Herb & supplement monograph

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

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Oolong Tea interacts with medications. The heart of this page is the interaction list — every drug Oolong 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 Oolong 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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Oolong 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 Oolong Tea drug interaction appears low for most people, since nearly every concern traces back to the ordinary caffeine the tea contains. Only a small number of the many listed interactions are rated major, and most of the rest are moderate concerns that remain theoretical.

Interactions deserving the most attention

The clearest warning is with ephedrine and other stimulant drugs, where adding caffeine has been linked to dangerous rises in blood pressure and, rarely, heart attack, stroke, or seizures. Caffeine can also raise clozapine levels and worsen its side effects, and suddenly stopping regular tea intake may increase lithium levels and tremor. Animal research suggests heavy caffeine intake could weaken some seizure medicines, while drugs like cimetidine and fluvoxamine slow caffeine clearance and can amplify its jittery, stimulating effects.

What the rest of the list means

A long list like this mostly reflects one shared ingredient, caffeine, and its possible effects on an enzyme the body uses to clear certain medications. Many entries rest on lab or animal findings only, and several predicted effects have not been shown to cause meaningful problems in people.

Check your medications against Oolong Tea

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

Interaction report

Drugs that interact with Oolong Tea

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

8 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 Oolong Tea.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Oolong Tea using our pharmacist-reviewed interaction data.

AI summaries are generated from our Oolong Tea interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

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 Oolong 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 Oolong Tea affects

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

All 37 drug categories Oolong Tea interacts with

EphedrineAdenosine (adenocard)Anticoagulant/antiplatelet DrugsBeta-adrenergic AgonistsCimetidine (tagamet)Clozapine (clozaril)Cytochrome P450 1a2 (cyp1a2) InhibitorsDipyridamole (persantine)Disulfiram (antabuse)Diuretic DrugsEstrogensFlutamide (eulexin)Fluvoxamine (luvox)LithiumMonoamine Oxidase Inhibitors (maois)NicotinePentobarbital (nembutal)Phenobarbital (luminal)PhenylpropanolaminePhenytoin (dilantin)Pioglitazone (actos)Riluzole (rilutek)Stimulant DrugsTheophyllineValproateVerapamil (calan, Others)Alcohol (ethanol)Antidiabetes DrugsContraceptive DrugsFluconazole (diflucan)Methoxsalen (oxsoralen)Mexiletine (mexitil)PhenothiazinesQuinolone AntibioticsTerbinafine (lamisil)Tiagabine (gabitril)Ticlopidine (ticlid)

Ephedrine

Theoretically, concomitant use might increase the risk for stimulant adverse effects.
Oolong 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. Tell patients to avoid taking caffeine with ephedrine and other stimulants.

Likelihood Probable Evidence D

Adenosine (Adenocard)

Theoretically, oolong tea might decrease the vasodilatory effects of adenosine and interfere with its use prior to stress testing.
Oolong tea contains caffeine. Caffeine is a competitive inhibitor of adenosine at the cellular level. However, caffeine does not seem to affect supplemental adenosine because high interstitial levels of adenosine overcome the antagonistic effects of caffeine. It is recommended that methylxanthines such as caffeine, as well as 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, oolong tea might increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Oolong tea contains caffeine. Caffeine is reported to have antiplatelet activity. Theoretically, the caffeine in oolong tea might increase the risk of bleeding when used concomitantly with these agents. However, this interaction has not been reported in humans.

Likelihood Possible Evidence D

Beta-Adrenergic Agonists

Theoretically, large amounts of oolong tea might increase the cardiac inotropic effects of beta-agonists.
Oolong tea contains caffeine. Caffeine can increase cardiac inotropic effects of beta-agonists.

Likelihood Probable Evidence D

Cimetidine (Tagamet)

Theoretically, concomitant use might increase the effects and adverse effects of caffeine in oolong tea.
Oolong tea contains caffeine. Cimetidine can reduce the rate of caffeine clearance by 30% to 50%.

Likelihood Likely Evidence B

Clozapine (Clozaril)

Theoretically, oolong tea might increase the levels and adverse effects of clozapine and acutely exacerbate psychotic symptoms.
Oolong tea contains caffeine. Caffeine can increase the effects and toxicity of clozapine. Caffeine doses of 400-1000 mg per day 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

Cytochrome P450 1A2 (Cyp1A2) Inhibitors

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

Likelihood Possible Evidence D

Dipyridamole (Persantine)

Theoretically, oolong tea might decrease the vasodilatory effects of dipyridamole and interfere with its use prior to stress testing.
Oolong tea contains caffeine. Caffeine is a methylxanthine that may inhibit dipyridamole-induced vasodilation. It is recommended that methylxanthines such as caffeine, as well as methylxanthine-containing products such as oolong tea, be stopped 24 hours prior to pharmacological stress tests. Methylxanthines appear more likely to interfere with dipyridamole than adenosine-induced stress testing.

Likelihood Probable Evidence B

Disulfiram (Antabuse)

Theoretically, disulfiram might increase the risk of adverse effects from caffeine in oolong tea.
Oolong tea contains caffeine. Disulfiram decreases the clearance and increases the half-life of caffeine.

Likelihood Probable Evidence D

Diuretic Drugs

Theoretically, using oolong tea with diuretic drugs might increase the risk of hypokalemia.
Oolong 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 in oolong tea.
Oolong tea contains caffeine. Estrogen inhibits caffeine metabolism.

