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Dietary supplement

L-Theanine (Double Strength) Ingredients & Drug Interactions

by Herbadiet

L-Theanine (Double Strength) label
See full label image
Capsule 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 L-Theanine (Double Strength) 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 (Double Strength) is a dietary supplement by Herbadiet 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 powder. 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 (Double Strength) by Herbadiet

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

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HelloPharmacist Scorecard of L-Theanine (Double Strength) by Herbadiet

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 powder (at double strength). L-theanine is an amino acid naturally found in tea that works in your brain to promote calm focus — it's not a stimulant and doesn't cause the jitters caffeine does.

The capsule itself is made from vegetable cellulose, an inert plant-based 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
Moderate

Some clinical evidence supports this product's ingredients for its stated purpose, but it isn't conclusive.

Why this rating?
  • The label markets this product for: promotes relaxation and supports healthy brain functions.
  • We looked for evidence on: Stress, Generalized anxiety disorder (GAD), Cognitive function, Insomnia, anxiety, mental clarity — and 1 related terms.
  • The strongest evidence on file: Theanine is rated "Possibly Effective" for Cognitive function (Natural Medicines).
  • Also on file: Theanine is rated "Insufficient Reliable Evidence To Rate" for Generalized anxiety disorder (GAD), Insomnia, Stress.

The evidence backs L-theanine as possibly effective for cognitive function — it may help with focus and mental clarity. For age-related cognitive decline, Alzheimer's disease, generalized anxiety, obsessive-compulsive disorder, and cancer, the evidence we hold isn't established enough to rate it.

If you're considering it for any of those uses, that's a conversation to have with your doctor.

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 closely. The most common side effects are headaches, drowsiness, longer sleep, 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, so causation wasn't clear. Pregnancy and breastfeeding: there isn't enough safety data, so it's best to avoid L-theanine during pregnancy and while breastfeeding — talk to your doctor or pharmacist about whether it's 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.

Check your blood pressure medications first — theanine can lower blood pressure and may make antihypertensive drugs work too well. Also double-check any sedating medications (sleep aids, anti-anxiety meds, certain pain relievers) and antidepressants or other serotonergic drugs before you start.

Your own doctor or pharmacist can tell you if any of your specific medications are on the list.

Check your own medication Run your meds through the checker above

The bottom line

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

L-Theanine is a single-ingredient supplement that's possibly effective for cognitive function and generally well tolerated short-term. It's most important to check with your doctor or pharmacist if you take blood pressure medications, sleep aids, anti-anxiety drugs, or antidepressants — theanine can interact with all of them.

If you're pregnant, breastfeeding, or have a history of tics, discuss it with your healthcare provider first.

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 Nov 19, 2021.

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 (Double Strength), straight from the product label.

Brand Herbadiet
Barcode (UPC) 880343499903
Net contents 60 V-Cap(s)
Market status On market
Date entered into DSLD Nov 19, 2021
DSLD ID 257750
Product type Non-nutrient/non-botanical
Supplement form Capsule
Dietary claims / uses Nutrient, 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 L-Theanine (Double Strength) by Herbadiet, 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 Capsule(s)
Maximum serving Sizes:
1 Capsule(s)
Servings per container
60
UPC/BARCODE
880343499903
IngredientAmount% DV
L-Theanine powder200 mg--

Other ingredients: Vegetable Cellulose Shell

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.
Formula

Herbadiet L-Theanine is a high potency pharmaceutical graade ingredient. This full spectrum amino acid retains all the active constituents in nature intended balanced ratio. Encapsulating this goodness in our quick release, easy to swallow vegan capsules, guarantees you a premium quality nutritional supplement.

Formulation

Promotes relaxation Healthy vascular function Supports healthy brain functions

Natural color variation may occur in this product

100% pure Supports protein digestion

Lab tested

Non-GMO

Free Of preservatives, binders, gluten, artificial ingredients, dairy, soy, wheat, yeast

Every batch 3rd party lab tested

FDA Disclaimer Statement

These statements have not been evaluated by FDA. This product is not intended to diagnose, treat, cure or prevent any disease.

Precautions

Do not use if seal under the cap is broken or missing. Dietary supplement shouldn't be used as a substitute for a varied diet

Caution: If you are pregnant, breast feeding, or taking medications, consult your doctor before use.

Discontinue use and consult your doctor if any adverse reactions occur.

Keep out of reach of children.

Not for medicinal use

Storage

Store in cool, dry place

Seals/Symbols

fssai Lic. No.: 20817018000147 Vcaps Plus GMP Good Manufacturing Practice Quality Product

General Statements

1% for the planet

License Number: 10018064001315

FDA Statement of Identity

Dietary Supplement

Suggested/Recommended/Usage/Directions

Directions for Use: Take 1 capsule twice a day, preferably on an empty stomach or as directed by your physician.

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

See for yourself

L-Theanine (Double Strength) by Herbadiet label

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

L-Theanine (Double Strength) 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 (Double Strength) by Herbadiet

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

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

L-Theanine powder

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 powder monograph & interactions

Other (inactive) ingredients: Vegetable Cellulose Shell. These complete the product’s ingredient list but are not active constituents.

Interaction report

L-Theanine (Double Strength) by Herbadiet Drug Interactions

Want to check YOUR meds against L-Theanine (Double Strength)?

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 powder 565

Individual Drug Interactions

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

1 of the 1 ingredient in L-Theanine (Double Strength) interact with drugs. Each result below shows which ingredient is responsible. L-Theanine powder

Each ingredient & the kinds of drugs it affects

For each ingredient in L-Theanine (Double Strength) 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-Theanine powder3 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 powder full monograph & interactions
The maker

Brand information

Manufacturer and brand details for L-Theanine (Double Strength), from the product label.

Herbadiet

See all Herbadiet products
Name
Arkure Health Care
City
Haryana
State
India
Web Address
www.herbadiet.in
Pharmacist Counseling Corner

L-Theanine (Double Strength) by Herbadiet: Common Questions

Does L-Theanine (Double Strength) by Herbadiet interact with any medications?
Yes. Based on its ingredients, L-Theanine (Double Strength) 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 (Double Strength) 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 if I'm on blood pressure medicine?
That's something to confirm with your doctor or pharmacist first. Theanine may lower blood pressure on its own, so combining it with blood pressure medications could push your pressure too low. Don't start without checking.
Will this make me drowsy?
Some people report drowsiness, longer sleep, or more vivid dreams after taking L-theanine. It's not guaranteed, but if you're sensitive to sedating effects, start low and see how you feel.
Can I take it while pregnant or breastfeeding?
There isn't enough safety data to know. The best advice is to avoid it during pregnancy and breastfeeding — talk to your doctor or pharmacist about what's safest for you and your baby.
Does it actually help with focus?
Yes, the evidence shows L-theanine is possibly effective for cognitive function. It may help you focus without the jittery feeling caffeine gives. For other uses like anxiety or age-related cognitive decline, the evidence isn't established yet.
What are the side effects?
Most common are headaches, drowsiness, longer sleep, and more vivid dreams. They're generally mild. One case of facial tics was reported in a child, but it stopped when the supplement was stopped.
Can I take it long-term?
Short-term safety is solid, but we don't have good long-term safety data. If you're thinking about taking it for months or years, ask your doctor or pharmacist whether that's right for you.

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

Not sure if L-Theanine (Double Strength) 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 (Double Strength) label
Go deeper

The Full Monographs Behind L-Theanine (Double Strength)’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 (Double Strength)'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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