Herb & supplement monograph

Theanine Drug Interactions, Uses, Effectiveness, Safety & More

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

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

But these pages have grown well beyond that into a full monograph — what Theanine 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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On this page

Theanine 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 Theanine drug interaction appears low for most people. None of Theanine's listed interactions are rated major, and the great majority are minor with weak or theoretical documentation.

Interactions deserving the most attention

The combination most worth watching is blood pressure medications. Animal research suggests theanine may lower blood pressure, so it could add to the effect of these drugs, though this has not been confirmed in people. There is also a theoretical chance of extra drowsiness with sedatives and other CNS depressants, since some people in one study felt sleepy after taking theanine, but this concern is unlikely to matter for most. Studies on theanine and serotonin levels conflict, yet no serotonin-related problems have actually been reported with medications that affect serotonin.

What the rest of the list means

A long list of interacting medications does not mean each combination is harmful. Most entries here are theoretical, predicted from how theanine might act on brain chemistry or blood pressure rather than from problems seen in people. In several cases, the predicted effect has not produced meaningful changes in humans.

Check your medications against Theanine

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

Interaction report

Drugs that interact with Theanine

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

2,830 drugs
AcebutololRhotral, Sectral
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Acebutolol interaction Acebutolol drug page: uses, dosage & side effects
AcetazolamideAk-Zol, Diamox
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Acetazolamide interaction Acetazolamide drug page: uses, dosage & side effects
AliskirenTekturna
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Aliskiren interaction Aliskiren drug page: uses, dosage & side effects
AmbrisentanLetairis, Volibris
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Ambrisentan interaction Ambrisentan drug page: uses, dosage & side effects
AmilorideAmilamont, Midamor
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Amiloride interaction Amiloride drug page: uses, dosage & side effects
Amiloride, HydrochlorothiazideAmil-Co, Amilzide, Moduret 25, Moduretic
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Amiloride, Hydrochlorothiazide interaction Amiloride, Hydrochlorothiazide drug page: uses, dosage & side effects
AmlodipineNorliqva
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Amlodipine interaction Amlodipine drug page: uses, dosage & side effects
Amlodipine BenzoateKaterzia
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Amlodipine Benzoate interaction Amlodipine Benzoate drug page: uses, dosage & side effects
Amlodipine BesilateIstin
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Amlodipine Besilate interaction
Amlodipine BesylateNorvasc
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Amlodipine Besylate interaction Amlodipine Besylate drug page: uses, dosage & side effects
Amlodipine Besylate, BenazeprilLotrel
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Amlodipine Besylate, Benazepril interaction
Amlodipine, CelecoxibConsensi
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Amlodipine, Celecoxib interaction
Ammonium ChlorideAmmonium Chloride
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Ammonium Chloride interaction
AprocitentanTryvio
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Aprocitentan interaction Aprocitentan drug page: uses, dosage & side effects
AtenololAtenix, Tenormin
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Atenolol interaction Atenolol drug page: uses, dosage & side effects
Atenolol, ChlortalidoneAtenixCo, Tenoret 50, Totaretic
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Atenolol, Chlortalidone interaction
Atenolol, ChlorthalidoneTenoretic
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Atenolol, Chlorthalidone interaction
AzilsartanEdarbi
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Azilsartan interaction Azilsartan drug page: uses, dosage & side effects
Azilsartan, ChlorthalidoneEdarbyclor
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Azilsartan, Chlorthalidone interaction
BenazeprilLotensin
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Benazepril interaction Benazepril drug page: uses, dosage & side effects
Benazepril, HydrochlorothiazideLotensin HCT
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Benazepril, Hydrochlorothiazide interaction
BendroflumethiazideAprinox, Naturetin, Neo-NaClex
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Bendroflumethiazide interaction
Bendroflumethiazide, NadololCorzide
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Bendroflumethiazide, Nadolol interaction
Bendroflumethiazide, Rauwolfia SerpentinaRauzide
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Bendroflumethiazide, Rauwolfia Serpentina interaction
BenzthiazideExna
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Benzthiazide interaction
BetaxololBetoptic, Kerlone
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Betaxolol interaction Betaxolol drug page: uses, dosage & side effects
BisoprololZebeta
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Bisoprolol interaction Bisoprolol drug page: uses, dosage & side effects
Bisoprolol, HydrochlorothiazideZiac
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Bisoprolol, Hydrochlorothiazide interaction
BosentanTracleer
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Bosentan interaction Bosentan drug page: uses, dosage & side effects
BumetanideBurinex
Moderate Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.

