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Dietary supplement

Theanine Ingredients & Drug Interactions

by Natrol

Theanine label
See full label image
Tablet Or Pill Category: Amino Acid/protein
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 9, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Theanine 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

Theanine is a dietary supplement by Natrol 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 Theanine by Natrol

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

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HelloPharmacist Scorecard of Theanine by Natrol

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 L-Theanine. L-theanine is an amino acid found naturally in tea that's thought to support relaxation and mental focus.

The tablet also contains several inactive ingredients — cellulose, cellulose gum, stearic acid, silica, magnesium stearate, methylcellulose, glycerin, and carnauba wax — which are fillers, binders, and coating materials used to make the tablet stable and easy to swallow.

Does it work?

Insufficient 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
Insufficient

There isn't enough reliable clinical evidence to rate this product's ingredients for its stated purpose.

Why this rating?
  • The label markets this product for: reduce stress and anxiety, promote relaxation.
  • We looked for evidence on: Generalized anxiety disorder (GAD), Stress, Anxiety, Mood.
  • The closest evidence on file: Theanine is rated "Insufficient Reliable Evidence To Rate" for Anxiety (Natural Medicines).
  • Also on file: Theanine is rated "Insufficient Reliable Evidence To Rate" for Generalized anxiety disorder (GAD), Stress.

L-theanine has possibly effective evidence for cognitive function — meaning some research supports it, but the evidence isn't conclusive yet. For age-related cognitive decline, Alzheimer disease, generalized anxiety disorder, obsessive-compulsive disorder, and cancer, the evidence we have is insufficient to rate whether it works.

If cognition support is your goal, theanine may be worth a try, but talk with your pharmacist about what the research actually shows and whether it fits your situation.

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. Long-term safety hasn't been well studied, so we don't know what happens if you take it for months or years.

The most common reported side effects are headaches, drowsiness, longer sleep duration, and more vivid dreams. One child experienced a facial tic while taking 400 mg daily, but the tic had happened before, so it wasn't clearly tied to theanine.

There isn't enough safety data to know whether L-theanine is safe during pregnancy or breastfeeding. If you're pregnant or nursing, talk with your doctor or pharmacist about whether this product is right for you.

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 take Natrol Theanine, check any blood pressure medications (antihypertensives) you're on — theanine can lower blood pressure and might potentiate their effect. Also check sedating drugs (CNS depressants like sleep aids or antihistamines) for a possible additive drowsy effect, and any serotonergic drugs (antidepressants and similar) as a precaution, though direct harm reports are absent.

Use the medication search tool on this page with your full list.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with insufficient evidence for its stated purpose. Moderate medication interactions have been identified, and safety information is well characterized.

Natrol Theanine may help with focus and mental clarity if you're looking for a mild cognitive boost, though the evidence is still emerging. If you take blood pressure medication or any sedating drug, check your exact medications with the tool on this page before starting — theanine could potentially strengthen their effects.

A brief conversation with your pharmacist about how this fits your health picture is always a smart move.

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 Oct 26, 2011.

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 Theanine, straight from the product label.

Brand Natrol
Barcode (UPC) 047469162306
Net contents 60 Tablet(s)
Market status On market
Date entered into DSLD Oct 26, 2011
DSLD ID 1283
Product type Amino Acid/protein
Supplement form Tablet Or Pill
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Vegetarian, 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 Theanine by Natrol, 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:
2 Tablet(s)
Maximum serving Sizes:
2 Tablet(s)
Servings per container
30
UPC/BARCODE
047469162306
IngredientAmount% DV
Suntheanine L-Theanine150 mg--

Other ingredients: Cellulose, Cellulose Gum, Stearic Acid, Silica, Magnesium Stearate, Methylcellulose, Glycerin, Carnauba wax

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.
Brand IP Statement(s)

Natrol(R) Theanine works to reduce stress and anxiety. This 100% vegetarian, natural mood enhancer promotes relaxation without drowsiness.+

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

Formulation

NO Yeast, Wheat, Corn, Milk, Egg, Soy, Glutens, Artificial Colors or Flavors, Added Sugar, Starch or Preservatives

Precautions

Consult your healthcare professional prior to use if you have or suspect a medical condition, or are taking prescription drugs, or are pregnant or lactating.

Storage

STORE IN A COOL, DRY PLACE. KEEP OUT OF REACH OF CHILDREN.

General Statements

- May Help Reduce Stress and Anxiety+ - Natural Mood Enhancer+

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

General

ITEM: 16230 F: 3000124 L: 2004339-8067

Suggested/Recommended/Usage/Directions

Directions: Take 2 tablets, one time daily or every 8 hours as needed.

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

See for yourself

Theanine by Natrol label

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

Theanine 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 Theanine by Natrol

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

Serving size2 Tablet(s) Dosage formTablet Or Pill Servings per container30 Amounts shown are per serving.

Suntheanine L-Theanine

Interacts with
565 drugs
150 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: Cellulose, Cellulose Gum, Stearic Acid, Silica, Magnesium Stearate, Methylcellulose, Glycerin, Carnauba wax. These complete the product’s ingredient list but are not active constituents.

Interaction report

Theanine by Natrol Drug Interactions

Want to check YOUR meds against Theanine?

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

1 of the 1 ingredient in Theanine 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 Theanine 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 Theanine, from the product label.

Natrol

See all Natrol products
Name
Natrol, Inc.
City
Chatsworth
State
CA
ZipCode
91311
Phone Number
800-262-8765
Web Address
www.natrol.com
Pharmacist Counseling Corner

Theanine by Natrol: Common Questions

Does Theanine by Natrol interact with any medications?
Yes. Based on its ingredients, Theanine 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?
Theanine 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 is L-theanine, and what is it supposed to do?
L-theanine is an amino acid found in tea that's thought to support cognitive function and mental focus. There's some evidence it works for cognition, though the research isn't definitive yet.
What are the most common side effects?
Headaches, drowsiness, longer or more vivid dreams, and increased dream activity have been reported. Most people tolerate it well in the short term.
Is it safe to take while I'm pregnant or breastfeeding?
There isn't enough safety data either way. Talk with your doctor or pharmacist — they can help you weigh the unknowns against your individual needs.
How long has the safety of L-theanine been studied?
Short-term safety in healthy adults is fairly well documented, but long-term safety — what happens if you take it for months or years — hasn't been well studied.
Does this product have fillers or other inactive ingredients?
Yes. It contains cellulose, cellulose gum, stearic acid, silica, magnesium stearate, methylcellulose, glycerin, and carnauba wax as inactive ingredients — standard binding and coating materials.

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.

Theanine label
Go deeper

The Full Monographs Behind Theanine’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

Theanine'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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