Likelihood Probable Evidence B

Flutamide (Eulexin)

Theoretically, oolong tea might increase the levels and adverse effects of flutamide.
Oolong tea contains caffeine. In vitro evidence suggests that caffeine can inhibit the metabolism of flutamide.

Likelihood Possible Evidence D

Fluvoxamine (Luvox)

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

Likelihood Probable Evidence D

Lithium

Theoretically, abrupt oolong tea withdrawal might increase the levels and adverse effects of lithium.
Oolong tea contains caffeine. Abrupt caffeine withdrawal can increase serum lithium levels, worsening lithium tremor.

Likelihood Probable Evidence D

Monoamine Oxidase Inhibitors (Maois)

Theoretically, concomitant use might increase the risk of a hypertensive crisis.
Oolong tea contains caffeine. Caffeine has been shown to inhibit MAO A and B in laboratory studies. Concomitant intake of large amounts of caffeine with MAOIs might precipitate a hypertensive crisis.

Likelihood Possible Evidence D

Nicotine

Theoretically, concomitant use might increase the risk of hypertension.
Oolong 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

Pentobarbital (Nembutal)

Theoretically, caffeine in oolong tea might decrease the effects of pentobarbital.
Oolong tea contains caffeine. The caffeine in oolong tea might negate the hypnotic effects of pentobarbital.

Likelihood Possible Evidence B

Phenobarbital (Luminal)

Theoretically, oolong tea might reduce the effects of phenobarbital and increase the risk for convulsions.
Oolong 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 in oolong tea.
Oolong 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, oolong tea might reduce the effects of phenytoin and increase the risk for convulsions.
Oolong 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, oolong tea might increase the levels and clinical effects of pioglitazone.
Oolong 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

Riluzole (Rilutek)

Theoretically, concomitant use might increase the levels and adverse effects of both caffeine and riluzole.
Oolong tea contains caffeine. Caffeine and riluzole are both metabolized by cytochrome P450 1A2 (CYP1A2), and concomitant use might reduce metabolism of one or both agents.

Likelihood Possible Evidence D

Stimulant Drugs

Theoretically, concomitant use might increase stimulant adverse effects.
Oolong tea contains caffeine. Due to the CNS stimulant effects of the caffeine constituent of oolong tea, concomitant use with stimulant drugs can increase the risk of adverse effects.

Likelihood Probable Evidence C

Theophylline

Theoretically, oolong tea might increase the levels and adverse effects of theophylline.
Oolong tea contains caffeine. Caffeine decreases theophylline clearance 23% to 29%.

Likelihood Probable Evidence D

Valproate

Theoretically, oolong tea might reduce the effects of valproate and increase the risk for convulsions.
Oolong 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 caffeine in oolong tea.
Oolong tea contains caffeine. Verapamil increases plasma caffeine concentrations by 25%.

Likelihood Possible Evidence D

Alcohol (Ethanol)

Theoretically, alcohol might increase the levels and adverse effects of caffeine in oolong tea.
Oolong 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 oolong tea with antidiabetes drugs might interfere with blood glucose control.
Oolong tea contains caffeine. Reports claim that caffeine might increase or decrease blood glucose levels.

Likelihood Unlikely Evidence B

Contraceptive Drugs

Theoretically, concomitant use might increase the effects and adverse effects of caffeine in oolong tea.
Oolong tea contains caffeine. Oral contraceptives decrease the rate of caffeine clearance by 40% to 65%.

Likelihood Possible Evidence B

Fluconazole (Diflucan)

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

Likelihood Possible Evidence B

Methoxsalen (Oxsoralen)

Theoretically, methoxsalen might increase the levels and adverse effects of caffeine in oolong tea.
Oolong tea contains caffeine. Methoxsalen can reduce caffeine metabolism.

Likelihood Possible Evidence B

Mexiletine (Mexitil)

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

Likelihood Possible Evidence B

Phenothiazines

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

Likelihood Possible Evidence D

Quinolone Antibiotics

Theoretically, quinolone antibiotics might increase the levels and adverse effects of caffeine in oolong tea.
Oolong tea contains caffeine. Quinolones decrease caffeine clearance.

Likelihood Possible Evidence B

Terbinafine (Lamisil)

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

Likelihood Possible Evidence B

Tiagabine (Gabitril)

Theoretically, oolong tea might increase the levels and adverse effects of tiagabine.
Oolong 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 in oolong tea.
Oolong 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

Oolong Tea: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

Oolong tea is a traditional partially oxidized tea made from the same plant as green and black tea, and it provides caffeine and plant antioxidants. As a beverage it is generally considered safe for most healthy adults in moderate amounts, but evidence for specific health benefits like weight loss or blood sugar control is limited. If you have heart, blood pressure, or caffeine-sensitivity concerns, talk with your pharmacist or doctor.

Scientific name: Camellia sinensis
Family: Theaceae
Part used: Leaves (partially oxidized)
Common forms: Brewed tea, tea bags, loose leaf, extract capsules, powders

People commonly use it for

Weight management
Mental alertness and energy
Heart health
Blood sugar support
Antioxidant support

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

Safety at a glance

OverallLikely safe

Generally safe for most healthy adults when consumed as a beverage in moderate amounts.

PregnancyPossibly Safe

When used orally in moderate amounts. Due to the caffeine content of oolong tea, mothers should closely monitor their intake to ensure moderate consum...

Read the full pregnancy detail

BreastfeedingPossibly Safe

When used orally in moderate amounts. Due to the caffeine content of oolong tea, caffeine intake should be closely monitored. Breast milk concentratio...

