Interactions on record — worth a quick check against your medications. Based on 1 of 2 ingredients. Check your meds →
Dietary supplement

Stress-Relax Suntheanine Ingredients & Drug Interactions

by Natural Factors

Stress-Relax Suntheanine 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 Stress-Relax Suntheanine 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

Stress-Relax Suntheanine is a dietary supplement by Natural Factors with 2 active ingredients. 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 Stress-Relax Suntheanine by Natural Factors

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

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HelloPharmacist Scorecard of Stress-Relax Suntheanine by Natural Factors

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. Theanine is derived from tea and is believed to promote relaxation without drowsiness.

The tablet also contains inactive ingredients including cane sugar, xylitol, stearic acid, silica, natural fruit flavor, citric acid, and magnesium stearate.

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: support mental calmness and relaxation.
  • We looked for evidence on: Stress, Generalized anxiety disorder (GAD), Insomnia, anxiety, calm, relaxation.
  • 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.

For cognitive function, theanine is rated possibly effective — there's some evidence it may help, but it's not definitive. For other uses like age-related memory loss, Alzheimer disease, generalized anxiety, OCD, and cancer, the evidence we have isn't established enough to rate.

If you're taking this for one of those other reasons, the science doesn't support it yet.

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 how safe it is over the long haul isn't well studied. The most common side effects reported are headaches, drowsiness, increased sleep time, and more vivid dreams.

One case of facial tics was reported in a child taking 400 mg daily, though the tics stopped when theanine was stopped and the child had a history of tics. There isn't enough safety data during pregnancy or while breastfeeding, so the guidance is to avoid this supplement if you're pregnant or nursing.

Talk with your doctor or pharmacist about whether this is right for you in those situations.

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, double-check with your doctor or pharmacist if you're on blood pressure medication — theanine can enhance its effect. Also flag any CNS depressants (sleep aids, anti-anxiety drugs) or serotonergic medications (certain antidepressants) you're taking, though the risks are less clear-cut.

No interactions are documented for ingredients we couldn't check — but that doesn't mean none exist.

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.

Stress-Relax Suntheanine may help with focus and thinking — the evidence leans that way but isn't rock solid. It's generally well tolerated short-term, but if you take blood pressure medication, a sleep aid, an anxiety drug, or an antidepressant, you need to check with your doctor or pharmacist before starting this.

Pregnant or nursing? Skip it until you've talked it over with your healthcare provider.

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 Aug 26, 2014.

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 Stress-Relax Suntheanine, straight from the product label.

Brand Natural Factors
Barcode (UPC) 068958283135
Net contents 10 Chewable Tablet(s)
Market status On market
Date entered into DSLD Aug 26, 2014
DSLD ID 36590
Product type Non-nutrient/non-botanical
Supplement form Tablet Or Pill
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 Stress-Relax Suntheanine by Natural Factors, 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
5
UPC/BARCODE
068958283135
IngredientAmount% DV
Calories15 {Calories}--
Total Carbohydrates4 Gram(s)1%
Sugar3 Gram(s)--
Suntheanine L-Theanine200 mg--

Other ingredients: Cane Sugar, Xylitol, Stearic Acid, Silica, natural Fruit 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.
Suggested/Recommended/Usage/Directions

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

Precautions

Keep out of reach of children.

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

Brand IP Statement(s)

Suntheanine(R) contains pure L-Theanine, a unique amino acid found in green tea that is emerging as the premier natural product to support mental calmness and relaxation.* Suntheanine(R) is produced via a proprietary enzymatic process, guaranteeing essentially pure L-Theanine for maximum effectiveness.* In a tasty fruit-flavored chewable tablet. All Natural Factors products are manufactured in accordance with the Government of Canada's Good Manufacturing Practices (GMP), among the highest standards in the world.

Suntheanine(R) is a registered trademark of Taiyo International, Inc.

Formulation

Contains no artificial preservatives, color or sweeteners; no dairy, gluten, soy, wheat or yeast.

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

PRODUCT OF CANADA

Recyclable container and label.

For Mental Calmness & Relaxation* Recommended by Dr. Michael Murray

Seals/Symbols

Purity&Potency Guaranteed

Suntheanine(R)

FDA Statement of Identity

DIETARY SUPPLEMENT

Formula

L-Theanine

General

R0

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

See for yourself

Stress-Relax Suntheanine by Natural Factors label

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

Stress-Relax Suntheanine 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 Stress-Relax Suntheanine by Natural Factors

These are the 2 active ingredients this product is made of. Select any to open its full monograph.

Serving size1 Tablet(s) Dosage formTablet Or Pill Servings per container5 Amounts shown are per serving.

Most supplement products combine several ingredients, and a medication can interact with the product through any one of them. Each ingredient below shows whether it has known drug interactions.

Sugar

3 Gram(s) 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 Fruit Flavor, Citric Acid, Magnesium Stearate. These complete the product’s ingredient list but are not active constituents.

Interaction report

Stress-Relax Suntheanine by Natural Factors Drug Interactions

Want to check YOUR meds against Stress-Relax Suntheanine?

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 Stress-Relax Suntheanine interact with 565 drugs. Click any drug to see the details.

1 of the 2 ingredients in Stress-Relax Suntheanine 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 Stress-Relax Suntheanine 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 Stress-Relax Suntheanine, from the product label.

Natural Factors

See all Natural Factors products
Name
Natural Factors Canada
Pharmacist Counseling Corner

Stress-Relax Suntheanine by Natural Factors: Common Questions

Does Stress-Relax Suntheanine by Natural Factors interact with any medications?
Yes. Based on its ingredients, Stress-Relax Suntheanine 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?
Stress-Relax Suntheanine contains 2 active ingredients, and an interaction can come from any of them. We check every ingredient, combine the results into one list per medication, and show which ingredient and mechanism is 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 this help me focus better?
Theanine is rated possibly effective for cognitive function, meaning there's some evidence it may help, but it's not conclusive. It's not proven for age-related memory loss or Alzheimer disease.
Can I take this if I'm on blood pressure medication?
Theanine can lower blood pressure, so combining it with blood pressure drugs might drop your pressure too far. Talk with your doctor or pharmacist before adding this — they'll know your exact meds and blood pressure numbers.
Is it safe to take long-term?
Theanine is generally well tolerated for short-term use in healthy adults, but long-term safety hasn't been well studied. If you plan to take it for months, check with your doctor or pharmacist about what's known and what isn't.
What side effects might I notice?
Headaches, drowsiness, and more vivid dreams are the most commonly reported side effects. One child developed facial tics on a high dose, though they stopped when the supplement was discontinued.
Can I take this while pregnant or breastfeeding?
There isn't enough safety data to say yes, so it's best to avoid it during pregnancy and while breastfeeding. Talk with your doctor or pharmacist about your options.
Can I combine this with my anxiety medication or sleep aid?
Theanine might theoretically add to the sedative effects of CNS depressants like sleep aids and anti-anxiety drugs, though it's unclear if this is a real problem in practice. Check with your doctor or pharmacist before combining them.

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

Not sure if Stress-Relax Suntheanine 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.

Stress-Relax Suntheanine label
Go deeper

The Full Monographs Behind Stress-Relax Suntheanine’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

Stress-Relax Suntheanine'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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