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Dietary supplement

L-Theanine (500 mg) Ingredients & Drug Interactions

by BulkSupplements.com

L-Theanine (500 mg) label
See full label image
Capsule Category: Non-nutrient/non-botanical
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 (500 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 (500 mg) is a dietary supplement by BulkSupplements.com 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 (500 mg) by BulkSupplements.com

Ask about any prescription or over-the-counter medication and we check it for interactions with L-Theanine (500 mg) by BulkSupplements.com — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of L-Theanine (500 mg) by BulkSupplements.com

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 Oct 1, 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: 500 mg of L-theanine per capsule. Theanine is an amino acid found naturally in tea leaves; it's thought to support relaxation and mental clarity without causing drowsiness on its own.

The capsule itself is made of bovine gelatin, an inactive ingredient that holds the powder together.

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

This product doesn't appear to be marketed for a specific use, so we graded Theanine's overall clinical evidence instead.

Moderate

Some clinical evidence supports Theanine for:

Why this rating?
  • We looked at the product name, claims, and label statements and couldn't find a stated purpose to grade.
  • Since the label doesn't commit to one use, we graded the ingredient's overall clinical evidence instead.
  • On file: Cognitive function — rated "Possibly Effective" (Natural Medicines).

L-theanine shows possibly effective evidence for supporting cognitive function — the clearest indication we have from the data. For age-related cognitive decline, Alzheimer disease, generalized anxiety disorder, obsessive-compulsive disorder, and cancer, the evidence is insufficient to rate whether it works.

That doesn't mean it doesn't help with those conditions, just that we don't have strong enough data yet to say either way.

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, though long-term safety hasn't been thoroughly studied. Some people report headaches, drowsiness, longer sleep, or more vivid dreams after taking it.

There isn't enough safety data to recommend this supplement during pregnancy or breastfeeding — talk with your doctor or pharmacist about whether it's right for you if you're pregnant, planning to become pregnant, or nursing.

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.

Double-check this product with your doctor or pharmacist before taking it if you're on blood pressure medication — theanine may make it work harder. Also confirm it's okay if you take CNS depressants (sleeping pills, anxiety medications, benzodiazepines) or serotonergic antidepressants, even though serious problems aren't documented.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with some supporting evidence behind its ingredients' uses. Moderate medication interactions have been identified, and safety information is well characterized.

L-theanine may help with everyday focus and mental clarity, but your main concern is whether it will lower your blood pressure too much if you're on blood pressure medication. If you take any blood pressure drugs, sedatives, or serotonergic antidepressants, check with your own doctor or pharmacist before starting.

For most other people without those medications, it's generally well tolerated short-term.

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 May 23, 2024.

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 (500 mg), straight from the product label.

Brand BulkSupplements.com
Barcode (UPC) X000OD1EHR
Net contents 100 Gelatin Capsule(s)
Market status On market
Date entered into DSLD May 23, 2024
DSLD ID 312277
Product type Non-nutrient/non-botanical
Supplement form Capsule
Dietary claims / uses All Other, Structure/Function
Intended target group(s) 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 (500 mg) by BulkSupplements.com, 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:
1 Capsule(s)
Servings per container
100
UPC/BARCODE
X000OD1EHR
IngredientAmount% DV
L-Theanine500 mg--

Other ingredients: Bovine Gelatin

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.
Brand IP Statement(s)

BulkSupplements.com Clean & Pure Bulk Supplements

Formula

L-Theanine (500 mg per serving)

Formulation

Free of: Added sugar, soy, dairy, yeast, gluten, additives

Suggested/Recommended/Usage/Directions

Suggested use: As a dietary supplement, take 1 capsule once or twice daily, or as directed by a physician.

Storage

Store in a dry, cool place

FDA Disclaimer Statement

Warning: This product is not intended to diagnose, treat, cure, or prevent any disease.

Precautions

Always consult a physician before taking any dietary supplement.

Keep out of reach of children.

General Statements

New

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

See for yourself

L-Theanine (500 mg) by BulkSupplements.com label

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

L-Theanine (500 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 (500 mg) by BulkSupplements.com

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 container100 Amounts shown are per serving.

L-Theanine

Interacts with
565 drugs
500 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: Bovine Gelatin. These complete the product’s ingredient list but are not active constituents.

Interaction report

L-Theanine (500 mg) by BulkSupplements.com Drug Interactions

Want to check YOUR meds against L-Theanine (500 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 (500 mg) interact with 565 drugs. Click any drug to see the details.

1 of the 1 ingredient in L-Theanine (500 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 (500 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 (500 mg), from the product label.

BulkSupplements.com

See all BulkSupplements.com products
Name
BulkSupplements.com
Street Address
7511 Eastgate Rd
City
Henderson
State
NV
ZipCode
89011
Web Address
BulkSupplements.com
Pharmacist Counseling Corner

L-Theanine (500 mg) by BulkSupplements.com: Common Questions

Does L-Theanine (500 mg) by BulkSupplements.com interact with any medications?
Yes. Based on its ingredients, L-Theanine (500 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 (500 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.
Will L-theanine make me drowsy?
Not necessarily. Theanine is often used for calm focus without sedation, but some people do report drowsiness, longer sleep, or more vivid dreams after taking it. Start with a smaller dose if you're concerned, and see how you feel.
Can I take this while pregnant or breastfeeding?
The safety data just isn't there yet. The facts advise against it during pregnancy and breastfeeding because we don't know enough. Talk with your doctor or pharmacist about your specific situation — they can weigh the risks and benefits for you.
How long can I take L-theanine?
It's generally well tolerated for short-term use in healthy adults, but long-term safety hasn't been well studied. If you're planning to take it regularly for months, check in with your doctor or pharmacist about what's safe for you.
What is L-theanine and where does it come from?
L-theanine is an amino acid found naturally in tea leaves. It's thought to promote relaxation and mental focus without the jitters you might get from caffeine alone.
Will this help with anxiety?
The evidence for generalized anxiety disorder is insufficient to rate — meaning we don't have strong enough data yet to say whether it works for anxiety. Some people find it calming, but the science isn't settled.

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

Not sure if L-Theanine (500 mg) is safe with your meds?

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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 (500 mg) label
Go deeper

The Full Monographs Behind L-Theanine (500 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 (500 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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