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

Oolong tea is a traditional tea made from the leaves of the Camellia sinensis plant — the same plant used to make green and black tea. What makes oolong different is how it is processed. The leaves are partially oxidized (allowed to react with air), which places oolong somewhere between green tea (less oxidized) and black tea (fully oxidized) in flavor and color.

Oolong is most strongly associated with China and Taiwan, where it has been grown and enjoyed for centuries. It is usually consumed as a hot or cold brewed beverage, but it is also sold as extract capsules and powders marketed for weight loss and general wellness.

Like other true teas, oolong naturally contains caffeine and plant compounds called polyphenols, which is why people drink it for both flavor and possible health perks.

How it works

Oolong tea contains several compounds thought to be responsible for its effects. The most studied are caffeine and polyphenols, including catechins and theaflavins formed during oxidation.

Caffeine is a stimulant that can increase alertness and slightly raise metabolism. Polyphenols act as antioxidants in laboratory settings, meaning they can neutralize unstable molecules called free radicals. Oolong also contains L-theanine, an amino acid that may promote a calm, focused feeling.

It is important to know that much of the research on these compounds comes from laboratory and animal studies, or from observing large groups of tea drinkers. These findings do not always translate into clear, proven benefits for people drinking tea every day.

Effectiveness

Does Oolong Tea work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 14 uses evaluated

1 Likely effective 13 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 Mental alertness

Rating & evidence shown verbatim from Natural Medicines

Consumption of caffeine-containing beverages, such as oolong tea, can improve or attenuate declines in mental alertness and cognitive capacity.

Also studied for 13 conditions — evidence insufficient to rate

Insufficient Reliable Evidence To Rate Atopic dermatitis (eczema)

Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral oolong tea is beneficial in patients with atopic dermatitis.

Insufficient Reliable Evidence To Rate Autism spectrum disorder

Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral oolong tea is beneficial in children with autism spectrum disorder.

Insufficient Reliable Evidence To Rate Cardiovascular disease (CVD)

Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral oolong tea for prevention of CVD or CVD-related events, there is insufficient reliable information about the clinical effects of oolong tea for this purpose.

Insufficient Reliable Evidence To Rate Chronic obstructive pulmonary disease (COPD)

Rating & evidence shown verbatim from Natural Medicines

It is unclear if oolong tea is associated with a reduced risk of COPD.

Insufficient Reliable Evidence To Rate Depression

Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral oolong tea is beneficial for depression in older adults.

Insufficient Reliable Evidence To Rate Diabetes

Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral oolong tea is beneficial for the treatment or prevention of diabetes.

Insufficient Reliable Evidence To Rate Dysmenorrhea

Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral oolong tea is beneficial for the treatment or prevention of dysmenorrhea.

Insufficient Reliable Evidence To Rate Hyperlipidemia

Rating & evidence shown verbatim from Natural Medicines

Although there has been interest in using oral oolong tea for hyperlipidemia, there is insufficient reliable information about the clinical effects of oolong tea for this purpose.

Insufficient Reliable Evidence To Rate Hypertension

Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral oolong tea is beneficial for the prevention of hypertension.

Insufficient Reliable Evidence To Rate Obesity

Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral oolong tea is beneficial in patients with obesity.

Insufficient Reliable Evidence To Rate Oral cancer

Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral oolong tea is beneficial for preventing oral squamous cell carcinoma.

Insufficient Reliable Evidence To Rate Osteoporosis

Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral oolong tea is beneficial for the prevention of osteoporosis.

Insufficient Reliable Evidence To Rate Ovarian cancer

Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral oolong tea is beneficial for preventing ovarian cancer.

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

For most healthy adults, oolong tea is generally safe when consumed as a beverage in moderate amounts. The main concern is its caffeine content, which can cause problems in people who are sensitive to it or who drink large amounts.

Use extra caution if you have heart problems, irregular heartbeat, high blood pressure, anxiety, acid reflux, or trouble sleeping. People with iron-deficiency anemia should know that tea can reduce iron absorption, so it is best to drink tea between meals rather than with iron-rich foods or supplements.

Pregnancy: Caffeine crosses the placenta, and most experts recommend limiting total caffeine during pregnancy. Talk with your doctor about a safe amount, and treat oolong as a source of caffeine to count.

Breastfeeding: Caffeine passes into breast milk and may make some babies fussy or wakeful. Keep intake modest and watch how your baby responds.

Concentrated oolong extract supplements are different from brewed tea — they can deliver much higher doses of caffeine and polyphenols, and their safety is less well studied. Check with your pharmacist before using extracts.

Side effects

Most side effects come from caffeine, especially when you drink a lot. These can include jitteriness, anxiety, a fast or pounding heartbeat, trouble sleeping, headache, upset stomach, and the need to urinate more often.

Drinking tea on an empty stomach may cause nausea or stomach discomfort in some people. Very high tea intake can also reduce iron absorption over time.

Serious problems are rare with normal tea drinking. Concentrated green and oolong tea extract supplements have, in rare cases, been linked to liver injury, so see a doctor if you develop symptoms like yellowing skin, dark urine, or persistent abdominal pain while using such products.

Oolong Tea: Reported Adverse Effects

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

Orally, oolong tea is well tolerated when consumed as a beverage in moderate amounts.

Most Common Adverse Effects:

Orally: Many of the adverse effects of oolong tea can be attributed to its caffeine content, such as insomnia, nervousness, restlessness, tachycardia, tachypnea, and tremors.

