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Dietary supplement

L-Theanine 200 mg Ingredients & Drug Interactions

by Nature's Lab

Capsule Category: Non-nutrient/non-botanical
Most serious interaction: Moderate
The interaction bottom line Most serious interaction: Moderate

L-Theanine 200 mg is a dietary supplement by Nature's Lab 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.

HelloPharmacist Scorecard of L-Theanine 200 mg by Nature's Lab

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

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 supplement contains one active ingredient: L-theanine 200 mg per capsule. L-theanine is an amino acid found naturally in tea that works in your brain to promote calm focus without heavy drowsiness.

The capsule itself is made up of inactive ingredients — rice flour, gelatin, magnesium stearate, and silicon dioxide — that help form and stabilize the supplement.

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

L-theanine has possibly effective evidence for supporting cognitive function — the kind of mental sharpness and clarity people often seek. For other uses listed in the research, including age-related cognitive decline, Alzheimer disease, generalized anxiety disorder, obsessive-compulsive disorder, and cancer, the evidence we hold is insufficient to draw a conclusion.

That doesn't mean it doesn't work for those — just that we don't have enough reliable data yet to say either way.

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, though long-term safety hasn't been well studied, so we don't know what happens if you take it for years. Some people report headaches, drowsiness, longer sleep, or more vivid dreams after taking it.

One pediatric case of a subtle facial tic was reported shortly after starting 400 mg daily, but it stopped when the supplement was discontinued — and because the child had a history of tics, the link was unclear. There isn't enough safety data to know whether L-theanine is safe in pregnancy or while breastfeeding.

The facts advise against using it during pregnancy and lactation; talk with your doctor or pharmacist for personalized guidance.

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 blood pressure medications (antihypertensives) first — theanine can lower blood pressure and might potentiate their effect. Also flag any CNS depressants like sleep aids or anti-anxiety drugs, and serotonergic medications like antidepressants, though the latter two are Minor concerns.

Use the medication checker below to see if your specific drugs are listed.

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 help with focus and mental clarity if the research holds up for you. If you're on blood pressure medication or take sleep aids, antidepressants, or other CNS depressants, check your exact drugs with the tool on this page first.

For pregnancy, breastfeeding, or long-term use, a conversation with your pharmacist or doctor is worth having.

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, 2025.

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 200 mg, straight from the product label.

Brand Nature's Lab
Barcode (UPC) 818014014025
Net contents 60 Easy-To-Swallow Capsule(s)
Market status On market
Date entered into DSLD Sep 25, 2025
DSLD ID 334720
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, 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 200 mg by Nature's Lab, 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
818014014025
IngredientAmount% DV
L-Theanine200 mg--

Other ingredients: Rice Flour, Gelatin, Magnesium Stearate, Silicon Dioxide

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

L-theanine is an amino acid found primarily in certain plant species and is a constituent of green tea. L-theanine works to support mental calmness and relaxation without producing drowsiness by blocking excitatory stimuli receptors to the brain. L-Theanine may also help regulate blood pressure within normal limits and promote healthy cognitive function.

L-Theanine 200 mg per serving

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.

Precautions

Warnings: Pregnant or lactating women and people with known medical conditions and/or taking drugs should consult with a qualified healthcare practitioner prior to taking dietary supplements.

Do not use if seal is broken.

Keep out of reach of children.

Manufactured in a facility that also processes soy, milk, fish and shellfish.

Formulation

Supports mental calmness

Free of: Sugar, Salt, Dairy, Eggs, Peanuts, Tree Nuts, Fish, Shellfish, Yeast, Wheat, Soy, Gluten, Titanium Dioxide, Artificial Colors and Flavors.

FDA Statement of Identity

Dietary Supplement

Suggested/Recommended/Usage/Directions

Suggested Use: As a dietary supplement, take 1 capsule one time daily, preferably with a meal, or as directed by a qualified healthcare practitioner.

Storage

Store in a cool, dry place.

See for yourself

L-Theanine 200 mg by Nature's Lab label

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

What’s inside

The Ingredients in L-Theanine 200 mg by Nature's Lab

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

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: Rice Flour, Gelatin, Magnesium Stearate, Silicon Dioxide. These complete the product’s ingredient list but are not active constituents.

Interaction report

L-Theanine 200 mg by Nature's Lab Drug Interactions

Want to check YOUR meds against L-Theanine 200 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

Each ingredient & the kinds of drugs it affects

For each ingredient in L-Theanine 200 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.

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
The maker

Brand information

Manufacturer and brand details for L-Theanine 200 mg, from the product label.

Nature's Lab

See all Nature's Lab products
Name
Nature's Lab
Street Address
6980 W. Warm Springs Road, Suite 100
City
Las Vegas
State
NV
ZipCode
89113
Phone Number
1-888-793-0351
Web Address
Natureslab.com
Pharmacist Counseling Corner

L-Theanine 200 mg by Nature's Lab: Common Questions

Does L-Theanine 200 mg by Nature's Lab interact with any medications?
Yes. Based on its ingredients, L-Theanine 200 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 200 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 L-theanine if I'm pregnant or breastfeeding?
No — there isn't enough safety data, so the guidance is to avoid it during pregnancy and while breastfeeding. Talk with your doctor or pharmacist about what's right for your situation.
Will L-theanine make me drowsy?
Some people report drowsiness, increased sleep duration, and more vivid dreams. It's designed to promote calm focus, but your individual response may vary — start with a low dose if you're sensitive to sedative effects.
What is L-theanine supposed to do?
It's an amino acid from tea that's possibly effective for supporting cognitive function — mental sharpness and focus. For other uses like anxiety or age-related cognitive decline, the evidence we hold is not yet reliable enough to say.
Is this safe to take long-term?
L-theanine is generally well tolerated in healthy adults for short-term use, but long-term safety hasn't been well studied. If you're planning to take it regularly for months or longer, check with your pharmacist first.
What are the side effects?
The most common ones reported are headaches, drowsiness, increased sleep, and vivid dreams. One pediatric case of a brief facial tic was reported but was unclear whether it was caused by theanine.

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

Not sure if L-Theanine 200 mg is safe with your meds?

Our pharmacists answer your medication & supplement questions — free.

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 200 mg label
Go deeper

The Full Monographs Behind L-Theanine 200 mg’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Sources

Sources & How We Checked

L-Theanine 200 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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