Read the full Theanine + Bumetanide interaction Bumetanide drug page: uses, dosage & side effects
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 Theanine 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 Theanine affects

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

All 3 drug categories Theanine interacts with
Antihypertensive DrugsCns DepressantsSerotonergic Drugs
Antihypertensive Drugs

Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.
Animal research shows that theanine can lower blood pressure in spontaneously hypertensive animals. Theoretically, concomitant use of theanine and antihypertensive drugs might potentiate the antihypertensive activity.

Likelihood Possible Evidence D
Cns Depressants

Theoretically, theanine might have additive sedative effects when used in conjunction with CNS depressants. However, it is unclear if this concern is clinically relevant.
Theoretically, theanine may compete with glutamate and/or increase plasma gamma-aminobutyric acid (GABA) levels, which could cause CNS depression. In one clinical study, some subjects taking oral theanine reported drowsiness.

Likelihood Unlikely Evidence D
Serotonergic Drugs

Clinical studies regarding the effects of L-theanine on serotonin levels are conflicting. Some studies suggest it can increase serotonin levels in the brain while others report that it may decrease them. Nevertheless, there have been no reports of l-theanine being a causative agent in serotonergic-related side effects or serotonin syndrome.

Likelihood Unlikely Evidence C
Monograph

Theanine: Uses, Safety & Side Effects

Medically reviewed by · Reviewed July 2026 ·
The bottom line

Theanine (usually L-theanine) is an amino acid found naturally in tea leaves that many people take to feel calmer and less stressed without strong drowsiness. Early research suggests it may help with relaxation and stress, but evidence for most uses is still limited. It appears generally well tolerated for short-term use, but check with your pharmacist or doctor before starting it.

Theanine
Part used
Naturally found in tea leaves; supplements often use a synthesized or extracted form
Common forms
Capsules, tablets, chewable tablets, powders, gummies, and tea
People commonly use it for
  • Anxiety and stress
  • Relaxation and calm
  • Sleep support
  • Focus and cognitive function

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

Safety at a glance
OverallUse caution

Generally well tolerated in healthy adults for short-term use, but long-term safety is not well studied.

PregnancyInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full pregnancy detail
BreastfeedingInsufficient reliable information

Insufficient reliable information available; avoid using.

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

Theanine is an amino acid found mostly in the leaves of the tea plant. The form used in supplements and found in tea is usually L-theanine, which is the most common natural version. It gives tea part of its flavor and is thought to be one reason tea can feel calming even though it also contains caffeine.

People take theanine as a supplement to help with stress, relaxation, sleep, and focus. It is sold on its own and is also a popular ingredient in products marketed for calm or mental performance, where it is sometimes combined with caffeine.

How it works

Theanine is thought to affect chemical messengers in the brain. Researchers believe it may influence GABA, serotonin, and dopamine, which are involved in mood, calmness, and alertness. It may also change certain brain wave patterns linked to a relaxed-but-alert state.

It is important to know that much of this comes from laboratory and animal research, or small human studies. The exact way theanine works in people is not fully understood, and the proposed mechanisms do not guarantee a clear benefit.

Effectiveness

Does Theanine work?

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

Evidence overview · 18 uses evaluated
1 Possibly effective 17 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.
Possibly Effective Cognitive function
Rating & evidence shown verbatim from Natural Medicines

Oral L-theanine may improve some aspects of cognitive function. It is unclear if using L-theanine in conjunction with caffeine can enhance the effects of either ingredient.

Also studied for 17 conditions — evidence insufficient to rate
Insufficient Reliable Evidence To Rate Age-related cognitive decline
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral L-theanine, taken continuously or as a single dose, improves cognition in older adults.

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

Although there is interest in using oral theanine for Alzheimer disease, there is insufficient reliable information about the clinical effects of theanine for this condition.

Insufficient Reliable Evidence To Rate Attention deficit-hyperactivity disorder (ADHD)
Rating & evidence shown verbatim from Natural Medicines

Oral L-theanine seems to improve some aspects of ADHD, including cognition and sleep.

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

Although there is interest in using oral theanine for cancer, there is insufficient reliable information about the clinical effects of theanine for this condition.

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

Oral L-theanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear.

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

Oral L-theanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear.

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

It is unclear if oral L-theanine is beneficial in patients with depression.

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

Oral L-theanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear.

Insufficient Reliable Evidence To Rate Generalized anxiety disorder (GAD)
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral L-theanine is beneficial for reducing anxiety in people with GAD.

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

Although there is interest in using oral theanine for hypertension, there is insufficient reliable information about the clinical effects of theanine for this condition.

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

Oral L-theanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear.

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

It is unclear if oral L-theanine is beneficial for insomnia.