Serious Adverse Effects (Rare):

Orally: Many of the serious adverse effects of oolong tea can be attributed to its caffeine content, such as arrhythmia, chest pain, convulsions, delirium, premature heartbeat, and respiratory alkalosis.

Reports by condition

Allergic rhinitis (hay fever) Immunologic

Oolong tea contains caffeine. Caffeine can cause anaphylaxis in sensitive individuals, although true IgE-mediated caffeine allergy seems to be relatively rare.

Infante S, Baeza ML, Calvo M, et al. Anaphylaxis due to caffeine. Allergy 2003;58:681-2.

Anemia Endocrine

Oolong tea contains caffeine. Large doses of caffeine can cause massive catecholamine release and subsequent metabolic acidosis, hyperglycemia, and ketosis.

Some evidence has found that caffeine is associated with fibrocystic breast disease, breast cancer, and endometriosis in women. However, a population analysis of the Women's Health Initiative observational study suggests that there is no association between consumption of caffeine-containing beverages 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 suggests that high consumption of caffeine is not associated with an increased risk of breast cancer. Restricting caffeine in women with fibrocystic breast conditions doesn't seem to affect breast nodularity, swelling, or pain. In infants, tea may cause microcytic anemia.

Anxiety Neurologic/CNS

Oolong tea contains caffeine. Orally, caffeine can cause insomnia, nervousness, headache, anxiety, agitation, jitteriness, restlessness, ringing in the ears, tremors, delirium, and convulsions. Caffeine may also exacerbate sleep disturbances in patients with acquired immunodeficiency syndrome (AIDS).

There is some concern that stopping regular use of caffeine may cause withdrawal symptoms such as headache, tiredness and fatigue, drowsiness, depressed mood, difficulty concentrating, irritability, and decreased energy, alertness, and attentiveness. Other symptoms such as delirium, nervousness, restlessness, and anxiety have been described. However, these symptoms may be from nonpharmacological factors related to knowledge and expectation of effects.

Schechter MD, Timmons GD. Objectively measured hyperactivity--II. Caffeine and amphetamine effects. J Clin Pharmacol 1985;25:276-80..
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.
Holmgren P, Norden-Pettersson L, Ahlner J. Caffeine fatalities--four case reports. Forensic Sci Int 2004;139:71-3.
Leson CL, McGuigan MA, Bryson SM. Caffeine overdose in an adolescent male. J Toxicol Clin Toxicol 1988;26:407-15.
Dreher HM. The effect of caffeine reduction on sleep quality and well-being in persons with HIV. J Psychosom Res 2003;54:191-8..
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.
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.
Dews PB, O'Brien CP, Bergman J. Caffeine: behavioral effects of withdrawal and related issues. Food Chem Toxicol 2002;40:1257-61.

Arrhythmia Cardiovascular

Orally, oolong tea can cause some cardiovascular-related adverse effects. Some of these effects may be due to the caffeine content of oolong tea. Acute oral administration of caffeine can cause increased blood pressure, but regular consumption does not seem to increase either blood pressure or pulse, even in mildly hypertensive patients. Also, epidemiological research suggests that there is no association of caffeine consumption with incidence of hypertension. Epidemiological research also suggests that regular caffeine intake of up to 400 mg per day, or approximately 4 cups of tea, is not associated with an increased incidence of atrial fibrillation, atherosclerosis, cardiac ectopy, stroke, ventricular arrhythmia, or cardiovascular disease in general.

However, due to its caffeine content, oolong tea may cause other adverse cardiovascular effects when used orally. These effects include tachycardia, tachypnea, chest pain, premature heartbeat, arrhythmia, and hypertension. Large doses of caffeine can cause massive catecholamine release and subsequent sinus tachycardia.

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. 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 six weeks.

Bone loss Musculoskeletal

Oolong tea contains caffeine. Some epidemiological research has found that caffeine may be associated with an increased risk of osteoporosis, but conflicting evidence exists. Caffeine can increase urinary excretion of calcium. Women identified 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 4 cups of tea, does not seem to significantly increase osteoporosis risk in most postmenopausal women with normal calcium intake.

Some researchers believe that stopping regular use of caffeine may cause withdrawal symptoms such as muscle tension and muscle pains. However, these symptoms may be from nonpharmacological factors related to knowledge and expectation of effects.

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 official standardized dose of oolong tea. Most people simply drink it as a beverage — typically one to several cups per day brewed from tea bags or loose leaves.

For extract capsules and powders, a single best dose has not been established, and products vary widely in strength and caffeine content. The safest approach is to follow the directions on the product label and not exceed them.

Keep your total daily caffeine in mind, especially if you also drink coffee, other teas, or energy drinks. If you are pregnant, breastfeeding, or have a health condition, check with your pharmacist or doctor before using concentrated oolong supplements.

Pregnancy & Breastfeeding

Oolong Tea & Pregnancy

Possibly Safe

When used orally in moderate amounts. Due to the caffeine content of oolong tea, mothers should closely monitor their intake to ensure moderate consumption. Fetal blood concentrations of caffeine approximate maternal concentrations. Use of caffeine in 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 adults can safely consume doses up to 300 mg daily during pregnancy without an increased risk of spontaneous abortion, stillbirth, preterm birth, fetal growth retardation, or congenital malformations. Advise keeping caffeine consumption below 300 mg daily during pregnancy. This is similar to the amount of caffeine found in about 3 cups of tea. There is also some evidence to suggest that a component found in oolong tea may inhibit folate metabolism and decrease folic acid concentrations during pregnancy. Folic acid levels should be monitored closely.

