacokinetics and safety of green tea polyphenols after multiple-dose administration of epigallocatechin gallate and polyphenon E i
  7. FDA. Proposed rule: dietary supplements containing ephedrine alkaloids. Available at: www.verity.fda.gov (Accessed 25 January 2000).
  8. Stockfleth, E., Beti, H., Orasan, R., Grigorian, F., Mescheder, A., Tawfik, H., and Thielert, C. Topical Polyphenon E in the treatment of external genital and perianal warts: a randomized controlled trial. Br.J Dermatol. 2008;158(6):1329-1338.
Anxiety Psychiatric

Green tea contains a significant amount of caffeine. Chronic use, especially in large amounts, can produce tolerance, habituation, and psychological dependence. The existence or clinical importance of caffeine withdrawal is controversial. Some researchers think that if it exists, it appears to be of little clinical significance. Other researchers suggest symptoms such as headache; tiredness and fatigue; decreased energy, alertness, and attentiveness; drowsiness; decreased contentedness; depressed mood; difficulty concentrating; irritability; and lack of clear-headedness are typical of caffeine withdrawal. Withdrawal symptoms such as delirium, nausea, vomiting, rhinorrhea, nervousness, restlessness, anxiety, muscle tension, muscle pains, and flushed face have been described. However, these symptoms may be from nonpharmacological factors related to knowledge and expectation of effects. Clinically significant symptoms caused by caffeine withdrawal may be uncommon.

  1. Institute of Medicine. Caffeine for the Sustainment of Mental Task Performance: Formulations for Military Operations. Washington, DC: National Academy Press, 2001. Available at: http://books.nap.edu/books/0309082587/html/index.html.
  2. Dews PB, O'Brien CP, Bergman J. Caffeine: behavioral effects of withdrawal and related issues. Food Chem Toxicol 2002;40:1257-61.
  3. Juliano LM, Griffiths RR. A critical review of caffeine withdrawal: empirical validation of symptoms and signs, incidence, severity, and associated features. Psychopharmacology (Berl) 2004;176:1-29.
  4. Dews PB, Curtis GL, Hanford KJ, O'Brien CP. The frequency of caffeine withdrawal in a population-based survey and in a controlled, blinded pilot experiment. J Clin Pharmacol 1999;39:1221-32.
Arrhythmia Cardiovascular

Acute or short-term oral administration of green tea may cause hypertension. The risk may be greater for green tea products containing more than 200 mg epigallocatechin gallate (EGCG). However, consumption of brewed green tea does not seem to increase blood pressure or pulse, even in mildly hypertensive patients. In fact, some evidence suggests that habitual tea consumption is associated with a reduced risk of developing hypertension. Also, epidemiological research suggests there is no association of caffeine consumption with incidence of hypertension or with cardiovascular disease mortality in patients with hypertension. Rarely, green tea consumption may cause hypotension.

Epidemiological research suggests that regular caffeine intake of up to 400 mg per day, or approximately 8 cups of green tea, is not associated with an increased incidence of atrial fibrillation, atherosclerosis, cardiac ectopy, stroke, ventricular arrhythmia, and cardiovascular disease in general.

Combining ephedra with caffeine can increase the risk of adverse effects. Jitteriness, hypertension, seizures, and temporary loss of consciousness has been associated with the combined use of ephedra and caffeine. There is also a report of ischemic stroke in an athlete who consumed ephedra 40-60 mg, creatine monohydrate 6 grams, caffeine 400-600 mg, and a variety of other supplements daily for 6 weeks. In theory, combining caffeinated green tea with ephedra would have similar effects.

In a case report, the EGCG component of a specific weight loss supplement (Hydroxycut) was thought to be responsible for atrial fibrillation. The patient was given two doses of intravenous diltiazem and was loaded with intravenous digoxin. Thirty-six hours after the last product dose, she spontaneously converted to normal sinus rhythm. The authors suggested that the block of the atrial-specific KCNA5 potassium channel likely played a role in this response.

A case of thrombotic thrombocytopenic purpura has been reported for a patient who consumed a weight loss product containing green tea. She presented at the emergency department with a one-week history of malaise, fatigue, and petechiae of the skin. Twelve procedures of plasmapheresis were performed, and corticosteroid treatment was initiated. She was discharged after 20 days.

