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Dietary supplement

Suntheanine L-Theanine 100 mg Ingredients & Drug Interactions

by Swanson

Suntheanine L-Theanine 100 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 Suntheanine L-Theanine 100 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

Suntheanine L-Theanine 100 mg 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. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against Suntheanine L-Theanine 100 mg by Swanson

Ask about any prescription or over-the-counter medication and we check it for interactions with Suntheanine L-Theanine 100 mg by Swanson — and tell you which ingredient is responsible.

Pharmacist-reviewed data Checks every ingredient Answer in seconds
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HelloPharmacist Scorecard of Suntheanine L-Theanine 100 mg 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 Jul 11, 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, which is a branded form of L-theanine, an amino acid that naturally occurs in tea leaves. L-theanine works in the brain and is used to support cognitive function and calm.

The capsule also contains inactive ingredients — brown rice flour, hypromellose, and magnesium stearate — which are fillers and binders that help the capsule hold together and deliver the dose.

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 balanced mental health and emotional wellbeing.
  • We looked for evidence on: Generalized anxiety disorder (GAD), Stress, Depression, Insomnia, Cognitive function, Relaxation — and 2 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), Depression, Insomnia, Stress.

The evidence for L-theanine supporting cognitive function is rated as possibly effective based on the data we hold. For other uses — age-related cognitive decline, Alzheimer disease, generalized anxiety, obsessive-compulsive disorder, and cancer — the evidence is not yet established enough for us to rate it either way.

If cognition support is why you're interested, the science is suggestive but not conclusive. Talk with your pharmacist about whether it fits your goals.

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 long-term safety hasn't been thoroughly studied. Side effects people have reported include headaches, drowsiness, and increased sleep duration or vivid dreams.

A pediatric case of facial tics was reported, but it wasn't judged to be caused by the supplement since the child had a history of tics that stopped when theanine was stopped. There isn't enough safety data to recommend it during pregnancy or while breastfeeding — talk with your doctor or pharmacist for personalized guidance.

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 our search tool if you take blood pressure drugs — theanine may lower blood pressure further. Also flag any sedating medications (CNS depressants) or serotonergic drugs, though these interactions are less serious.

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.

This supplement may help with cognitive function, though evidence is still developing. If you take blood pressure medication or any sedating drugs, check with your pharmacist first — theanine could strengthen their effects.

It's generally well tolerated short-term in healthy adults, but long-term effects aren't well studied, and it's not recommended during pregnancy or breastfeeding without medical guidance.

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 21, 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 Suntheanine L-Theanine 100 mg, straight from the product label.

Brand Swanson
Barcode (UPC) 087614021102
Net contents 60 Veggie Capsule(s)
Market status On market
Date entered into DSLD Dec 21, 2024
DSLD ID 308776
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 Suntheanine L-Theanine 100 mg 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)
Servings per container
60
UPC/BARCODE
087614021102
IngredientAmount% DV
Suntheanine100 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.
Formulation

Supports balanced mental health and emotional wellbeing Maintains a feeling of calm while remaining alert

Brain and nervous system health

General Statements

Science-backed quality since 1969

Suggested/Recommended/Usage/Directions

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

Brand IP Statement(s)

Suntheanine is a registered trademark of Taiyo International, Inc.

Precautions

Warning: For adults only. Keep out of reach of children.

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

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

Formula

Suntheanine Suntheanine L-Theanine 100 mg per capsule

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

See for yourself

Suntheanine L-Theanine 100 mg by Swanson label

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

Suntheanine L-Theanine 100 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 Suntheanine L-Theanine 100 mg 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 Servings per container60 Amounts shown are per serving.

Suntheanine

Interacts with
565 drugs
100 mg per serving Form: L-Theanine

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 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

Suntheanine L-Theanine 100 mg by Swanson Drug Interactions

Want to check YOUR meds against Suntheanine L-Theanine 100 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 565

Individual Drug Interactions

The ingredients in Suntheanine L-Theanine 100 mg interact with 565 drugs. Click any drug to see the details.

1 of the 1 ingredient in Suntheanine L-Theanine 100 mg interact with drugs. Each result below shows which ingredient is responsible. Suntheanine

Each ingredient & the kinds of drugs it affects

For each ingredient in Suntheanine L-Theanine 100 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.

Suntheanine3 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 full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Suntheanine L-Theanine 100 mg, 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

Suntheanine L-Theanine 100 mg by Swanson: Common Questions

Does Suntheanine L-Theanine 100 mg by Swanson interact with any medications?
Yes. Based on its ingredients, Suntheanine L-Theanine 100 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?
Suntheanine L-Theanine 100 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.
Can I take this while pregnant or breastfeeding?
There isn't enough safety data on L-theanine during pregnancy or breastfeeding to recommend it. Talk with your doctor or pharmacist about what's best for you and your baby.
What side effects might I notice?
The most common are headaches, drowsiness, increased sleep duration, and more vivid dreams. These are mild for most people, but they're worth knowing about.
Does L-theanine actually help with brain fog or focus?
The evidence suggests it may help cognitive function, but it's not definitive yet. If cognition support is your goal, the science is promising but still developing.
How long has this been studied for safety?
L-theanine is generally well tolerated in healthy adults for short-term use, but long-term safety data is limited. If you plan to take it regularly for months or years, that's worth discussing with your pharmacist.
Is this the same as theanine from tea?
Yes — L-theanine is the amino acid naturally found in tea leaves. Suntheanine is a branded, purified form of it, so you're getting a concentrated, standardized dose rather than drinking tea.

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

Not sure if Suntheanine L-Theanine 100 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.

Suntheanine L-Theanine 100 mg label
Go deeper

The Full Monographs Behind Suntheanine L-Theanine 100 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

Suntheanine L-Theanine 100 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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