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Dietary supplement

L-Theanine 400 mg Ingredients & Drug Interactions

by OL Olympian Labs, Inc.

L-Theanine 400 mg label
See full label image
Capsule Category: Non-nutrient/non-botanical
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 400 mg 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 400 mg is a dietary supplement by OL Olympian Labs, Inc. 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 400 mg by OL Olympian Labs, Inc.

Ask about any prescription or over-the-counter medication and we check it for interactions with L-Theanine 400 mg by OL Olympian Labs, Inc. — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of L-Theanine 400 mg by OL Olympian Labs, Inc.

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 a single active ingredient: L-theanine, an amino acid naturally found in tea that may help support cognitive function and calm. The capsule itself is vegetarian, and the remaining ingredients (rice flour, microcrystalline cellulose, silicon dioxide, and ascorbyl palmitate) are inactive fillers and preservatives that make up the capsule and help keep the product stable.

Does it work?

Moderate evidence
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
Moderate

Some clinical evidence supports this product's ingredients for its stated purpose, but it isn't conclusive.

Why this rating?
  • The label markets this product for: stress, anxiety, and mental focus support.
  • We looked for evidence on: Generalized anxiety disorder (GAD), Stress, Cognitive function, Attention deficit-hyperactivity disorder (ADHD), relaxation, calm — and 1 related terms.
  • The strongest evidence on file: Theanine is rated "Possibly Effective" for Cognitive function (Natural Medicines).
  • Also on file: Theanine is rated "Insufficient Reliable Evidence To Rate" for Generalized anxiety disorder (GAD), Attention deficit-hyperactivity disorder (ADHD), Stress.

The evidence shows L-theanine is possibly effective for supporting cognitive function — that's the one use with meaningful research behind it. For age-related cognitive decline, Alzheimer's disease, generalized anxiety, obsessive-compulsive disorder, and cancer, the evidence isn't established enough in the data we hold to rate it either way.

If you're considering theanine for one of those other purposes, talk it over with your doctor or pharmacist about what the broader research landscape looks like.

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 long-term hasn't been well studied. The most common side effects are headaches, drowsiness, longer sleep, and more vivid dreams.

One pediatric case of a facial tic was reported after starting 400 mg daily, but it went away when the supplement was stopped, and the child had a history of tics, so the connection wasn't clear. There isn't enough safety data to know whether theanine is safe in pregnancy or while breastfeeding.

If you're pregnant, planning to become pregnant, or nursing, talk with your doctor or pharmacist before taking it — that's an individual decision based on your whole health picture.

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 take this product, double-check with your doctor or pharmacist if you take blood pressure medications — theanine may enhance their effect and lower your blood pressure too much. Also flag any sedating drugs (sleep aids, anxiety meds, some pain relievers) and any antidepressants or other serotonergic drugs, even though clinical problems haven't been reported with the latter.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with some supporting evidence for its stated purpose. Moderate medication interactions have been identified, and safety information is well characterized.

L-Theanine might be worth considering if you're looking for cognitive support and you don't take blood pressure medications, sedatives, or serotonergic drugs. If you do take any of those, check your specific medications first with your doctor or pharmacist.

Keep in mind the long-term safety picture isn't as clear as the short-term one, and if you're pregnant or breastfeeding, you'll want personalized advice before starting.

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 23, 2016.

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 400 mg, straight from the product label.

Brand OL Olympian Labs, Inc.
Barcode (UPC) 710013032317
Net contents 60 Vegetarian Capsule(s)
Market status On market
Date entered into DSLD Dec 23, 2016
DSLD ID 67068
Product type Non-nutrient/non-botanical
Supplement form Capsule
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Vegan, Vegetarian, Adult (18 - 50 Years), No Allergies, 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 400 mg by OL Olympian Labs, Inc., 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:
2 Capsule(s)
Maximum serving Sizes:
2 Capsule(s)
Servings per container
30
UPC/BARCODE
710013032317
IngredientAmount% DV
L-Theanine400 mg--

Other ingredients: Vegetarian Capsule, Rice Flour, Microcrystalline Cellulose, Silicon Dioxide, Ascorbyl Palmitate

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.
Formulation

Non-GMO

Vegan

Gluten free

No: Milk, Eggs, Fish, Crustaceans Shellfish, Tree Nuts, Peanuts, Wheat, or Soybeans.