  1. Laurie, S. A., Miller, V. A., Grant, S. C., Kris, M. G., and Ng, K. K. Phase I study of green tea extract in patients with advanced lung cancer. Cancer Chemother.Pharmacol. 2005;55(1):33-38.
  2. Miller, R. J., Jackson, K. G., Dadd, T., Mayes, A. E., Brown, A. L., and Minihane, A. M. The impact of the catechol-O-methyltransferase genotype on the acute responsiveness of vascular reactivity to a green tea extract. Br.J.Nutr. 2011;105(8):1138-1144.
  3. Miller, R. J., Jackson, K. G., Dadd, T., Mayes, A. E., Brown, A. L., Lovegrove, J. A., and Minihane, A. M. The impact of the catechol-O-methyltransferase genotype on vascular function and blood pressure after acute green tea ingestion. Mol.Nutr.Food Res.
  4. Jurgens, T. M., Whelan, A. M., Killian, L., Doucette, S., Kirk, S., and Foy, E. Green tea for weight loss and weight maintenance in overweight or obese adults. Cochrane.Database.Syst.Rev. 2012;12:CD008650.
  5. Filippini T, Malavolti M, Borrelli F, et al. Green tea (Camellia sinensis) for the prevention of cancer. Cochrane Database Syst Rev. 2020;3(3):CD005004.
  6. Onakpoya I, Spencer E, Heneghan C, Thompson M. The effect of green tea on blood pressure and lipid profile: a systematic review and meta-analysis of randomized clinical trials. Nutr Metab Cardiovasc Dis. 2014 Aug;24:823-36.
  7. Wakabayashi K, Kono S, Shinchi K, et al. Habitual coffee consumption and blood pressure: A study of self-defense officials in Japan. Eur J Epidemiol 1998;14:669-73.
  8. Hodgson JM, Puddey IB, Burke V, et al. Effects on blood pressure of drinking green and black tea. J Hypertens 1999;17:457-63.
  9. Yang YC, Lu FH, Wu JS, et al. The protective effect of habitual tea consumption on hypertension. Arch Intern Med 2004 26;164:1534-40.
  10. Winkelmayer WC, Stampfer MJ, Willett WC, Curhan GC. Habitual caffeine intake and the risk of hypertension in women. JAMA 2005;294:2330-5.
  11. Teramoto M, Yamagishi K, Muraki I, Tamakoshi A, Iso H. Coffee and green tea consumption and cardiovascular disease mortality among people with and without hypertension. J Am Heart Assoc 2023;12(2):e026477.
  12. Kalus, U., Kiesewetter, H., and Radtke, H. Effect of CYSTUS052 and green tea on subjective symptoms in patients with infection of the upper respiratory tract. Phytother.Res. 2010;24(1):96-100.
  13. Conen, D., Chiuve, S. E., Everett, B. M., Zhang, S. M., Buring, J. E., and Albert, C. M. Caffeine consumption and incident atrial fibrillation in women. Am J Clin Nutr 2010;92(3):509-514.
  14. Gronroos, N. N. and Alonso, A. Diet and risk of atrial fibrillation - epidemiologic and clinical evidence -. Circ.J 2010;74(10):2029-2038.
  15. Caldeira D, Martins C, Alves LB, Pereira H, Ferreira JJ, Costa J. Caffeine does not increase the risk of atrial fibrillation: a systematic review and meta-analysis of observational studies. Heart. 2013;99(19):1383-9. doi: 10.1136/heartjnl-2013-303950. Re
  16. Cheng M, Hu Z, Lu X, Huang J, Gu D. Caffeine intake and atrial fibrillation incidence: dose response meta-analysis of prospective cohort studies. Can J Cardiol. 2014 Apr;30(4):448-54. doi: 10.1016/j.cjca.2013.12.026. Epub 2014 2. Review.
  17. Lagier D, Nee L, Guieu R, et al. Peri-operative oral caffeine does not prevent postoperative atrial fibrillation after heart valve surgery with cardiopulmonary bypass: a randomized controlled clinical trial. Eur J Anaesthesiol. 2018 Apr 26. [Epub ahead of
  18. Voskoboinik A, Kalman JM, Kistler PM. Caffeine and arrhythmias: time to grind the data. JACC: Clin Electrophysiol. 2018;4(4):425-32.
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  20. Dixit S, Stein PK, Dewland TA, Dukes JW, Vittinghoff E, Heckbert SR, Marcus GM. Consumption of Caffeinated Products and Cardiac Ectopy. J Am Heart Assoc. 2016 26;5(1). pii: e002503. doi: 10.1161/JAHA.115.002503.
  21. Lopez-Garcia, E., Rodriguez-Artalejo, F., Rexrode, K. M., Logroscino, G., Hu, F. B., and van Dam, R. M. Coffee consumption and risk of stroke in women. Circulation 3-3-2009;119(8):1116-1123.
  22. Zuchinali P, Riberio PA, Pimentel M, da Rosa PR, Zimerman LI, Rohde LE. Effect of caffeine on ventricular arrhythmia: a systematic review and meta-analysis of experimental and clinical studies. Europace 2016 Feb;18(2):257-66.
  23. Zhang, W., Lopez-Garcia, E., Li, T. Y., Hu, F. B., and van Dam, R. M. Coffee consumption and risk of cardiovascular diseases and all-cause mortality among men with type 2 diabetes. Diabetes Care 2009;32(6):1043-1045.
  24. Wikoff D, Welsh BT, Henderson R, et al. Systematic review of the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and children. Food Chem Toxicol 2017;109:585-648.
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  26. Vahedi K, Domingo V, Amarenco P, Bousser MG. Ischemic stroke in a sportsman who consumed MaHuang extract and creatine monohydrate for bodybuilding. J Neurol Neurosurg Psychiatr 2000;68:112-3.
  27. Karth, A., Holoshitz, N., Kavinsky, C. J., Trohman, R., and McBride, B. F. A case report of atrial fibrillation potentially induced by hydroxycut: a multicomponent dietary weight loss supplement devoid of sympathomimetic amines. J.Pharm.Pract. 2010;23(3)
  28. Liatsos, G. D., Moulakakis, A., Ketikoglou, I., and Klonari, S. Possible green tea-induced thrombotic thrombocytopenic purpura. Am.J Health Syst.Pharm. 4-1-2010;67(7):531-534.
Bone loss Musculoskeletal

Orally, the ingestion of the green tea constituent epigallocatechin gallate (EGCG) or a decaffeinated green tea polyphenol mixture may cause mild muscle pain.

