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Dietary supplement

Suntheanine L-Theanine 100 mg Ingredients & Drug Interactions

by Natural Factors Stress-Relax

Suntheanine L-Theanine 100 mg label
See full label image
Tablet Or Pill 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 Natural Factors Stress-Relax 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 Suntheanine L-Theanine 100 mg by Natural Factors Stress-Relax

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

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HelloPharmacist Scorecard of Suntheanine L-Theanine 100 mg by Natural Factors Stress-Relax

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 Sep 17, 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, a form of the amino acid theanine at 100 mg per tablet. Theanine is a naturally occurring compound found in tea leaves.

The inactive ingredients are cane sugar, xylitol, stearic acid, silica, natural tropical flavor, citric acid, and magnesium stearate—typical tablet binders and fillers.

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: supports mental calmness and relaxation.
  • We looked for evidence on: Stress, Generalized anxiety disorder (GAD), Insomnia, anxiety, sleep quality, mental calm.
  • The closest evidence on file: Theanine is rated "Insufficient Reliable Evidence To Rate" for Generalized anxiety disorder (GAD) (Natural Medicines).
  • Also on file: Theanine is rated "Insufficient Reliable Evidence To Rate" for Insomnia, Stress.

The evidence for theanine on cognitive function is possibly effective based on available studies. However, for age-related cognitive decline, Alzheimer's 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—just that we don't yet have reliable data on file 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.

Theanine is generally well tolerated in healthy adults for short-term use, but we don't have solid data on long-term safety. The most common side effects reported are headaches, drowsiness, and changes to sleep patterns or dream activity.

There is not enough safety data during pregnancy or while breastfeeding, so the safety data advises against use in these situations. Talk with your doctor or pharmacist about whether this product is right for your circumstances.

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, confirm with your doctor or pharmacist that you are not taking blood pressure medications (antihypertensives), sedatives or sleep aids (CNS depressants), or serotonin-active antidepressants. Theanine may potentiate or combine with these drugs in ways that need individual review.

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.

Suntheanine L-Theanine may help with cognitive function based on current evidence, though proof for anxiety and other uses is not yet established. If you take blood pressure medications, sedatives, or certain antidepressants, check with your doctor or pharmacist before starting—theanine could amplify their effects.

It's generally well tolerated short-term but has not been studied long-term, and should be avoided during pregnancy and breastfeeding.

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 23, 2023.

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 Natural Factors Stress-Relax
Barcode (UPC) 068958028323
Net contents 60 Chewable Tablet(s)
Market status On market
Date entered into DSLD Jan 23, 2023
DSLD ID 282634
Product type Non-nutrient/non-botanical
Supplement form Tablet Or Pill
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Vegan, Vegetarian, 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 Suntheanine L-Theanine 100 mg by Natural Factors Stress-Relax, 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 Tablet(s)
Maximum serving Sizes:
2 Tablet(s)
Servings per container
30
UPC/BARCODE
068958028323
IngredientAmount% DV
Calories15 Calorie(s)--
Total Carbohydrates4 Gram(s)1%
Added Sugars3 Gram(s)6%
Total Sugars3 Gram(s)--
Suntheanine L-Theanine200 mg--

Other ingredients: Cane Sugar, Xylitol, Stearic Acid, Silica, Natural Tropical Flavor, Citric Acid, 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.
Seals/Symbols

isura Non-GMO - Mass spec Documentation - Lab tested

Purity & potency guaranteed

Suggested/Recommended/Usage/Directions

Suggested Usage: Chew 1-2 tablets 3 times per day or as directed by a health professional.

Precautions

Cautions: As with any supplement, consult your health professional before use if you are pregnant, breastfeeding, or trying to conceive, or if you are taking medication, have a medical condition, or anticipate surgery.

Keep out of the reach of children.

Sealed for your protection. Do not use if seal is broken.

Formula

Suntheanine contains pure L-Theanine, a unique amino acid found in green tea that is emerging as the premier natural product that supports mental calmness and relaxation. Suntheanine is produced via a proprietary enzymatic process guaranteeing essentially pure L-Theanine for maximum effectiveness. In a tasty tropical fruit-flavored chewable tablet.

Formulation

Manufactured by Natural Factors to ensure safety and potency in accordance with Good Manufacturing Practices (GMP) of the FDA and Health Canada.

Contains no artificial colors, preservatives, or sweeteners; no dairy, starch, wheat, gluten, yeast, soy, egg, fish, shellfish, animal products, salt, tree nuts, or GMOs.

Suitable for vegetarians/vegans.

Mental calmness & relaxation

Storage

For freshness, store in a cool, dry place.

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.

General Statements

Recyclable container and label.

FDA Statement of Identity

Dietary Supplement

Brand IP Statement(s)

Isura is a trademark of ISURA. Suntheanine is a registered trademark of Taiyo International, Inc.

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 Natural Factors Stress-Relax 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 Natural Factors Stress-Relax

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

Serving size1 Tablet(s) Dosage formTablet Or Pill Servings per container30 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: Cane Sugar, Xylitol, Stearic Acid, Silica, Natural Tropical Flavor, Citric Acid, Magnesium Stearate. These complete the product’s ingredient list but are not active constituents.

Interaction report

Suntheanine L-Theanine 100 mg by Natural Factors Stress-Relax 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 L-Theanine 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 L-Theanine

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.

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

Natural Factors Stress-Relax

See all Natural Factors Stress-Relax products
Name
Natural Factors
Street Address
14224 167th Avenue SE
City
Monroe
State
WA
ZipCode
98272
Pharmacist Counseling Corner

Suntheanine L-Theanine 100 mg by Natural Factors Stress-Relax: Common Questions

Does Suntheanine L-Theanine 100 mg by Natural Factors Stress-Relax 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 to know either way. The safety data advises against it during pregnancy and while breastfeeding. Talk with your doctor or pharmacist about your specific situation so they can give you personalized guidance.
What are the most common side effects?
Headaches are the most frequently reported side effect. Some people also report drowsiness, longer sleep duration, or more vivid dreams. These are usually mild, but let your doctor know if they bother you.
Is this supposed to help with anxiety?
For generalized anxiety disorder, the evidence we hold is insufficient to rate whether theanine works. You may see it marketed for stress and relaxation, but we don't yet have reliable proof. Your doctor or pharmacist can discuss what the current research actually shows.
How long can I safely take this?
Theanine is generally well tolerated in healthy adults for short-term use. Long-term safety hasn't been well studied, so if you're considering using it regularly for months or longer, run that plan by your doctor or pharmacist.
Will this make me sleepy?
Drowsiness is a reported side effect in some people, and theanine may have minor additive effects if you're also taking sedatives or sleep aids. If you're sensitive to drowsiness, start with a low dose and see how you feel.

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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Ask a pharmacist

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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