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Dietary supplement

L-Theanine 200 mg Ingredients & Drug Interactions

by GNC

L-Theanine 200 mg label
See full label image
Capsule Category: Non-nutrient/non-botanical
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 9, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking L-Theanine 200 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 200 mg is a dietary supplement by GNC 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 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 200 mg by GNC

Ask about any prescription or over-the-counter medication and we check it for interactions with L-Theanine 200 mg by GNC — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of L-Theanine 200 mg by GNC

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: Suntheanine L-Theanine 200 mg per capsule. L-Theanine is an amino acid that may promote relaxation and support focus without drowsiness.

The capsule also holds inactive ingredients — microcrystalline cellulose (a filler), gelatin (the capsule shell), magnesium stearate (a flow agent), and silicon dioxide (an anti-caking agent).

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: helps promote a sense of relaxation.
  • We looked for evidence on: Stress, Generalized anxiety disorder (GAD), anxiety, calmness, tension relief.
  • The closest evidence on file: Theanine is rated "Insufficient Reliable Evidence To Rate" for Anxiety (Natural Medicines).
  • Also on file: Theanine is rated "Insufficient Reliable Evidence To Rate" for Generalized anxiety disorder (GAD), Stress.

The evidence for L-Theanine is mixed and incomplete. It's rated Possibly Effective for cognitive function — meaning some evidence supports it, but more research is needed.

For age-related cognitive decline, Alzheimer disease, generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), and cancer, we don't have enough reliable evidence to rate whether it works. If you're considering this for one of those conditions, talk with your doctor about whether the current evidence supports a trial.

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 its long-term safety hasn't been well studied. The most common side effects are headaches, drowsiness, increased sleep duration, and vivid dreams.

A rare case of facial tics was reported in a child taking a higher dose, but the tics stopped when the supplement was discontinued — and the child had a history of tics, so causation wasn't clear. There isn't enough safety data in pregnancy or while breastfeeding.

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

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 pharmacist if you take antihypertensive drugs (blood pressure medications) — theanine may lower pressure further, which is the most serious documented concern. Also flag any CNS depressants (sedatives, sleep aids, or alcohol) or serotonergic drugs (antidepressants and related medications) before you start.

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 calm, though the best evidence is for cognitive function. It's generally well tolerated short-term, but if you take blood pressure or anxiety medications, CNS depressants, or antidepressants, you'll want to check your specific drugs with your doctor or pharmacist before starting — theanine can potentiate some of these, especially blood pressure meds.

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 Jan 22, 2021.

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 200 mg, straight from the product label.

Brand GNC
Barcode (UPC) 048107211264
Net contents 60 Capsule(s)
Market status On market
Date entered into DSLD Jan 22, 2021
DSLD ID 243017
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, Sugar 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 200 mg by GNC, 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
60
UPC/BARCODE
048107211264
IngredientAmount% DV
Suntheanine L-Theanine200 mg--

Other ingredients: Microcrystalline Cellulose, Gelatin, Magnesium Stearate, Silicon Dioxide

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.
Precautions

Keep out of reach of children.

Storage

Store in a cool, dry place.

Formulation

Helps promote a sense of relaxation

Conforms to USP <2091> for weight. Meets USP <2040> disintegration.

No sugar, no artificial colors, no artificial flavors, no wheat, gluten free, no corn, no soy, no dairy.

General Statements

60-day supply

FDA Statement of Identity

Dietary Supplement

Suggested/Recommended/Usage/Directions

Directions: As a dietary supplement, take one capsule daily.

Brand IP Statement(s)

Suntheanine is a registered trademark of Taiyo International, Inc.

FDA Disclaimer Statement

This statement has 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 200 mg by GNC label

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

L-Theanine 200 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 200 mg by GNC

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 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...

Suntheanine L-Theanine monograph & interactions

Other (inactive) ingredients: Microcrystalline Cellulose, Gelatin, Magnesium Stearate, Silicon Dioxide. These complete the product’s ingredient list but are not active constituents.

Interaction report

L-Theanine 200 mg by GNC Drug Interactions

Want to check YOUR meds against L-Theanine 200 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

Suntheanine L-Theanine 565

Individual Drug Interactions

The ingredients in L-Theanine 200 mg interact with 565 drugs. Click any drug to see the details.

1 of the 1 ingredient in L-Theanine 200 mg interact with drugs. Each result below shows which ingredient is responsible. Suntheanine L-Theanine

Each ingredient & the kinds of drugs it affects

For each ingredient in L-Theanine 200 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.

Suntheanine 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
Suntheanine L-Theanine full monograph & interactions
The maker

Brand information

Manufacturer and brand details for L-Theanine 200 mg, from the product label.

GNC

See all GNC products
Name
General Nutrition Corporation
City
Pittsburgh
State
PA
ZipCode
15222
Phone Number
1-888-462-2548
Web Address
gnc.com
Pharmacist Counseling Corner

L-Theanine 200 mg by GNC: Common Questions

Does L-Theanine 200 mg by GNC interact with any medications?
Yes. Based on its ingredients, L-Theanine 200 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 200 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 that may promote relaxation and support focus. The evidence shows it's possibly effective for cognitive function, but we don't have enough reliable data yet to say whether it helps with anxiety disorders, age-related memory loss, or Alzheimer disease.
Is L-Theanine safe to take long-term?
It's generally well tolerated in healthy adults for short-term use, but long-term safety hasn't been well studied. If you're planning to take it regularly for months or longer, it's worth discussing with your doctor or pharmacist.
Can I take L-Theanine if I'm pregnant or breastfeeding?
There isn't enough safety data to know whether it's safe during pregnancy or while breastfeeding. Talk with your doctor or pharmacist about your situation before using this product.
What side effects can L-Theanine cause?
The most common ones are headaches, drowsiness, longer sleep, and vivid dreams. A rare case of facial tics was reported in a child, but it stopped when the supplement was stopped — and that child had a history of tics, so a clear link wasn't established.
Why does this product interact with so many medications?
The 565 count reflects multiple medications across three drug categories: blood pressure meds, sedatives and CNS depressants (a large class), and antidepressants and other serotonergic drugs (also a large class). Many people take drugs from one or more of these groups, so the total is high even though the number of drug types is small.

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

Not sure if L-Theanine 200 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 200 mg label
Go deeper

The Full Monographs Behind L-Theanine 200 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 200 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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