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Dietary supplement

L-Theanine 100 mg Ingredients & Drug Interactions

by Meijer

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 16, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking 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

L-Theanine 100 mg is a dietary supplement by Meijer 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 L-Theanine 100 mg by Meijer

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

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HelloPharmacist Scorecard of L-Theanine 100 mg by Meijer

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: L-theanine 100 mg per capsule, supplied as SunTheanine. Theanine is an amino acid found naturally in tea leaves and has been studied for its effects on relaxation and mental clarity without causing drowsiness on its own.

The capsule also contains several inactive ingredients (cellulose, water, magnesium stearate, and silica) that serve as the capsule shell and help with tablet binding and flow.

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: relaxation and deep, restful sleep.
  • We looked for evidence on: Insomnia, Stress, Generalized anxiety disorder (GAD), sleep quality, anxiety relief.
  • 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.

L-theanine is rated possibly effective for supporting cognitive function. For other uses — age-related cognitive decline, Alzheimer disease, generalized anxiety disorder, obsessive-compulsive disorder, and cancer — the evidence we hold is insufficient to make a reliable rating, meaning studies haven't been conclusive enough to know whether it works for those purposes.

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 studied well. The most common side effects reported are headaches and drowsiness; some people have also reported increased sleep duration and more vivid dreams.

Based on the safety data available, theanine is best avoided during pregnancy and while breastfeeding — there isn't enough information to know it's safe in these situations. Talk with your doctor or pharmacist if you're pregnant, planning to become pregnant, or breastfeeding and considering this supplement.

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 you start, double-check any blood pressure medications you're on — theanine might lower your pressure further. Also flag any sedating drugs (sleep aids, anxiety medications, certain pain relievers) and serotonergic antidepressants so your doctor or pharmacist can weigh the risks with you.

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 be worth trying if you're interested in cognitive support and generally tolerate it well, but it's not right for everyone. If you take blood pressure medication or sedating drugs, check with your doctor or pharmacist first — theanine could strengthen those effects.

Start by reviewing your current medications using the tool on this page, then have a conversation with your healthcare provider about whether it fits your routine.

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 Sep 25, 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 L-Theanine 100 mg, straight from the product label.

Brand Meijer
Barcode (UPC) 760236103592
Net contents 60 Veggie Capsule(s)
Market status On market
Date entered into DSLD Sep 25, 2023
DSLD ID 296570
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 100 mg by Meijer, 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 Vegetarian Capsule(s)
Maximum serving Sizes:
1 Vegetarian Capsule(s)
Servings per container
60
UPC/BARCODE
760236103592
IngredientAmount% DV
SunTheanine100 mg--

Other ingredients: Cellulose, Water, Cellulose, Magnesium Stearate, Silica

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.
FDA Statement of Identity

Dietary Supplement

Formulation

General Health

No sugar, salt, dairy, yeast, wheat, gluten, soy, preservatives, artificial colors or flavors.

Natural color variations may occur in this product.

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.

Brand IP Statement(s)

From SunTheanine, as 100% pure, patented source of L-Theanine manufactured in Japan by Taiyo International.

Formula

SunTheanine has been extensively evaluated in many scientific studies and shown to support relaxation and deep, restful sleep without causing drowsiness or other unwanted side effects.

Suggested/Recommended/Usage/Directions

Suggested Use: As a dietary supplement, adults take one (1) vegetarian capsule, one (1) to three (3) times daily, or as directed by a health care professional.

Storage

Store in a cool, dry place and away from direct light.

Precautions

Keep out of reach of children.

General Statements

Our Quality Guarantee www.meijer.com/satisfaction The Meijer Family

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

See for yourself

L-Theanine 100 mg by Meijer label

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

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 L-Theanine 100 mg by Meijer

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

Serving size1 Vegetarian Capsule(s) Dosage formCapsule Servings per container60 Amounts shown are per serving.

SunTheanine

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

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: Cellulose, Water, Cellulose, Magnesium Stearate, Silica. These complete the product’s ingredient list but are not active constituents.

Interaction report

L-Theanine 100 mg by Meijer Drug Interactions

Want to check YOUR meds against 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 L-Theanine 100 mg interact with 565 drugs. Click any drug to see the details.

1 of the 1 ingredient in 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 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 L-Theanine 100 mg, from the product label.

Meijer

See all Meijer products
Name
Meijer Distribution, Inc.
City
Grand Rapids
State
MI
ZipCode
49544
Phone Number
1-800-879-8623
Web Address
www.meijer.com
Pharmacist Counseling Corner

L-Theanine 100 mg by Meijer: Common Questions

Does L-Theanine 100 mg by Meijer interact with any medications?
Yes. Based on its ingredients, 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?
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?
The safety data for theanine during pregnancy and breastfeeding is insufficient, so it's best to avoid it in both situations. Talk with your doctor or pharmacist about whether this supplement is appropriate for you if you're pregnant, planning to become pregnant, or breastfeeding.
What side effects might I experience?
The most common are headaches and drowsiness. Some people have reported sleeping longer or having more vivid dreams. Side effects tend to be mild, but if they're bothersome or don't settle, stop taking it and speak with a pharmacist.
Does this really help with focus or anxiety?
Theanine is rated possibly effective for cognitive function based on available research. For anxiety and other uses, the evidence we hold isn't strong enough to say it works — studies have been inconclusive so far.
Is it safe to take long-term?
Short-term use in healthy adults is generally well tolerated, but long-term safety hasn't been thoroughly studied. If you're thinking about taking it regularly over months or longer, discuss that plan with your doctor or pharmacist.
Will this make me drowsy?
Theanine itself isn't designed to cause drowsiness — it's promoted for calm focus — but some people do report drowsiness as a side effect. If you're sensitive to sedating effects, start low and see how you respond, and avoid combining it with sleep aids or other sedating medications without checking first.

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

Not sure if 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.

L-Theanine 100 mg label
Go deeper

The Full Monographs Behind 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

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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