There is some concern regarding the association between caffeinated green tea products and osteoporosis. Epidemiological evidence regarding the relationship between caffeinated beverages such as green tea and the risk for osteoporosis is contradictory. Caffeine can increase urinary excretion of calcium. Females with a genetic variant of the vitamin D receptor appear to be at an increased risk for the detrimental effect of caffeine on bone mass. However, moderate caffeine intake of less than 400 mg per day, or about 8 cups of green tea, doesn't seem to significantly increase osteoporosis risk in most postmenopausal adults with normal calcium intake.

  1. Chow, H. H., Cai, Y., Hakim, I. A., Crowell, J. A., Shahi, F., Brooks, C. A., Dorr, R. T., Hara, Y., and Alberts, D. S. Pharmacokinetics and safety of green tea polyphenols after multiple-dose administration of epigallocatechin gallate and polyphenon E i
  2. Rapuri PB, Gallagher JC, Kinyamu HK, Ryschon KL. Caffeine intake increases the rate of bone loss in elderly women and interacts with vitamin D receptor genotypes. Am J Clin Nutr 2001;74:694-700.
  3. Massey LK. Is caffeine a risk factor for bone loss in the elderly? Am J Clin Nutr 2001;74:569-70.
  4. Massey LK, Whiting SJ. Caffeine, urinary calcium, calcium metabolism and bone. J Nutr 1993;123:1611-4.
  5. Lloyd T, Johnson-Rollings N, Eggli DF, et al. Bone status among postmenopausal women with different habitual caffeine intakes: a longitudinal investigation. J Am Coll Nutr 2000;19:256-61.
Breast cancer Endocrine

There is some concern that, due to its caffeine content, green tea may be associated with an increased risk of fibrocystic breast disease, breast cancer, and endometriosis. However, this is controversial since findings are conflicting. Restricting caffeine in females with fibrocystic breast conditions doesn't seem to affect breast nodularity, swelling, or pain.

A population analysis of the Women's Health Initiative observational study has found no association between consumption of caffeine-containing beverages, such as green tea, and the incidence of invasive breast cancer in models adjusted for demographic, lifestyle, and reproductive factors. Also, a dose-response analysis of 2 low-quality observational studies has found that high consumption of caffeine is not associated with an increased risk of breast cancer.

A case of hypoglycemia has been reported for a clinical trial participant with type 2 diabetes who used green tea in combination with prescribed antidiabetes medication.

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  2. Horner NK, Lampe JW. Potential mechanisms of diet therapy for fibrocystic breast conditions show inadequate evidence of effectiveness. J Am Diet Assoc 2000;100:1368-80.
  3. Zheng KH, Zhu K, Wactawski-Wende J, et al. Caffeine intake from coffee and tea and invasive breast cancer incidence among postmenopausal women in the Women's Health Initiative. Int J Cancer 2021;149(12):2032-2044.
  4. Wang S, Li X, Yang Y, et al. Does coffee, tea and caffeine consumption reduce the risk of incident breast cancer? A systematic review and network meta-analysis. Public Health Nutr 2021;24(18):6377-6389.
  5. Hsu, C. H., Liao, Y. L., Lin, S. C., Tsai, T. H., Huang, C. J., and Chou, P. Does supplementation with green tea extract improve insulin resistance in obese type 2 diabetics? A randomized, double-blind, and placebo-controlled clinical trial. Altern.Med.R
Cholestasis Hepatic

There is concern that some green tea products, especially green tea extracts, can cause hepatotoxicity in some patients. In 2017, the regulatory agency Health Canada re-issued a warning to consumers about this concern. The updated warning advises patients taking green tea extracts, especially those with liver disease, to watch for signs of liver toxicity. It also urges children to avoid taking products containing green tea extracts. In 2020, the United States Pharmacopeia (USP) formed an expert panel to review concerns of green tea extract-related hepatotoxicity. Based on their findings, USP determined that any products claiming compliance with USP quality standards for green tea extract must include a specific warning on the label stating "Do not take on an empty stomach. Take with food. Do not use if you have a liver problem and discontinue use and consult a healthcare practitioner if you develop symptoms of liver trouble, such as abdominal pain, dark urine, or jaundice (yellowing of the skin or eyes)".