Insufficient Reliable Evidence To Rate Obsessive-compulsive disorder (OCD)
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral L-theanine is beneficial for OCD.

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

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

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

It is unclear if oral L-theanine is beneficial in patients with schizophrenia; the available evidence is limited and conflicting.

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

It is unclear if oral L-theanine is beneficial in patients with stress.

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

It is unclear if oral L-theanine is beneficial in children with Tourette syndrome.

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

Theanine appears to be generally well tolerated in healthy adults when used short term. However, long-term safety has not been well studied, and supplement quality can vary between brands.

People who are sensitive to sedating effects, who have low blood pressure, or who take medicines that cause drowsiness should be cautious and speak with a pharmacist first. Because it may promote relaxation or sleepiness in some people, use care when driving or doing tasks that need full alertness until you know how it affects you.

For pregnancy and breastfeeding, there is not enough reliable safety information about theanine supplements, so it is best to avoid them during these times. Drinking ordinary tea is different from taking concentrated supplements, but tea also contains caffeine, so discuss your intake with your doctor.

Side effects

Theanine usually causes few side effects. When they happen, they may include headache, dizziness, drowsiness, or stomach upset. Some products that combine theanine with caffeine may cause caffeine-related effects like jitteriness or trouble sleeping.

Serious reactions appear to be rare, but allergic reactions are always possible with any supplement. Stop using it and seek medical care if you notice rash, swelling, or trouble breathing.

Theanine: Reported Adverse Effects

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

Reports by condition
Insomnia Neurologic/CNS

Orally, L-theanine may cause headaches. Patients have also reported drowsiness, increased duration of sleep, and increased dream activity after oral L-theanine use.

A case of subtle facial tic starting within 4 days of taking L-theanine 400 mg daily has been reported for a pediatric patient. Although the tics reportedly ceased once theanine was discontinued, the child had exhibited tics in the past. Therefore, the adverse effect was not thought to be related to L-theanine.

  1. Haskell, C. F., Kennedy, D. O., Milne, A. L., Wesnes, K. A., and Scholey, A. B. The effects of L-theanine, caffeine and their combination on cognition and mood. Biol.Psychol. 2008;77(2):113-122.
  2. Hidese S, Ota M, Wakabayashi C, et al. Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study. Acta Neuropsychiatr 2017;29(2):72-9.
  3. Lyon MR, Kapoor MP, Juneja LR. The effects of L-theanine (Suntheanine®) on objective sleep quality in boys with attention deficit hyperactivity disorder (ADHD): a randomized, double-blind, placebo-controlled clinical trial. Altern Med Rev. 2011;16(4):348-
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 theanine, and the right amount can vary by product and reason for use. The best approach is to follow the directions on the product label and not exceed them.

Because supplements are not tightly regulated, doses and quality differ between brands. Check with your pharmacist or doctor before starting theanine, especially if you take other medicines or have a health condition.

Pregnancy & Breastfeeding

Theanine & Pregnancy

Insufficient reliable information

Insufficient reliable information available; avoid using.

Theanine & Breastfeeding

Insufficient reliable information

Insufficient reliable information available; avoid using.

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 6 references that drive our Theanine 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. Yokogoshi H, Kobayashi M. Hypotensive effect of gamma-glutamylethylamide in spontaneously hypertensive rats. Life Sci 1998;62:1065-8.
  2. Haskell, C. F., Kennedy, D. O., Milne, A. L., Wesnes, K. A., and Scholey, A. B. The effects of L-theanine, caffeine and their combination on cognition and mood. Biol.Psychol. 2008;77(2):113-122. PubMed
  3. Yokogoshi, H., Kato, Y., Sagesaka, Y. M., Takihara-Matsuura, T., Kakuda, T., and Takeuchi, N. Reduction effect of theanine on blood pressure and brain 5-hydroxyindoles in spontaneously hypertensive rats. Biosci.Biotechnol.Biochem. 1995;59(4):615-618. PubMed
  4. Lyon MR, Kapoor MP, Juneja LR. The effects of L-theanine (Suntheanine®) on objective sleep quality in boys with attention deficit hyperactivity disorder (ADHD): a randomized, double-blind, placebo-controlled clinical trial. Altern Med Rev. 2011;16(4):348-
  5. Hidese S, Ota M, Wakabayashi C, et al. Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study. Acta Neuropsychiatr 2017;29(2):72-9.
  6. Tsuchiya T, Honda H, Oikawa M, et al. Oral administration of the amino acids cystine and theanine attenuates the adverse events of S-1 adjuvant chemotherapy in gastrointestinal cancer patients. Int J Clin Oncol 2016;21(6):1085-90. 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 Theanine

922 brands in our database make a supplement containing Theanine.

