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Dietary supplement

L-Theanine Ingredients & Drug Interactions

by XYMOGEN

L-Theanine label
See full label image
Capsule Category: Amino Acid/protein
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 16, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking L-Theanine against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Moderate

L-Theanine is a dietary supplement by XYMOGEN with 1 active ingredient. Its ingredients are commonly taken for anxiety and stress, relaxation and calm, sleep support.Based on those ingredients, 565 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Suntheanine. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against L-Theanine by XYMOGEN

Ask about any prescription or over-the-counter medication and we check it for interactions with L-Theanine by XYMOGEN — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of L-Theanine by XYMOGEN

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Aug 13, 2026

What’s inside

Full disclosure
Ingredient Transparency · database check
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 1 of its 1 active ingredient.
  • No proprietary blends here — you can verify the dose of every single component.

This product contains one active ingredient: L-theanine (supplied as Suntheanine), an amino acid derived from tea. The capsule itself includes inactive ingredients — hypromellose, water, and microcrystalline cellulose — which are standard binders and capsule materials.

Does it work?

Not established
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed
Not established

The graded evidence we hold for these ingredients covers different conditions than the ones this product is marketed for, so there's no established rating for its stated use — see Theanine's own graded uses on its monograph.

Why this rating?
  • The label markets this product for: stress reduction and relaxation without drowsiness.
  • We looked for evidence on: Stress, Generalized anxiety disorder (GAD), nervousness, tension relief.
  • The closest evidence on file: Theanine is rated "Insufficient Reliable Evidence To Rate" for Generalized anxiety disorder (GAD) (Natural Medicines).
  • Also on file: Theanine is rated "Insufficient Reliable Evidence To Rate" for Stress.

The evidence for L-theanine is mixed. It's rated possibly effective for cognitive function — meaning some evidence supports it, though more research would strengthen that claim.

For age-related cognitive decline, Alzheimer disease, generalized anxiety disorder, obsessive-compulsive disorder, and cancer, the evidence we hold isn't strong enough to make a reliable rating. If you're considering theanine for one of those uses, that's a good conversation to have with your doctor.

The evidence, ingredient by ingredient Theanine

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 1 of the 1 matched ingredient.
  • Pregnancy & breastfeeding safety ratings cover 1 of 1.
  • General safety write-ups exist for 1 of 1.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

L-Theanine is generally well tolerated in healthy adults when used short-term, but we don't have solid long-term safety data. The most common side effects are headaches, drowsiness, longer sleep duration, and increased dreams.

One pediatric case of facial tics was reported, though those tics stopped when theanine was discontinued and the child had a history of tics, so a direct link wasn't clear. There isn't enough safety data to recommend theanine during pregnancy or while breastfeeding.

If you're pregnant or nursing, talk with your doctor or pharmacist before taking this supplement.

Side effects, ingredient by ingredient Theanine

Meds to double-check

Moderate interaction found
Known Interaction Concern · database check
Moderate identified

The most serious documented interaction for these ingredients is Moderate. Check your medications for a personalized result.

Why this rating?
  • 1 of the 1 matched ingredient can interact with medications — Theanine.
  • The most serious interaction on file is rated Moderate.
  • For scale: 565 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

Before taking this product, double-check with your doctor or pharmacist if you take blood pressure medications — theanine may strengthen their effect. Also flag it if you're on sedating drugs like sleep aids or anti-anxiety medications, or if you take serotonergic drugs such as antidepressants, even though the serotonin interaction is less clear.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with no established evidence rating for its marketed use. Moderate medication interactions have been identified, and safety information is well characterized.

XYMOGEN's L-Theanine may help with focus and mental clarity, though the evidence is strongest for general cognitive function. It's not a fit if you take blood pressure medications or sedating drugs without checking first — the interactions are real and need oversight.

If you're pregnant, nursing, or take any prescription medication, have that conversation with your own doctor or pharmacist before you start.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 1 of 1 active ingredient matched to our full ingredient reviews (monographs). Based on the product label dated Dec 14, 2023.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about L-Theanine, straight from the product label.

Brand XYMOGEN
Barcode (UPC) 871149002398
Net contents 120 Vegetarian Capsule(s)
Market status On market
Date entered into DSLD Dec 14, 2023
DSLD ID 303742
Product type Amino Acid/protein
Supplement form Capsule
Dietary claims / uses Nutrient, All Other, Structure/Function
Intended target group(s) Vegan, Vegetarian, Adult (18 - 50 Years), Gluten Free, Dairy Free
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for L-Theanine by XYMOGEN, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
1 Capsule(s)
Maximum serving Sizes:
2 Capsule(s)
Servings per container
60
UPC/BARCODE
871149002398
IngredientAmount% DV
Suntheanine400 mg--

Other ingredients: Hypromellose, Water, Microcrystalline Cellulose

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
Suggested/Recommended/Usage/Directions

Directions: Take one to two capsules twice daily, or as directed by your healthcare professional.

Precautions

Consult your healthcare professional prior to use.