Numerous case reports of hepatotoxicity, primarily linked to green tea extract products taken in pill form, have been published. A minimum of 29 cases have been deemed at least probably related to green tea and 38 have been deemed possibly related. In addition, elevated liver enzymes have been reported in clinical research. Most cases of toxicity have had an acute hepatitis-like presentation with a hepatocellular-elevation of liver enzymes and some cholestasis. Onset of hepatotoxic symptoms usually occurs within 3 months after initiation of the green tea extract supplement, and symptoms can persist from 10 days to 1 year. Some reports of hepatotoxicity have been associated with consumption of green tea-containing beverages as well.

In most cases, liver function returned to normal after discontinuation of the green tea product. In one case, use of a specific ethanolic green tea extract (Exolise, Arkopharma) resulted in hepatotoxicity requiring a liver transplant. Due to concerns about hepatotoxicity, this specific extract was removed from the market by the manufacturer. Since then, at least 5 cases of liver toxicity necessitating liver transplantation have been reported for patients who used green tea extracts.

There are also case reports of hepatotoxicity in green tea combined with other ingredients. In one case, use of green tea (Applied Nutrition Green Tea Fat Burner) in combination with whey protein, a nutritional supplement (GNC Mega Men Sport), and prickly pear cactus resulted in acute liver failure. Whether the hepatotoxicity in these cases is related to green tea, the other products, or their combination is unclear.

Despite the numerous reports of hepatotoxicity associated with the use of green tea products, the actual number of hepatotoxicity cases is low when the prevalence of green tea use is considered. From 2006 to 2016, liver injury from green tea products was estimated have occurred in only 1 out of 2.7 million patients who used green tea products.

In addition to the fact that green tea hepatotoxicity is uncommon, it is also not clear which patients are most likely to experience liver injury. The hepatotoxicity does not appear to be an allergic reaction or an autoimmune reaction. It is possible that certain extraction processes, for example, ethanolic extracts, produce hepatotoxic constituents. However, in most cases, the presence of contaminants in green tea products has not been confirmed in laboratory analyses.

Although results from one analysis of 4 small clinical studies disagrees, most analyses of clinical data, including one conducted by the European Food Safety Association, found that hepatotoxicity from green tea products is associated with the dose of EGCG in the green tea product. Results show that daily intake of EGCG in amounts greater than or equal to 800 mg per day is associated with a higher incidence of elevated liver enzymes such as alanine transaminase (ALT). However, it is still unclear what maximum daily dose of EGCG will not increase liver enzyme levels or what minimum daily dose of EGCG begins to cause liver injury. In many cases of liver injury, the dose of green tea extract and/or EGCG is not known. Therefore, a minimum level of green tea extract or EGCG that would cause liver injury in humans cannot be determined. Keep in mind that daily intake of green tea infusions provides only 90-300 mg of EGCG daily. So for a majority of people, green tea infusions are likely safe and unlikely to cause liver injury. Also, plasma levels of EGCG are increased when green tea catechins are taken in the fasting state, suggesting that green tea extract should be taken with food.

Until more is known, advise patients that green tea products, especially those containing green tea extract, might cause liver damage. However, let them know that the risk is uncommon, and it is not clear which products are most likely to cause the adverse effect or which patients are most likely to be affected. Advise patients with liver disease to consult their healthcare provider before taking products with green tea extract and to notify their healthcare provider if they experience symptoms of liver damage, including jaundice, dark urine, sweating, or abdominal pain.

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  7. Sarma, D. N., Barrett, M. L., Chavez, M. L., Gardiner, P., Ko, R., Mahady, G. B., Marles, R. J., Pellicore, L. S., Giancaspro, G. I., and Low, Dog T. Safety of green tea extracts : a systematic review by the US Pharmacopeia. Drug Saf 2008;31(6):469-484.
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  19. Seufferlein T, Ettrich TJ, Menzler S, et al. Green tea extract to prevent colorectal adenomas, results of a randomized, placebo-controlled clinical trial. Am J Gastroenterol 2022;117(6):884-894.
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Dental caries Pulmonary/Respiratory

A case of granulomatous alveolitis with lymph follicles has been reported for a 67-year-old female who used green tea infusions to wash her nasal cavities for 15 years. Her symptoms disappeared 2 months after stopping this practice and following an undetermined course of corticosteroids. In a case report, hypersensitivity pneumonitis was associated with inhalation of catechin-rich green tea extracts. Occupational exposure to green tea dust can cause sensitization, which may include nasal and asthmatic symptoms.

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  3. Shirai T, Hayakawa H, Akiyama J, et al. Food allergy to green tea. J Allergy Clin Immunol 2003;112:805-6.
Erythema Dermatologic

Orally, green tea may cause skin rashes or skin irritation. Topically, green tea may cause local skin reactions or skin irritation, erythema, burning, itching, edema, and erosion. A green tea extract ointment applied to the cervix can cause cervical and vaginal inflammation, vaginal irritation, and vulval burning. When applied to external genital or perianal warts, a specific green tea extract ointment (Veregen, Bradley Pharmaceuticals) providing 15% kunecatechins can cause erythema, pruritus, local pain, discomfort and burning, ulceration, induration, edema, and vesicular rash.