Briggs GB, Freeman RK, Yaffe SJ. Drugs in Pregnancy and Lactation. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 1998.
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.
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.
Eskenazi B. Caffeine—filtering the facts. N Engl J Med 1999;341:1688-9.
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.
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..
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.
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.
Nawrot P, Jordan S, Eastwood J, et al. Effects of caffeine on human health. Food Addit Contam 2003;20:1-30.
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;4(5):225-30.

Possibly Unsafe

When used orally in large amounts. Caffeine from oolong tea crosses the placenta, producing fetal blood concentrations similar to maternal levels. In a cohort of mother/infant pairs with a median maternal plasma caffeine level of 168.5 ng/mL (range 29.5-650.5 ng/mL) during pregnancy, birth weights and lengths were lower in the 4th quartile of caffeine intake compared with the 1st. By age 7, heights and weights were lower by 1.5 cm and 1.1 kg respectively. In another cohort of mother/infant pairs with higher maternal pregnancy plasma caffeine levels, median 625.5 ng/mL (range 86.2 to 1994.7 ng/mL), heights at age 8 were 2.2 cm lower, but there was no difference in weights. 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 during pregnancy. This is similar to the amount of caffeine in about 3 cups of tea. High maternal doses of caffeine throughout pregnancy have 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.

Oolong Tea & Breastfeeding

Possibly Safe

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

Possibly Unsafe

When used orally in large amounts. Consumption of oolong tea might cause irritability and increased bowel activity in nursing infants. Large doses or excessive intake of oolong tea should be avoided during lactation.

American Academy of Pediatrics. The transfer of drugs and other chemicals into human milk. Pediatrics 2001;108:776-89.

Pregnancy & lactation ratings: Natural Medicines, Therapeutic Research Center

References & further reading

The 112 references that drive our Oolong 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.

McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
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
Carbo M, Segura J, De la Torre R, et al. Effect of quinolones on caffeine disposition. Clin Pharmacol Ther 1989;45:234-40. PubMed
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
Mester R, Toren P, Mizrachi I, et al. Caffeine withdrawal increases lithium blood levels. Biol Psychiatry 1995;37:348-50. PubMed
Jefferson JW. Lithium tremor and caffeine intake: two cases of drinking less and shaking more. J Clin Psychiatry 1988;49:72-3.
Merhav H, Amitai Y, Palti H, Godfrey S. Tea drinking and microcytic anemia in infants. Am J Clin Nutr 1985;41:1210-3.
Joeres R, Klinker H, Heusler H, et al. Influence of mexiletine on caffeine elimination. Pharmacol Ther 1987;33:163-9. PubMed
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.
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
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
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
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.
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. PubMed
Eskenazi B. Caffeine—filtering the facts. N Engl J Med 1999;341:1688-9. PubMed
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. PubMed
Pollock BG, Wylie M, Stack JA, et al. Inhibition of caffeine metabolism by estrogen replacement therapy in postmenopausal women. J Clin Pharmacol 1999;39:936-40. PubMed
DiPiro JT, Talbert RL, Yee GC, et al; eds. Pharmacotherapy: A pathophysiologic approach. 4th ed. Stamford, CT: Appleton & Lange, 1999.
Nurminen ML, Niittynen L, Korpela R, Vapaatalo H. Coffee, caffeine and blood pressure: a critical review. Eur J Clin Nutr 1999;53:831-9. PubMed
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. PubMed
FDA. Proposed rule: dietary supplements containing ephedrine alkaloids. Available at: www.verity.fda.gov (Accessed 25 January 2000).
Weisburger JH. Tea and health: the underlying mechanisms. Proc Soc Exp Biol Med 1999;220:271-5. PubMed
Briggs GB, Freeman RK, Yaffe SJ. Drugs in Pregnancy and Lactation. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 1998.
Hagg S, Spigset O, Mjorndal T, Dahlqvist R. Effect of caffeine on clozapine pharmacokinetics in healthy volunteers. Br J Clin Pharmacol 2000;49:59-63. PubMed
Watson JM, Jenkins EJ, Hamilton P, et al. Influence of caffeine on the frequency and perception of hypoglycemia in free-living patients with type 1 diabetes. Diabetes Care 2000;23:455-9. PubMed
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. PubMed
American Academy of Pediatrics. The transfer of drugs and other chemicals into human milk. Pediatrics 2001;108:776-89. PubMed
Sinclair CJ, Geiger JD. Caffeine use in sports. A pharmacological review. J Sports Med Phys Fitness 2000;40:71-9.
Haller CA, Benowitz NL. Adverse cardiovascular and central nervous system events associated with dietary supplements containing ephedra alkaloids. N Engl J Med 2000;343:1833-8. PubMed
Ferrini RL, Barrett-Connor E. Caffeine intake and endogenous sex steroid levels in postmenopausal women. The Rancho Bernardo Study. Am J Epidemiol 1996:144:642-4. PubMed
Bell DG, Jacobs I, Ellerington K. Effect of caffeine and ephedrine ingestion on anaerobic exercise performance. Med Sci Sports Exerc 2001;33:1399-403. PubMed
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. PubMed
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.. PubMed
McGowan JD, Altman RE, Kanto WP Jr. Neonatal withdrawal symptoms after chronic maternal ingestion of caffeine. South Med J 1988;81:1092-4.. PubMed
Massey LK. Is caffeine a risk factor for bone loss in the elderly? Am J Clin Nutr 2001;74:569-70. PubMed
Dreher HM. The effect of caffeine reduction on sleep quality and well-being in persons with HIV. J Psychosom Res 2003;54:191-8.. PubMed
Kockler DR, McCarthy MW, Lawson CL. Seizure activity and unresponsiveness after hydroxycut ingestion. Pharmacotherapy 2001;21:647-51.. PubMed
Schechter MD, Timmons GD. Objectively measured hyperactivity--II. Caffeine and amphetamine effects. J Clin Pharmacol 1985;25:276-80.. PubMed
Nix D, Zelenitsky S, Symonds W, et al. The effect of fluconazole on the pharmacokinetics of caffeine in young and elderly subjects. Clin Pharmacol Ther 1992;51:183. DOI
Infante S, Baeza ML, Calvo M, et al. Anaphylaxis due to caffeine. Allergy 2003;58:681-2. PubMed
Massey LK, Whiting SJ. Caffeine, urinary calcium, calcium metabolism and bone. J Nutr 1993;123:1611-4. PubMed
Nawrot P, Jordan S, Eastwood J, et al. Effects of caffeine on human health. Food Addit Contam 2003;20:1-30. PubMed
May DC, Jarboe CH, VanBakel AB, Williams WM. Effects of cimetidine on caffeine disposition in smokers and nonsmokers. Clin Pharmacol Ther 1982;31:656-61. PubMed
Abernethy DR, Todd EL. Impairment of caffeine clearance by chronic use of low-dose oestrogen-containing oral contraceptives. Eur J Clin Pharmacol 1985;28:425-8. PubMed
Brown NJ, Ryder D, Branch RA. A pharmacodynamic interaction between caffeine and phenylpropanolamine. Clin Pharmacol Ther 1991;50:363-71. PubMed
Sanderink GJ, Bournique B, Stevens J, et al. Involvement of human CYP1A isoenzymes in the metabolism and drug interactions of riluzole in vitro. Pharmacol Exp Ther 1997;282:1465-72. DOI
Wahllander A, Paumgartner G. Effect of ketoconazole and terbinafine on the pharmacokinetics of caffeine in healthy volunteers. Eur J Clin Pharmacol 1989;37:279-83. PubMed
Carrillo JA, Benitez J. Clinically significant pharmacokinetic interactions between dietary caffeine and medications. Clin Pharmacokinet 2000;39:127-53. PubMed
Underwood DA. Which medications should be held before a pharmacologic or exercise stress test? Cleve Clin J Med 2002;69:449-50. PubMed
Aqel RA, Zoghbi GJ, Trimm JR, et al. Effect of caffeine administered intravenously on intracoronary-administered adenosine-induced coronary hemodynamics in patients with coronary artery disease. Am J Cardiol 2004;93:343-6. PubMed
Zheng XM, Williams RC. Serum caffeine levels after 24-hour abstention: clinical implications on dipyridamole (201)Tl myocardial perfusion imaging. J Nucl Med Technol 2002;30:123-7.
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. DOI
Holmgren P, Norden-Pettersson L, Ahlner J. Caffeine fatalities--four case reports. Forensic Sci Int 2004;139:71-3. PubMed
Dews PB, O'Brien CP, Bergman J. Caffeine: behavioral effects of withdrawal and related issues. Food Chem Toxicol 2002;40:1257-61. PubMed
Benowitz NL, Osterloh J, Goldschlager N, et al. Massive catecholamine release from caffeine poisoning. JAMA 1982;248:1097-8. DOI
Leson CL, McGuigan MA, Bryson SM. Caffeine overdose in an adolescent male. J Toxicol Clin Toxicol 1988;26:407-15. PubMed
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. PubMed
Winkelmayer WC, Stampfer MJ, Willett WC, Curhan GC. Habitual caffeine intake and the risk of hypertension in women. JAMA 2005;294:2330-5. PubMed
Raaska K, Raitasuo V, Laitila J, Neuvonen PJ. Effect of caffeine-containing versus decaffeinated coffee on serum clozapine concentrations in hospitalised patients. Basic Clin Pharmacol Toxicol 2004;94:13-8. DOI
Forrest WH Jr, Bellville JW, Brown BW Jr. The interaction of caffeine with pentobarbital as a nighttime hypnotic. Anesthesiology 1972;36:37-41. PubMed
Lake CR, Rosenberg DB, Gallant S, et al. Phenylpropanolamine increases plasma caffeine levels. Clin Pharmacol Ther 1990;47:675-85. PubMed
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. PubMed
Shet, M. S., McPhaul, M., Fisher, C. W., Stallings, N. R., and Estabrook, R. W. Metabolism of the antiandrogenic drug (Flutamide) by human CYP1A2. Drug Metab Dispos. 1997;25(11):1298-1303.
Kot, M. and Daniel, W. A. Effect of diethyldithiocarbamate (DDC) and ticlopidine on CYP1A2 activity and caffeine metabolism: an in vitro comparative study with human cDNA-expressed CYP1A2 and liver microsomes. Pharmacol Rep. 2009;61(6):1216-1220. PubMed
