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Dietary supplement

L-Theanine Ingredients & Drug Interactions

by NutraBio

L-Theanine label
See full label image
Capsule Category: Non-nutrient/non-botanical
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Oct 7, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking L-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

L-Theanine is a dietary supplement by NutraBio 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 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 L-Theanine by NutraBio

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

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HelloPharmacist Scorecard of L-Theanine by NutraBio

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 Oct 1, 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, an amino acid found naturally in green tea. L-Theanine is thought to promote relaxation and support cognitive function without causing drowsiness in most people.

The capsule also contains two inactive ingredients—hypromellose and water—which are used to form and fill the capsule shell.

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

This product doesn't appear to be marketed for a specific use, so we graded Theanine's overall clinical evidence instead.

Moderate

Some clinical evidence supports Theanine for:

Why this rating?
  • We looked at the product name, claims, and label statements and couldn't find a stated purpose to grade.
  • Since the label doesn't commit to one use, we graded the ingredient's overall clinical evidence instead.
  • On file: Cognitive function — rated "Possibly Effective" (Natural Medicines).

L-Theanine is rated possibly effective for supporting cognitive function. For other uses—age-related cognitive decline, Alzheimer's disease, generalized anxiety, OCD, and cancer—the evidence we hold is insufficient to make a reliable rating.

Talk with your doctor about what the research supports for your particular interest.

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. Common side effects include headaches, drowsiness, longer sleep duration, and more vivid dreams.

One pediatric case of facial tics was reported, though the child had a history of tics and they stopped when the supplement was discontinued. There isn't enough safety data during pregnancy or breastfeeding.

If you're pregnant, planning pregnancy, or breastfeeding, talk with your doctor or pharmacist before taking this product.

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.

Check with your doctor or pharmacist before adding this product if you take antihypertensive drugs (blood pressure medications)—theanine may lower your blood pressure further. Also flag it if you use CNS depressants (sedatives, sleeping pills, opioids) or serotonergic drugs (antidepressants), though the risk with those is smaller.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with some supporting evidence behind its ingredients' uses. Moderate medication interactions have been identified, and safety information is well characterized.

L-Theanine may help with focus and relaxation, but the evidence is solid only for cognitive function—and limited there. If you take blood pressure medication or sedative drugs, you'll want to check this with your doctor or pharmacist first, since theanine could amplify their effects.

For short-term use in otherwise healthy people, it's generally well tolerated, but long-term safety data is sparse.

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 May 23, 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 L-Theanine, straight from the product label.

Brand NutraBio
Barcode (UPC) 649908245160
Net contents 90 Capsule(s)
Market status On market
Date entered into DSLD May 23, 2024
DSLD ID 309350
Product type Non-nutrient/non-botanical
Supplement form Capsule
Dietary claims / uses Nutrient, All Other, Structure/Function
Intended target group(s) Vegetarian, Adult (18 - 50 Years), Kosher, Gluten 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 by NutraBio, 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 Vegetable Capsule(s)
Maximum serving Sizes:
1 Vegetable Capsule(s)
Servings per container
90
UPC/BARCODE
649908245160
IngredientAmount% DV
L-Theanine200 mg--

Other ingredients: Hypromellose, Water

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 use: Take 1 capsule 1-3 times daily, in divided doses, between meals.

Formulation

Vegetarian

Gluten free Non-GMO Lactose free

Manufactured in our GMP & FDA inspected facility

Promotes relaxation

Precautions

Warning: Not intended for use by persons under the age of 18. Keep out of the reach of children.

If you are pregnant, breast feeding, have known medical conditions (including kidney or liver disease) or are taking prescription OTC medication(s) consult with your health care practitioner before using this product.

Discontinue use two weeks prior to surgery.

Warning: Consuming this product can expose you to chemicals including lead, which are known to the State of California to cause birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov/food.

Processed in a facility and/or manufacturing line that also produces milk, tree nuts and nuts.

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)

NutraBio Since 1996

Seals/Symbols

Made In USA with Ingredients Sourced Worldwide

OU (Kosher)

FDA Statement of Identity

Amino Acid Supplement

Formula

OU (Kosher)

Storage

Store in a cool dry place.

General Statements

Product filled to this level

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

See for yourself

L-Theanine by NutraBio label

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

L-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 L-Theanine by NutraBio

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

Serving size1 Vegetable Capsule(s) Dosage formCapsule Servings per container90 Amounts shown are per serving.

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...

L-Theanine monograph & interactions

Other (inactive) ingredients: Hypromellose, Water. These complete the product’s ingredient list but are not active constituents.

Interaction report

L-Theanine by NutraBio Drug Interactions

Want to check YOUR meds against L-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

L-Theanine 565

Individual Drug Interactions

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

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

Each ingredient & the kinds of drugs it affects

For each ingredient in L-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.

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
L-Theanine full monograph & interactions
The maker

Brand information

Manufacturer and brand details for L-Theanine, from the product label.

NutraBio

See all NutraBio products
Name
NutraBio Labs, Inc.
Street Address
564 Lincoln Blvd.
City
Middlesex
State
NJ
ZipCode
08846
Phone Number
732-748-8606
Web Address
www.nutrabio.com
Pharmacist Counseling Corner

L-Theanine by NutraBio: Common Questions

Does L-Theanine by NutraBio interact with any medications?
Yes. Based on its ingredients, L-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?
L-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.
Can I take L-Theanine while pregnant or breastfeeding?
There isn't enough safety data to recommend it during pregnancy or breastfeeding. Talk with your doctor or pharmacist before taking it if you're pregnant, planning pregnancy, or nursing.
What are the side effects?
The most common are headaches and drowsiness. Some people also experience longer sleep or more vivid dreams. One rare case of facial tics was reported in a child, but they stopped once the supplement was discontinued.
Does L-Theanine actually work for anxiety or brain fog?
L-Theanine is possibly effective for cognitive function. For anxiety and age-related cognitive decline, the evidence we hold is insufficient to rate. It may help, but the research isn't solid enough yet to be certain.
What is L-Theanine and where does it come from?
L-Theanine is an amino acid naturally found in green tea. It's thought to promote calm focus—relaxation without the drowsiness you might get from a sedative.
Is this product safe for long-term use?
It's generally well tolerated for short-term use in healthy adults, but long-term safety hasn't been well studied. If you're thinking of taking it regularly for months, check with your doctor or pharmacist first.

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

Not sure if L-Theanine 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.

L-Theanine label
Go deeper

The Full Monographs Behind L-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

L-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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