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  2. Zheng XX, Xu YL, Li SH, et al. Green tea intake lowers fasting serum total and LDL cholesterol in adults: a meta-analysis of 14 randomized controlled trials. Am.J.Clin.Nutr. 2011;94:601-610.
  3. Onakpoya I, Spencer E, Heneghan C, Thompson M. The effect of green tea on blood pressure and lipid profile: a systematic review and meta-analysis of randomized clinical trials. Nutr Metab Cardiovasc Dis. 2014 Aug;24:823-36.
  4. Zheng XX, Xu YL, Li SH, Hui R, Wu YJ, Huang XH. Effects of green tea catechins with or without caffeine on glycemic control in adults: a meta-analysis of randomized controlled trials. Am J Clin Nutr. 2013 Apr;97(4):750-62.
  5. Filippini T, Malavolti M, Borrelli F, et al. Green tea (Camellia sinensis) for the prevention of cancer. Cochrane Database Syst Rev. 2020;3(3):CD005004.
  6. Tzellos, T. G., Sardeli, C., Lallas, A., Papazisis, G., Chourdakis, M., and Kouvelas, D. Efficacy, safety and tolerability of green tea catechins in the treatment of external anogenital warts: a systematic review and meta-analysis. J.Eur.Acad.Dermatol.Ve
  7. Shamekhi Z, Amani R, Habibagahi Z, Namjoyan F, Ghadiri A, Saki Malehi A. A Randomized, Double-blind, Placebo-controlled Clinical Trial Examining the Effects of Green Tea Extract on Systemic Lupus Erythematosus Disease Activity and Quality of Life. Phytoth
  8. Kim S, Park TH, Kim WI, Park S, Kim JH, Cho MK. The effects of green tea on acne vulgaris: A systematic review and meta-analysis of randomized clinical trials. Phytother Res. 2021;35(1):374-383.
  9. Zhao H, Zhu W, Zhao X, et al. Efficacy of epigallocatechin-3-gallate in preventing dermatitis in patients with breast cancer receiving postoperative radiotherapy: A double-blind, placebo-controlled, phase 2 randomized clinical trial. JAMA Dermatol 2022;15
  10. Ahn WS, Yoo J, Huh SW, et al. Protective effects of green tea extracts (polyphenon E and EGCG) on human cervical lesions. Eur J Cancer Prev 2003;12:383-90.
  11. Stockfleth, E., Beti, H., Orasan, R., Grigorian, F., Mescheder, A., Tawfik, H., and Thielert, C. Topical Polyphenon E in the treatment of external genital and perianal warts: a randomized controlled trial. Br.J Dermatol. 2008;158(6):1329-1338.
  12. Gross, G., Meyer, K. G., Pres, H., Thielert, C., Tawfik, H., and Mescheder, A. A randomized, double-blind, four-arm parallel-group, placebo-controlled Phase II/III study to investigate the clinical efficacy of two galenic formulations of Polyphenon E in
  13. Bradley Pharmaceuticals. Veregen Prescribing Information. October 2006.
  14. Tatti, S., Stockfleth, E., Beutner, K. R., Tawfik, H., Elsasser, U., Weyrauch, P., and Mescheder, A. Polyphenon E: a new treatment for external anogenital warts. Br.J Dermatol. 2010;162(1):176-184.
Hypokalemia Renal

There are two cases of hypokalemia associated with drinking approximately 8 cups daily of green tea in an elderly couple of Asian descent. The hypokalemia improved after reducing their intake by 50%. It is possible that this was related to the caffeine in the green tea.

  1. Chong SJ, Howard KA, Knox C. Hypokalaemia and drinking green tea: a literature review and report of 2 cases. BMJ Case Rep. 2016;2016. pii: bcr2016214425.
DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

Adverse-effects data: Natural Medicines, Therapeutic Research Center

Dosing

There is no single official dose for green tea. As a beverage, many people drink a few cups per day without problems. For supplements, the right amount depends on the product and how concentrated it is.

Because extracts vary widely in strength, it is best to follow the directions on the product label and not exceed the recommended dose. Taking green tea extract with food rather than on an empty stomach may lower the risk of stomach upset and possibly liver problems.

If you are considering a green tea supplement, talk with your pharmacist or doctor first, especially if you have any health conditions or take other medicines. They can help you decide if it is appropriate and what amount is reasonable.

Pregnancy & Breastfeeding

Green Tea & Pregnancy

Possibly Safe

When used orally in moderate amounts. Due to the caffeine content of green tea, pregnant patients should closely monitor their intake to ensure moderate consumption. Fetal blood concentrations of caffeine approximate maternal concentrations. The use of caffeine during pregnancy is controversial; however, moderate consumption has not been associated with clinically important adverse fetal effects. In some studies consuming amounts over 200 mg daily is associated with a significantly increased risk of miscarriage. This increased risk may be most likely to occur in those with genotypes that confer a slow rate of caffeine metabolism. According to a review by Health Canada, and a subsequent large meta-analysis conducted in the US, most healthy pregnant patients can safely consume doses up to 300 mg daily without an increased risk of spontaneous abortion, stillbirth, preterm birth, fetal growth retardation, or congenital malformations. Advise keeping caffeine consumption below 300 mg daily. This is similar to the amount of caffeine in about 6 cups of green tea. Keep in mind that only the amount of ADDED caffeine must be stated on product labels. The amount of caffeine found in ingredients such as green tea, which naturally contains caffeine, does not need to be provided. This can make it difficult to determine the total amount of caffeine in a given product. Based on animal models, green tea extract catechins are also transferred to the fetus, but in amounts 50-100 times less than maternal concentrations. The potential impact of these catechins on the human fetus is not known, but animal models suggest that the catechins are not teratogenic.