Gasior, M., Borowicz, K., Buszewicz, G., Kleinrok, Z., and Czuczwar, S. J. Anticonvulsant activity of phenobarbital and valproate against maximal electroshock in mice during chronic treatment with caffeine and caffeine discontinuation. Epilepsia 1996;37(3 PubMed
Jankiewicz, K., Chroscinska-Krawczyk, M., Blaszczyk, B., and Czuczwar, S. J. [Caffeine and antiepileptic drugs: experimental and clinical data]. Przegl.Lek. 2007;64(11):965-967.
Chroscinska-Krawczyk, M., Jargiello-Baszak, M., Walek, M., Tylus, B., and Czuczwar, S. J. Caffeine and the anticonvulsant potency of antiepileptic drugs: experimental and clinical data. Pharmacol.Rep. 2011;63(1):12-18. PubMed
Mays, D. C., Camisa, C., Cheney, P., Pacula, C. M., Nawoot, S., and Gerber, N. Methoxsalen is a potent inhibitor of the metabolism of caffeine in humans. Clin.Pharmacol.Ther. 1987;42(6):621-626. PubMed
Wojcikowski, J. and Daniel, W. A. Perazine at therapeutic drug concentrations inhibits human cytochrome P450 isoenzyme 1A2 (CYP1A2) and caffeine metabolism--an in vitro study. Pharmacol Rep. 2009;61(5):851-858. PubMed
Daniel, W. A., Syrek, M., Rylko, Z., and Kot, M. Effects of phenothiazine neuroleptics on the rate of caffeine demethylation and hydroxylation in the rat liver. Pol.J Pharmacol 2001;53(6):615-621.
Norager, C. B., Jensen, M. B., Weimann, A., and Madsen, M. R. Metabolic effects of caffeine ingestion and physical work in 75-year old citizens. A randomized, double-blind, placebo-controlled, cross-over study. Clin Endocrinol (Oxf) 2006;65(2):223-228. PubMed
Wang, X. and Yeung, J. H. Effects of the aqueous extract from Salvia miltiorrhiza Bunge on caffeine pharmacokinetics and liver microsomal CYP1A2 activity in humans and rats. J Pharm Pharmacol 2010;62(8):1077-1083.
Kot M, Daniel WA. Caffeine as a marker substrate for testing cytochrome P450 activity in human and rat. Pharmacol Rep 2008;60:789-97.
Kjaerstad MB, Nielsen F, Nohr-Jensen L, et al. Systemic uptake of miconazole during vaginal suppository use and effect on CYP1A2 and CYP3A4 associated enzyme activities in women. Eur J Clin Pharmacol 2010;66:1189-97. PubMed
Goh BC, Reddy NJ, Dandamudi UB, et al. An evaluation of the drug interaction potential of pazopanib, an oral vascular endothelial growth factor receptor tyrosine kinase inhibitor, using a modified Cooperstown 5+1 cocktail in patients with advanced solid t
Chen Y, Kang Z, Yan J, et al. Liu wei di huang wan, a well-known traditional Chinese medicine induces CYP1A2 while suppressing CYP2A6 and N-acetyltransferase 2 acivities in man. J Ethnopharmacol 2010;132:213-8.
Suzuki S, Murayama Y, Sugiyama E, et al. Estimating pediatric doses of drugs metabolized by cytochrome P450 (CYP) isozymes, based on physiological liver development and serum protein levels. Yakugaku Zasshi 2010;130:613-20. PubMed
Chien CF, Wu YT, Lee WC, et al. Herb-drug interaction of Andrographis paniculata extract and andrographolide on the pharmacokinetics of theophylline in rats. Chem Biol Interact 2010;184:458-65. PubMed
Mills BM, Zaya MJ, Walters RR, et al. Current cytochrome P450 phenotyping methods applied to metabolic drug -drug interaction prediction in dogs. Drug Metab Dispos 2010;38:396-404. PubMed
Turpault S, Brian W, Van Horn R, et al. Pharmacokinetic assessment of a five-probe cocktail for CYPs 1A2, 2C9, 2C19, 2D6, and 3A. Br J Clin Pharmacol 2009;68:928-35. PubMed
Filimonova AA, Ziganshina LE, Ziganshin AU, Chichirov AA. On the possibility of patient phenotyping on the basis of cytochrome p-450 1A2 isoenzyme activity using caffeine as the test substrate. Eksp Klin Farmakol 2009;72:61-5.
Jenkins J, Williams D, Deng Y, et al. Eltrombopag, an oral thrombopoietin receptor agonist, has no impact on the pharmacokinetic profile of probe drugs for cytochrome P450 isoenzymes CYP3A4, CYP1A2, CYP2C9 and CYP2C19 in healthy men: a cocktail analysis.
Smits, P., Temme, L., and Thien, T. The cardiovascular interaction between caffeine and nicotine in humans. Clin Pharmacol Ther 1993;54(2):194-204. PubMed
MacKenzie, T., Comi, R., Sluss, P., Keisari, R., Manwar, S., Kim, J., Larson, R., and Baron, J. A. Metabolic and hormonal effects of caffeine: randomized, double-blind, placebo-controlled crossover trial. Metabolism 2007;56(12):1694-1698. PubMed
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. PubMed
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. PubMed
Moisey, L. L., Robinson, L. E., and Graham, T. E. Consumption of caffeinated coffee and a high carbohydrate meal affects postprandial metabolism of a subsequent oral glucose tolerance test in young, healthy males. Br.J Nutr. 2010;103(6):833-841. PubMed
Chroscinska-Krawczyk, M., Ratnaraj, N., Patsalos, P. N., and Czuczwar, S. J. Effect of caffeine on the anticonvulsant effects of oxcarbazepine, lamotrigine and tiagabine in a mouse model of generalized tonic-clonic seizures. Pharmacol Rep. 2009;61(5):819 PubMed
Simmonds, M. J., Minahan, C. L., and Sabapathy, S. Caffeine improves supramaximal cycling but not the rate of anaerobic energy release. Eur.J Appl Physiol 2010;109(2):287-295. PubMed
Buscemi, S., Verga, S., Batsis, J. A., Donatelli, M., Tranchina, M. R., Belmonte, S., Mattina, A., Re, A., and Cerasola, G. Acute effects of coffee on endothelial function in healthy subjects. Eur.J Clin Nutr. 2010;64(5):483-489. PubMed
Rigato, I., Blarasin, L., and Kette, F. Severe hypokalemia in 2 young bicycle riders due to massive caffeine intake. Clin J Sport Med. 2010;20(2):128-130. PubMed
Ernest, D., Chia, M., and Corallo, C. E. Profound hypokalaemia due to Nurofen Plus and Red Bull misuse. Crit Care Resusc. 2010;12(2):109-110. DOI
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. PubMed
Reis, J. P., Loria, C. M., Steffen, L. M., Zhou, X., van, Horn L., Siscovick, D. S., Jacobs, D. R., Jr., and Carr, J. J. Coffee, decaffeinated coffee, caffeine, and tea consumption in young adulthood and atherosclerosis later in life: the CARDIA study. A PubMed
Clausen, T. Hormonal and pharmacological modification of plasma potassium homeostasis. Fundam.Clin Pharmacol 2010;24(5):595-605. PubMed
Gronroos, N. N. and Alonso, A. Diet and risk of atrial fibrillation - epidemiologic and clinical evidence -. Circ.J 2010;74(10):2029-2038. PubMed
Perera, V., Gross, A. S., and McLachlan, A. J. Caffeine and paraxanthine HPLC assay for CYP1A2 phenotype assessment using saliva and plasma. Biomed.Chromatogr. 2010;24(10):1136-1144. PubMed
Orozco-Gregorio, H., Mota-Rojas, D., Bonilla-Jaime, H., Trujillo-Ortega, M. E., Becerril-Herrera, M., Hernandez-Gonzalez, R., and Villanueva-Garcia, D. Effects of administration of caffeine on metabolic variables in neonatal pigs with peripartum asphyxia PubMed
Izzo, A. A. and Ernst, E. Interactions between herbal medicines and prescribed drugs: an updated systematic review. Drugs 2009;69(13):1777-1798. PubMed
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 PubMed
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. PubMed
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. PubMed
Baer DJ, Novotny JA, Harris GK, Stote K, Clevidence B, Rumpler WV. Oolong tea does not improve glucose metabolism in non-diabetic adults. Eur J Clin Nutr 2011;65(1):87-93. PubMed
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;4(5):225-30.
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. PubMed
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 DOI
Voskoboinik A, Kalman JM, Kistler PM. Caffeine and arrhythmias: time to grind the data. JACC: Clin Electrophysiol. 2018;4(4):425-32. PubMed
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. PubMed
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. PubMed
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. PubMed
Alshabi AM, Alkahtani SA, Shaikh IA, Habeeb MS. Caffeine modulates pharmacokinetic and pharmacodynamic profiles of pioglitazone in diabetic rats: Impact on therapeutics. Saudi Med J 2021;42(2):151-160. PubMed
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. 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.

