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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 30, 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 L-Theanine. 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, an amino acid naturally found in tea that works on brain chemistry to support calm focus. The capsule also contains inactive ingredients — vegetable cellulose, magnesium stearate (a flow agent), and the capsule shell itself — which are common excipients that help deliver the active ingredient.

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: Calming and relaxation.
  • We looked for evidence on: Generalized anxiety disorder (GAD), Stress, Anxiety, Sleep quality.
  • 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.

L-theanine is rated possibly effective for cognitive function — meaning there's some evidence it may help with focus and mental performance. For other uses listed on the label — age-related cognitive decline, Alzheimer disease, generalized anxiety, and OCD — the evidence isn't established well enough in the data we hold to rate it one way or the other.

If cognitive support is what you're after, the strongest evidence backs that use.

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 for short-term use, but how safe it is over the long term hasn't been well studied. The most common side effects in people who've taken it are headaches, drowsiness, longer sleep, and more vivid dreams.

There isn't enough safety data to recommend it during pregnancy or while breastfeeding — talk with your doctor or pharmacist about whether it's right for you in either situation.

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 you start, check with your doctor or pharmacist if you take blood pressure medications — theanine can lower pressure and might intensify their effect. Also check if you're on sedatives, sleeping pills, opioids, or other central nervous system depressants, or any drugs that affect serotonin levels, because minor interactions are documented.

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.

L-theanine may help with focus and mental clarity, and it's generally well tolerated short-term. If you take blood pressure medication, sedatives, or drugs affecting serotonin, you'll want to check with your doctor or pharmacist before adding it — the interaction potential is real.

Long-term safety data is thin, and pregnancy or breastfeeding are situations to discuss with your own healthcare provider first.

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 Mar 23, 2012.

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
Net contents 120 Vegetable Capsule(s)
Market status On market
Date entered into DSLD Mar 23, 2012
DSLD ID 6137
Product type Amino Acid/protein
Supplement form Capsule
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Vegetarian, Adult (18 - 50 Years), Gluten 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
120
IngredientAmount% DV
L-Theanine200 mg--

Other ingredients: Vegetable Capsule, Cellulose, Magnesium Stearate

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.
FDA Statement of Identity

Dietary Supplement

Suggested/Recommended/Usage/Directions

Directions: Take 1-2 capsules daily or as directed by your healthcare practitioner.

Precautions

CAUTION: Keep out of reach of children.

• Pharmaceutical Grade • Professional Use Only

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 tightly closed in a cool, dry place.

General Statements

Patented Ingredient Supports Calming and Relaxation

This package is completely recyclable (recycle)

EXCLUSIVE PROFESSIONAL FORMULAS

Brand IP Statement(s)

XYMOGEN 2009

All XYMOGEN(R) Formulas Meet or Exceed cGMP Quality Standards.

L-Theanine is a naturally-occurring, unique amino acid found in green tea leaves. XYMOGEN(R)’s L-Theanine, SunTheanin(R), is protected by over 40 patents. L-Theanine may promote a sense of physical relaxation, mental alertness and mental well-being by reducing feelings of stress and anxiety. Research with human subjects suggests L-Theanine may also be useful to improve learning performance, promote concentration and reduce negative side effects of caffeine.*

Formulation

DOES NOT CONTAIN: Wheat, gluten, yeast, dairy products, artificial colors, sweeteners or preservatives.

Seals/Symbols

VEGETABLE CAPSULES

General

REV. 061909

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

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 container120 Amounts shown are per serving.

L-Theanine

Interacts with
565 drugs
200 mg per serving

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...

L-Theanine monograph & interactions

Other (inactive) ingredients: Vegetable Capsule, Cellulose, Magnesium Stearate. 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

L-Theanine 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. L-Theanine

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.

L-Theanine3 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
L-Theanine 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
725 S. Kirkman Rd.
City
Orlando
State
FL
ZipCode
32811
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 on L-theanine in pregnancy or lactation to know if it's safe. Talk with your doctor or pharmacist about your situation — they can help you weigh any potential benefit against what we don't yet know.
What side effects might I notice?
The most common ones are headaches, drowsiness, and longer or more vivid dreams. Most people tolerate it well, especially short-term, but if you notice anything bothersome, let your healthcare provider know.
Will L-theanine help my anxiety or OCD?
The evidence for anxiety and OCD isn't established enough in the data we hold to say. What we do know is it's possibly effective for cognitive function and focus. If you're considering it for anxiety or OCD, that's a conversation for your doctor.
How long can I safely take this?
L-theanine is generally well tolerated for short-term use in healthy adults, but long-term safety hasn't been well studied. If you're thinking of taking it regularly for months or longer, check in with your doctor or pharmacist first.

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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