  1. Briggs GB, Freeman RK, Yaffe SJ. Drugs in Pregnancy and Lactation. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 1998.
  2. The National Toxicology Program (NTP). Caffeine. Center for the Evaluation of Risks to Human Reproduction (CERHR). Available at: http://cerhr.niehs.nih.gov/common/caffeine.html.
  3. Klebanoff MA, Levine RJ, DerSimonian R, et al. Maternal serum paraxanthine, a caffeine metabolite, and the risk of spontaneous abortion. N Engl J Med 1999;341:1639-44.
  4. Eskenazi B. Caffeine—filtering the facts. N Engl J Med 1999;341:1688-9.
  5. Fernandes O, Sabharwal M, Smiley T, et al. Moderate to heavy caffeine consumption during pregnancy and relationship to spontaneous abortion and abnormal fetal growth: a meta-analysis. Reprod Toxicol 1998;12:435-44.
  6. Bracken MB, Triche EW, Belanger K, et al. Association of maternal caffeine consumption with decrements in fetal growth. Am J Epidemiol 2003;157:456-66..
  7. Nawrot P, Jordan S, Eastwood J, et al. Effects of caffeine on human health. Food Addit Contam 2003;20:1-30.
  8. Weng X, Odouli R, Li DK. Maternal caffeine consumption during pregnancy and the risk of miscarriage: a prospective cohort study. Am J Obstet Gynecol 2008;198:279.e1-8.
  9. Savitz DA, Chan RL, Herring AH, et al. Caffeine and miscarriage risk. Epidemiology 2008;19:55-62.
  10. Wikoff D, Welsh BT, Henderson R, et al. Systematic review of the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and children. Food Chem Toxicol 2017;109:585-648.
  11. Chu KO, Wang CC, Chu CY, et al. Pharmacokinetic studies of green tea catechins in maternal plasma and fetuses in rats. J Pharm Sci 2006;95:1372-81.
  12. Isbrucker RA, Edwards JA, Wolz E, et al. Safety studies on epigallocatechin gallate (EGCG) preparations. Part 3: teratogenicity and reproductive toxicity studies in rats. Food Chem Toxicol 2006;44:651-61.
Possibly Unsafe

When used orally in amounts providing more than 300 mg caffeine daily. Caffeine from green tea crosses the placenta, producing fetal blood concentrations similar to maternal levels. Consumption of caffeine in amounts over 300 mg daily is associated with a significantly increased risk of miscarriage in some studies. Advise keeping caffeine consumption from all sources below 300 mg daily. This is similar to the amount of caffeine in about 6 cups of green tea. High maternal doses of caffeine throughout pregnancy have also resulted in symptoms of caffeine withdrawal in newborn infants. High doses of caffeine have also been associated with spontaneous abortion, premature delivery, and low birth weight. However, some research has also found that intrauterine exposure to even modest amounts of caffeine, based on maternal blood levels during the first trimester, is associated with a shorter stature in children ages 4-8 years. Keep in mind that only the amount of ADDED caffeine must be stated on product labels. The amount of caffeine found in ingredients such as green tea, which naturally contains caffeine, does not need to be provided. This can make it difficult to determine the total amount of caffeine in a given product. There is also concern that consuming large amounts of green tea might have antifolate activity and potentially increase the risk of folic acid deficiency-related birth defects. Catechins in green tea inhibit the enzyme dihydrofolate reductase in vitro. This enzyme is responsible for converting folic acid to its active form. Preliminary evidence suggests that increasing maternal green tea consumption is associated with increased risk of spina bifida. Also, evidence from epidemiological research suggests that serum folate levels in pregnant patients with high green tea intake (57.3 mL per 1000 kcal) are decreased compared to participants who consume moderate or low amounts of green tea. More evidence is needed to determine the safety of using green tea during pregnancy. For now, advise pregnant patients to avoid consuming large quantities of green tea.