Individuals taking medication should discuss potential interactions with their healthcare professional.

Do not use if tamper seal is damaged.

Storage: Keep closed in a cool, dry place out of reach of children.

Formula

L-Theanine is a naturally occurring, unique amino acid found in green tea leaves. L-theanine has been found to reduce stress by promoting relaxation without drowsiness, easing nervousness due to overwork and fatigue, and reducing nervous irritability. Human studies suggest that it may also be useful in supporting concentration and in reducing negative side effects from caffeine. XYMOGEN's L-Theanine (as Suntheanine) is protected by several patents based on its positive effects.

FDA Disclaimer Statement

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

Storage

Storage: Keep closed in a cool, dry place out of reach of children.

Formulation

Does Not Contain: Wheat, gluten, corn, yeast, soy, animal and dairy products, fish, shellfish, peanuts, tree nuts, egg, sesame, ingredients derived from genetically modified organisms (GMOs), artificial colors, and artificial sweeteners.

Patented Ingredient Supports Calm and Relaxation

Vegetarian Caps

Brand IP Statement(s)

S1. Suntheanine is a registered trademark of Taiyo International, Inc. U.S. and international patents pending. U.S. Patent Nos. 6831103, 6589566, 6297280. Copyright 2023 Xymogen

Xymogen Exclusive Professional Formulas

Seals/Symbols

Vegetarian Caps ePV (ePedigree Verification)

Third-Party Verified GMP Compliant

FDA Statement of Identity

Dietary Supplement

General Statements

Scan to Learn More! This package is completely recyclable

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See for yourself

L-Theanine by XYMOGEN label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

L-Theanine label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in L-Theanine by XYMOGEN

This is the 1 active ingredient this product is made of. Select it to open its full monograph.

Serving size1 Capsule(s) Dosage formCapsule Servings per container60 Amounts shown are per serving.

Suntheanine

Interacts with
565 drugs
400 mg per serving Form: L-Theanine

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 dro...

Suntheanine monograph & interactions

Other (inactive) ingredients: Hypromellose, Water, Microcrystalline Cellulose. These complete the product’s ingredient list but are not active constituents.

Interaction report

L-Theanine by XYMOGEN Drug Interactions

Want to check YOUR meds against L-Theanine?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

 Go to the checker
565Drugs
172 Moderate 393 Minor

Ingredients driving the most interactions

Suntheanine 565

Individual Drug Interactions

The ingredients in L-Theanine interact with 565 drugs. Click any drug to see the details.

1 of the 1 ingredient in L-Theanine interact with drugs. Each result below shows which ingredient is responsible. Suntheanine

Each ingredient & the kinds of drugs it affects

For each ingredient in L-Theanine with known interactions, here are the types of medications it can affect. Open any type for the detail — or search your exact drug in the checker above.

Suntheanine3 drug types · 565 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
Suntheanine full monograph & interactions
The maker

Brand information

Manufacturer and brand details for L-Theanine, from the product label.

XYMOGEN

See all XYMOGEN products
Name
XYMOGEN Exclusive Professional Formulas
Street Address
6900 Kingspointe Pkwy.
City
Orlando
State
FL
ZipCode
32819
Phone Number
800-647-6100
Web Address
www.xymogen.com
Pharmacist Counseling Corner

L-Theanine by XYMOGEN: Common Questions

Does L-Theanine by XYMOGEN interact with any medications?
Yes. Based on its ingredients, L-Theanine has a known interaction with 565 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
L-Theanine contains a single active ingredient, and that one ingredient can interact with many different medications on its own. We check it against each medication and show the mechanism responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
Can I take L-Theanine if I'm pregnant or breastfeeding?
There isn't enough safety data to recommend it during pregnancy or breastfeeding. Talk with your doctor or pharmacist about whether it's right for you in these situations.
What side effects should I watch for?
The most common ones are headaches, drowsiness, longer sleep, and more vivid dreams. If you notice anything unusual or bothersome, stop and let your doctor know.
Does L-Theanine actually work for anxiety or brain fog?
For general cognitive function, the evidence is possibly effective — some studies support it. For anxiety disorders like GAD or OCD, we don't yet have strong enough evidence to say. Your experience may differ, and talking with your doctor about your specific goals is worth it.
Is this safe to take long-term?
Short-term use in healthy adults is generally well tolerated, but we don't have solid data on long-term safety. If you're thinking of taking it regularly, check in with your pharmacist or doctor.
What is Suntheanine?
Suntheanine is a branded form of L-theanine, an amino acid found naturally in tea. It's the active ingredient in this product.

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

Not sure if L-Theanine is safe with your meds?

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Ask a pharmacist

Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

L-Theanine label
Go deeper

The Full Monographs Behind L-Theanine’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Theanine

Interacts with 565 drugs

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...

Read the full Theanine monograph →
Sources

Sources & How We Checked

L-Theanine's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

The 6 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Theanine 6 references
  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

See these in context on the Theanine monograph →

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

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