Product directory

Supplement products with Theanine

3,310 products in our database contain Theanine. Open any to see its full ingredient list and every drug interaction we check.

#NoFilter Sleep by N by Nutrilite Gummy Or Jelly 60 Gummy(ies) View ingredients & interactions +Elevate by Avantera Capsule 60 Capsule(s) View ingredients & interactions +Stress Relief Stress Relief Complex by Shaklee Other (e.g. Tea Bag) 30 Caplet(s) View ingredients & interactions 01-02-Go by Pure Nootropics Capsule 90 Vegetarian Capsule(s) View ingredients & interactions 10 Berry by LXR Biotech Liquid 12 {Bottle(s)} View ingredients & interactions 10 Berry by LXR Biotech Liquid 1.93 fl. Oz. · 57 mL View ingredients & interactions 10 Grape by LXR Biotech Liquid 12 {Bottle(s)} View ingredients & interactions 10 Grape by LXR Biotech Liquid View ingredients & interactions 100% Pure L-Theanine 200 Milligrams by NutraBio Capsule 90 Cap(s) View ingredients & interactions 10x Pure-Gold Sleep All Night by CTFO Changing The Future Outcome Capsule 60 Capsule(s) View ingredients & interactions 200 mg of Zen by Allergy Research Group Capsule 60 Vegetarian Capsule(s) View ingredients & interactions 200 mg of Zen by Allergy Research Group Capsule 60 Vegetarian Capsule(s) View ingredients & interactions 200 mg of Zen by Allergy Research Group Capsule 120 Vegetarian Capsule(s) View ingredients & interactions 200 mg of Zen by Allergy Research Group Capsule 120 Vegetarian Capsule(s) View ingredients & interactions 24K by Reliv Powder 10.6 Ounce(s) View ingredients & interactions 24K by Reliv Liquid 30 fl. Oz. · 1 pt. · 14 fl. Oz. · 887 mL View ingredients & interactions 24K Mixed Berry Flavor by Reliv Powder 10.6 Ounce(s) View ingredients & interactions 3 a.m. Melatonin Fast Dissolve Lavender Vanilla by Natrol Tablet Or Pill 24 Tablet(s) View ingredients & interactions 3 a.m. Melatonin Fast Dissolve Lavender Vanilla by Natrol Tablet Or Pill 60 Tablet(s) View ingredients & interactions 3 a.m. Melatonin Fast Dissolve Lavender Vanilla by Natrol Tablet Or Pill 30 Tablet(s) View ingredients & interactions 3 a.m. Melatonin Fast Dissolve Lavender Vanilla by Natrol Tablet Or Pill 60 Tablet(s) View ingredients & interactions 3 a.m. Melatonin Lavender Vanilla by Natrol Tablet Or Pill 60 Tablet(s) View ingredients & interactions 3-in-1 Apigenin Magnesium Theanine Complex by eleva NUTRITION Capsule 120 Capsule(s) View ingredients & interactions 3-in-1 Magtein Apigenin Theanine Complex by eleva NUTRITION Capsule 120 Capsule(s) View ingredients & interactions
Pharmacist Counseling Corner

Theanine: Common Questions

What is Theanine used for, and does it work?
People use Theanine for many reasons, but the evidence varies by use. According to the Natural Medicines database, there is at least some clinical evidence supporting Theanine for Cognitive function. 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 Theanine interact with prescription medications?
Yes. We list 565 medications with a known interaction with Theanine. Use the checker above to see how Theanine interacts with a specific drug.
How are Theanine 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 Theanine 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 Theanine 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 Theanine used for?
People most often take Theanine to feel calmer and less stressed, and sometimes for sleep or focus. The evidence is still limited, so it is not proven to treat any medical condition.
Does Theanine make you sleepy?
Theanine is more often described as promoting a relaxed, calm feeling rather than strong drowsiness, but some people may feel sleepy. Use caution with driving or focus-heavy tasks until you know how it affects you.
Is Theanine safe to take every day?
It appears generally well tolerated for short-term use in healthy adults, but long-term daily safety has not been well studied. Talk with your pharmacist or doctor before using it regularly.
Can I take Theanine if I'm pregnant or breastfeeding?
There isn't enough reliable safety data, so it's best to avoid Theanine supplements during pregnancy and breastfeeding unless your doctor advises otherwise.

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

Keep exploring

Products that contain Theanine

A rotating sample of real supplements in our database that list Theanine — open any to see its full ingredients and every drug interaction we check.

See all 3,310 products with Theanine →
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