  1. Briggs GB, Freeman RK, Yaffe SJ. Drugs in Pregnancy and Lactation. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 1998.
  2. Weng X, Odouli R, Li DK. Maternal caffeine consumption during pregnancy and the risk of miscarriage: a prospective cohort study. Am J Obstet Gynecol 2008;198:279.e1-8.
  3. Wikoff D, Welsh BT, Henderson R, et al. Systematic review of the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and children. Food Chem Toxicol 2017;109:585-648.
  4. McGowan JD, Altman RE, Kanto WP Jr. Neonatal withdrawal symptoms after chronic maternal ingestion of caffeine. South Med J 1988;81:1092-4..
  5. Klebanoff MA, Levine RJ, DerSimonian R, et al. Maternal serum paraxanthine, a caffeine metabolite, and the risk of spontaneous abortion. N Engl J Med 1999;341:1639-44.
  6. Fernandes O, Sabharwal M, Smiley T, et al. Moderate to heavy caffeine consumption during pregnancy and relationship to spontaneous abortion and abnormal fetal growth: a meta-analysis. Reprod Toxicol 1998;12:435-44.
  7. Gleason JL, Sundaram R, Mitro SD, et al. Association of maternal caffeine consumption during pregnancy with child growth. JAMA Netw Open. 2022;5(10):e2239609.
  8. Navarro-Peran E, Cabezas-Herrera J, Garcia-Canovas F, et al. The antifolate activity of tea catechins. Cancer Res 2005;65:2059-64.
  9. Correa A, Stolley A, Liu Y. Prenatal tea consumption and risks of anencephaly and spina bifida. Ann Epidemiol 2000;10:476-7.
  10. Shiraishi M, Haruna M, Matsuzaki M, Ota E, Murayama R, Murashima S. Association between the serum folate levels and tea consumption during pregnancy. Biosci Trends. 2010 Oct;4(5):225-30.

Green Tea & Breastfeeding

Possibly Safe

When used orally in moderate amounts. Due to the caffeine content of green tea, nursing parents should closely monitor caffeine intake. Breast milk concentrations of caffeine are thought to be approximately 50% of maternal serum concentrations.

  1. Nehlig A, Debry G. Consequences on the newborn of chronic maternal consumption of coffee during gestation and lactation: a review. J Am Coll Nutr 1994;13:6-21..
Possibly Unsafe

When used orally in large amounts. Consumption of green tea might cause irritability and increased bowel activity in nursing infants. There is insufficient reliable information available about the safety of green tea extracts when applied topically during breast-feeding.

  1. American Academy of Pediatrics. The transfer of drugs and other chemicals into human milk. Pediatrics 2001;108:776-89.
DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

© 2026 Therapeutic Research Center

Pregnancy & lactation ratings: Natural Medicines, Therapeutic Research Center

References & further reading

The 219 references that drive our Green Tea monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
  2. Harder S, Fuhr U, Staib AH, Wolff T. Ciprofloxacin-caffeine: a drug interaction established using in vivo and in vitro investigations. Am J Med 1989;87:89S-91S. PubMed
  3. Carbo M, Segura J, De la Torre R, et al. Effect of quinolones on caffeine disposition. Clin Pharmacol Ther 1989;45:234-40. PubMed
  4. Healy DP, Polk RE, Kanawati L, et al. Interaction between oral ciprofloxacin and caffeine in normal volunteers. Antimicrob Agents Chemother 1989;33:474-8. PubMed
  5. Mester R, Toren P, Mizrachi I, et al. Caffeine withdrawal increases lithium blood levels. Biol Psychiatry 1995;37:348-50. PubMed
  6. Jefferson JW. Lithium tremor and caffeine intake: two cases of drinking less and shaking more. J Clin Psychiatry 1988;49:72-3.
  7. Mitscher LA, Mitscher LA, Jung M, Shankel D, et al. Chemoprotection: a review of the potential therapeutic antioxidant properties of green tea (Camellia sinensis) and certain of its constituents. Med Res Rev 1997;17:327-65.
  8. Joeres R, Klinker H, Heusler H, et al. Influence of mexiletine on caffeine elimination. Pharmacol Ther 1987;33:163-9. PubMed
  9. Vahedi K, Domingo V, Amarenco P, Bousser MG. Ischemic stroke in a sportsman who consumed MaHuang extract and creatine monohydrate for bodybuilding. J Neurol Neurosurg Psychiatr 2000;68:112-3.
  10. Wakabayashi K, Kono S, Shinchi K, et al. Habitual coffee consumption and blood pressure: A study of self-defense officials in Japan. Eur J Epidemiol 1998;14:669-73. PubMed
  11. Hodgson JM, Puddey IB, Burke V, et al. Effects on blood pressure of drinking green and black tea. J Hypertens 1999;17:457-63. PubMed
  12. Booth SL, Madabushi HT, Davidson KW, et al. Tea and coffee brews are not dietary sources of vitamin K-1 (phylloquinone). J Am Diet Assoc 1995;95:82-3. PubMed
  13. Lou FQ, Zhang MF, Zhang XG, et al. A study on tea-pigment in prevention of atherosclerosis. Chin Med J (Engl) 1989;102:579-83.
  14. Graham HN. Green tea composition, consumption, and polyphenol chemistry. Prev Med 1992;21:334-50. PubMed
  15. Rapuri PB, Gallagher JC, Kinyamu HK, Ryschon KL. Caffeine intake increases the rate of bone loss in elderly women and interacts with vitamin D receptor genotypes. Am J Clin Nutr 2001;74:694-700. PubMed
Keep reading

This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Brand directory

Brands that make products with Green Tea

1,611 brands in our database make a supplement containing Green Tea.

Product directory

Supplement products with Green Tea

9,344 products in our database contain Green Tea. Open any to see its full ingredient list and every drug interaction we check.

