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Dietary supplement

L-Theanine 200 mg Double Strength Ingredients & Drug Interactions

by Swanson

L-Theanine 200 mg Double Strength 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 200 mg Double Strength 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 Double Strength is a dietary supplement by Swanson 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 Double Strength by Swanson

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

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HelloPharmacist Scorecard of L-Theanine 200 mg Double Strength by Swanson

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, an amino acid that's naturally found in tea leaves. L-theanine is the form of theanine your body uses, and each capsule delivers 200 mg.

The capsule itself is made from hypromellose (a plant-based shell), with brown rice flour and magnesium stearate added as inactive ingredients to hold everything 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
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: supports calm focus and balanced mental health.
  • We looked for evidence on: Generalized anxiety disorder (GAD), Stress, Cognitive function, Insomnia, anxiety, mental clarity — 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), Insomnia, Stress.

L-theanine is possibly effective for supporting cognitive function — that's the strongest evidence we have. For age-related cognitive decline, Alzheimer's disease, generalized anxiety disorder, obsessive-compulsive disorder, and cancer, the evidence isn't established well enough yet to rate it either way.

If you're considering this product for one of those other uses, talk it over with your doctor about what the science actually shows right now.

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

There's one old case report of a child developing a facial tic while taking 400 mg daily, but it stopped when the supplement was discontinued — and that child had a history of tics, so it wasn't clear theanine caused it. There isn't enough safety data for pregnancy or breastfeeding, so the evidence advises against using this supplement if you're pregnant or nursing.

If you're in either situation and thinking about L-theanine, talk with your doctor or pharmacist for personalized advice.

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, check your medications against these types: blood pressure drugs (antihypertensives) — the Moderate concern here — sedating drugs (CNS depressants), and antidepressants or other serotonergic medications (Minor interactions). Use the search tool on this page to look up what you take.

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 may help with focus and mental clarity, and it's usually well tolerated. If you take blood pressure medication, sedating drugs, or antidepressants, check with your doctor or pharmacist before starting — theanine could interact with any of them.

Avoid it if you're pregnant or breastfeeding. Run your exact medications through the checker on this page to be sure.

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 Jun 24, 2019.

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 Double Strength, straight from the product label.

Brand Swanson
Barcode (UPC) 087614028163
Net contents 60 Veggie Cap(s)
Market status On market
Date entered into DSLD Jun 24, 2019
DSLD ID 204270
Product type Non-nutrient/non-botanical
Supplement form Capsule
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years)
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 Double Strength by Swanson, 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 Veggie Capsule(s)
Maximum serving Sizes:
1 Veggie Capsule(s)
UPC/BARCODE
087614028163
IngredientAmount% DV
Suntheanine L-Theanine200 mg--

Other ingredients: Brown Rice Flour, Hypromellose, 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.
General Statements

Supports balanced mental health and emotional wellbeing Maintains a feeling of calm while remaining alert Science-Backed Quality Since 1969

Brain and Nervous System Health 200 mg per capsule

Suggested/Recommended/Usage/Directions

Suggested use: As a dietary supplement, take one veggie capsule per day with water before meals.

Brand IP Statement(s)

Suntheanine is a registered trademark of Taiyo International, Inc.

Precautions

Warning: For adults only.

Consult your physician before using this or any product if you are pregnant or nursing, taking medication or have a medical condition.

Keep out of reach of children.

Do not use if seal is broken.

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.

FDA Statement of Identity

Dietary Supplement

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

See for yourself

L-Theanine 200 mg Double Strength by Swanson label

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

L-Theanine 200 mg Double Strength 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 Double Strength by Swanson

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

Serving size1 Veggie Capsule(s) Dosage formCapsule 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: Brown Rice Flour, Hypromellose, Magnesium Stearate. These complete the product’s ingredient list but are not active constituents.

Interaction report

L-Theanine 200 mg Double Strength by Swanson Drug Interactions

Want to check YOUR meds against L-Theanine 200 mg Double Strength?

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 Double Strength interact with 565 drugs. Click any drug to see the details.

1 of the 1 ingredient in L-Theanine 200 mg Double Strength 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 Double Strength 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 Double Strength, from the product label.

Swanson

See all Swanson products
Name
Swanson Health Products
City
Fargo
State
ND
ZipCode
58104
Phone Number
1-800-437-4148
Web Address
swanson.com
Pharmacist Counseling Corner

L-Theanine 200 mg Double Strength by Swanson: Common Questions

Does L-Theanine 200 mg Double Strength by Swanson interact with any medications?
Yes. Based on its ingredients, L-Theanine 200 mg Double Strength 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 Double Strength 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 does L-theanine actually do?
L-theanine is an amino acid that shows promise for supporting cognitive function — that's where the evidence is strongest. It won't work the same way in everyone, and we don't have solid proof yet for anxiety, mood, or cognitive aging.
Can I take this if I'm on blood pressure medication?
That depends on your specific drug and dose. Theanine might lower your blood pressure further, which could be a problem. Check with your doctor or pharmacist before adding it — they know your situation and can say whether it's safe for you.
What are the main side effects?
The most common ones reported are headaches, drowsiness, longer or more vivid dreams, and increased sleep. Most people tolerate it well, but these can happen — stop if they bother you and talk to your pharmacist.
Is this safe long-term?
It's generally well tolerated for short-term use in healthy adults, but we don't have good data on what happens if you take it for months or years. If you're thinking of using it long-term, ask your doctor whether it makes sense for you.
Can I take this while pregnant or breastfeeding?
There isn't enough safety data either way, so the evidence advises against it during pregnancy and breastfeeding. Talk with your doctor or pharmacist about your situation — they can help you decide what's right.

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 200 mg Double Strength label
Go deeper

The Full Monographs Behind L-Theanine 200 mg Double Strength’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 Double Strength'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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