Allergen free

General Statements

Helps reduce stress & anxiety

Mental focus support

Relax without feeling drowsy

30 servings

Made in USA

We do not use ingredients that were produced using modern biotechnology

Pharmaceutical grade

Olympian Labs, Inc. products are made with the highest quality ingredients and manufactured according to current Good Manufacturing Practices (cGMP).

Formula

Allergen free

L-Theanine 400 mg per serving

General

Rev 07-18-16

Suggested/Recommended/Usage/Directions

Suggested Use: As a dietary supplement, take two (2) capsules daily on an empty stomach, or as directed by a healthcare professional.

FDA Statement of Identity

Dietary Supplement

Precautions

Discontinue use if allergic reaction occurs.

Keep out of reach of children.

Caution: If you are pregnant or nursing, have a medical condition, or are taking medication, consult your healthcare professional before using this or any other nutritional supplement.

Storage

Store in a cool, dry place.

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.

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

See for yourself

L-Theanine 400 mg by OL Olympian Labs, Inc. label

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

L-Theanine 400 mg 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 400 mg by OL Olympian Labs, Inc.

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

Serving size2 Capsule(s) Dosage formCapsule Servings per container30 Amounts shown are per serving.

L-Theanine

Interacts with
565 drugs
400 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: Vegetarian Capsule, Rice Flour, Microcrystalline Cellulose, Silicon Dioxide, Ascorbyl Palmitate. These complete the product’s ingredient list but are not active constituents.

Interaction report

L-Theanine 400 mg by OL Olympian Labs, Inc. Drug Interactions

Want to check YOUR meds against L-Theanine 400 mg?

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 400 mg interact with 565 drugs. Click any drug to see the details.

1 of the 1 ingredient in L-Theanine 400 mg 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 400 mg 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 400 mg, from the product label.

OL Olympian Labs, Inc.

Name
Olympian Labs, Inc.
City
Phoenix
State
AZ
ZipCode
85027
Phone Number
1.800.473.5883
Web Address
www.olympianlabs.com
Pharmacist Counseling Corner

L-Theanine 400 mg by OL Olympian Labs, Inc.: Common Questions

Does L-Theanine 400 mg by OL Olympian Labs, Inc. interact with any medications?
Yes. Based on its ingredients, L-Theanine 400 mg 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 400 mg 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.
What is L-theanine and what does it do?
L-theanine is an amino acid found naturally in tea. In this product, it's studied mainly for its ability to support cognitive function — that's the one area where there's meaningful evidence. It may also have a calming effect, though the evidence for anxiety and other uses isn't established yet.
Can I take this if I'm pregnant or breastfeeding?
There isn't enough safety data to know whether theanine is safe during pregnancy or while breastfeeding. The safety data advises against taking it in both situations. Talk with your doctor or pharmacist about your specific situation — they can help you weigh what you need against the unknowns.
What side effects might I notice?
The most common ones are headaches, drowsiness, sleeping longer than usual, and more vivid dreams. These are generally mild, but if you're sensitive to sedating effects or have a history of tics, mention it to your doctor or pharmacist before starting.
Is this safe to take long-term?
Theanine is generally well tolerated in healthy adults for short-term use, but we don't have good data on long-term safety. If you're thinking of taking it regularly for months, talk with your doctor or pharmacist about what that means for you specifically.
Does it work for anxiety or sleep?
The evidence for generalized anxiety and sleep isn't established in the data we hold — meaning we don't have enough strong research to say yes or no. For cognitive function, the evidence is stronger (possibly effective). If you're considering theanine for anxiety or sleep, check with your doctor or pharmacist about what the research shows.
Will this help my memory or brain fog?
L-theanine is possibly effective for cognitive function, so it may help with mental clarity. It's not shown to help with age-related memory decline or Alzheimer's disease based on the data we have. Your doctor or pharmacist can help you figure out whether it might fit your specific needs.

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

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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 400 mg label
Go deeper

The Full Monographs Behind L-Theanine 400 mg’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 400 mg'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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