Brand directory

Brands that make products with Oolong Tea

37 brands in our database make a supplement containing Oolong Tea.

Obesity Research Institute 4 products OL Olympian Labs 228 products Pierce Hawthone 4 products Psychedelic Water 5 products Rapid Fire 43 products Raw Forest Foods 44 products Real Ketones 20 products Ron Teeguarden's Dragon Herbs My Cup of Tee 29 products SuperSmart 926 products Teami 5 products TerraVita Premium Collection 4,019 products Vitamin World 1,104 products XPI Xtreme Pharmaceutical Innovations 12 products

Product directory

Supplement products with Oolong Tea

80 products in our database contain Oolong Tea. Open any to see its full ingredient list and every drug interaction we check.

Pharmacist Counseling Corner

Oolong Tea: Common Questions

What is Oolong Tea used for, and does it work?

People use Oolong Tea for many reasons, but the evidence varies by use. According to the Natural Medicines database, there is at least some clinical evidence supporting Oolong Tea for Mental alertness. 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 Oolong Tea interact with prescription medications?

Yes. We list 652 medications with a known interaction with Oolong Tea, including 8 rated major. Use the checker above to see how Oolong Tea interacts with a specific drug.

How are Oolong 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 Oolong 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 Oolong 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.

What is the difference between oolong, green, and black tea?

All three come from the same plant, Camellia sinensis. The difference is how much the leaves are oxidized — green tea is barely oxidized, black tea is fully oxidized, and oolong sits in between, giving it a flavor and color partway between the two.

Does Oolong Tea really help you lose weight?

Some small studies suggest the caffeine and polyphenols in oolong may slightly boost metabolism, but the effect is small and the evidence is weak. Oolong Tea is not a reliable weight-loss treatment on its own.

How much caffeine is in Oolong Tea?

Oolong generally contains less caffeine than coffee but a moderate amount overall, often somewhere between green and black tea. The exact amount varies by the leaves and how long you steep it.

Is Oolong Tea safe to drink every day?

For most healthy adults, drinking a few cups a day is generally fine. Just keep your total caffeine in check, and talk to your doctor if you are pregnant, breastfeeding, sensitive to caffeine, or have heart or blood pressure concerns.

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

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

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Oolong Tea Drug Interactions: The Bottom Line

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The kinds of drugs Oolong Tea affects

Oolong Tea: Uses, Safety & Side Effects

Overview

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Does Oolong Tea work?

Safety & precautions

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Oolong Tea: Reported Adverse Effects

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Oolong Tea & Pregnancy

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Oolong Tea: Common Questions

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