"The Original" HerbaGreen Tea by HerbaSway Liquid 2 fl. Oz. View ingredients & interactions (C)Lean Boost 495 mg by Jane Health Capsule 120 Capsule(s) View ingredients & interactions +Energy CorEnergy by Shaklee Capsule 90 Capsule(s) View ingredients & interactions +PlusShake Raw Chocolate by Greens+ Powder 1.5 lb · 677 Gram(s) View ingredients & interactions +PlusShake Raw Vanilla by Greens+ Powder 1.5 lb · 661 Gram(s) View ingredients & interactions 01-02 Enhanced Fat Melting Matrix by ATS Labs Capsule 60 Capsule(s) View ingredients & interactions 1 Before Packet by New Earth Edge Capsule 14 Packet(s) View ingredients & interactions 1 Before Packet by New Earth Edge Capsule 60 Packet(s) View ingredients & interactions 1-Db Goddess by 1st Phorm Capsule 80 Capsule(s) View ingredients & interactions 1-Db Overdrive by 1st Phorm Capsule 80 Capsule(s) View ingredients & interactions 10 Berry by LXR Biotech Liquid 1.93 fl. Oz. · 57 mL View ingredients & interactions 10 Berry by LXR Biotech Liquid 12 {Bottle(s)} View ingredients & interactions 10 Grape by LXR Biotech Liquid View ingredients & interactions 10 Grape by LXR Biotech Liquid 12 {Bottle(s)} View ingredients & interactions 100% Pure African Mango 150 mg by Infiniti Creations Capsule 60 Capsule(s) View ingredients & interactions 100% Pure Garcinia Cambogia Drops by Infiniti Creations Liquid 2 Fluid Ounce(s) · 60 mL View ingredients & interactions 100% Pure Green Coffee Bean Drops by Infiniti Creations Liquid 2 Fluid Ounce(s) · 60 mL View ingredients & interactions 100% Pure Maqui Berry by Infiniti Creations Capsule 60 Capsule(s) View ingredients & interactions 100% Pure Raspberry Ketones by Infiniti Creations Capsule 60 Capsule(s) View ingredients & interactions 100% Pure Raspberry Keytones Drops by Infiniti Creations Liquid 2 Fluid Ounce(s) · 60 mL View ingredients & interactions 100% Vegan Complete MultiVitamin by Purely Inspired Tablet Or Pill 90 Vegan Tablet(s) View ingredients & interactions 10X Life by Max Drive Nutrition Capsule 60 Capsule(s) View ingredients & interactions 14-Day Fat Burn Cleanse by Applied Nutrition Tablet Or Pill 56 Tablet(s) View ingredients & interactions 1650 mg Glutathione Complex by Relumins Advance White Capsule 90 Vegetarian Capsule(s) View ingredients & interactions
Pharmacist Counseling Corner

Green Tea: Common Questions

What is Green Tea used for, and does it work?
People use Green Tea for many reasons, but the evidence varies by use. According to the Natural Medicines database, there is at least some clinical evidence supporting Green Tea for Human papillomavirus (HPV), Cardiovascular disease (CVD), Endometrial cancer and Hyperlipidemia. For most other uses it has been studied for, the evidence is currently insufficient to rate. See the graded list on this page, and always confirm with your pharmacist or doctor.
Does Green Tea interact with prescription medications?
Yes. We list 1293 medications with a known interaction with Green Tea, including 13 rated major. Use the checker above to see how Green Tea interacts with a specific drug.
How are Green Tea interactions rated?
Each interaction is graded major, moderate, or minor based on how clinically significant it is and the strength of the evidence behind it. Major interactions are the most serious and are best avoided, or used only under close professional supervision.
Is it safe to take Green Tea with my medications?
It depends on the specific medication. Some combinations are fine, while others call for monitoring, timing changes, or should be avoided. Check your exact drug above and confirm with your pharmacist or doctor before starting, stopping, or changing anything.
Where does this Green Tea interaction information come from?
Our interaction data is built on the Natural Medicines database — an evidence-graded reference for vitamins, herbs, and supplements — and is reviewed by licensed HelloPharmacist pharmacists, who may add clinical context.
Is it better to drink Green Tea or take a Green Tea extract supplement?
For most people, drinking Green Tea is the safer choice and provides antioxidants along with hydration. Concentrated extracts have been linked in rare cases to liver injury, so use them only with care and ideally after talking to a healthcare provider.
How much caffeine is in Green Tea?
A cup of Green Tea typically contains less caffeine than coffee, but the exact amount depends on the type and how long it is brewed. If you are sensitive to caffeine, you may want to choose decaffeinated Green Tea.
Can Green Tea help me lose weight?
Green Tea and its extract may lead to small reductions in body weight for some people, but the effect is modest and not guaranteed. It works best alongside a healthy diet and exercise, not as a replacement for them.
Is Green Tea safe during pregnancy?
Moderate amounts of Green Tea are likely fine, but pregnant people should limit caffeine and avoid high-dose Green Tea extract supplements. Check with your doctor about how much is safe for you.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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