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Dietary supplement

L-Theanine 200 mg Ingredients & Drug Interactions

by Best Naturals

Tablet Or Pill 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 Best Naturals 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 Best Naturals

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 product contains a single active ingredient: L-theanine 200 mg per tablet. L-Theanine is an amino acid found naturally in tea that's known to support relaxation and mental clarity.

The remaining ingredients — dicalcium phosphate, microcrystalline cellulose, stearic acid, croscarmellose sodium, silicon dioxide, magnesium stearate, and pharmaceutical glaze — are inactive ingredients that help form and stabilize the tablet.

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: brain metabolism and cognitive function support.
  • We looked for evidence on: Cognitive function, Cognitive impairment, Age-related cognitive decline, Stress, Generalized anxiety disorder (GAD), Insomnia — and 3 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 Age-related cognitive decline, Generalized anxiety disorder (GAD), Cognitive impairment, Insomnia, and more.

L-Theanine is possibly effective for supporting cognitive function, according to the evidence we have on file. For other uses — age-related cognitive decline, Alzheimer disease, generalized anxiety disorder, obsessive-compulsive disorder, and cancer — there isn't enough reliable evidence to rate whether it works.

If you're considering it for one of those other purposes, talk with your doctor about what the current evidence actually shows.

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 well studied. The most common side effects reported are headaches, drowsiness, longer sleep duration, and increased dream activity.

One pediatric case of facial tics was reported, though the tics stopped when L-theanine was discontinued and the child had a prior history of tics, so the connection was unclear. Pregnancy and breastfeeding: there isn't enough safety data for either, so it's best to avoid L-theanine during pregnancy or while breastfeeding.

Talk with your doctor or pharmacist if you're pregnant, planning to become pregnant, or nursing.

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 taking L-Theanine if you use blood pressure medications — L-theanine may add to their effect. Also mention it if you take sedatives, sleep aids, or any other central nervous system depressants, or if you're on antidepressants or other serotonergic drugs, even though the interactions there are minor.

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 may help with cognitive function if that's what you're after, and it's generally well tolerated for short-term use in otherwise healthy people. The main caution is with blood pressure medications — L-theanine can lower blood pressure, which might be a problem if you're already on a blood pressure drug.

Before you add this to your routine, check with your doctor or pharmacist about your medications and whether this product makes sense for you.

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 Jul 21, 2022.

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 Best Naturals
Barcode (UPC) 817716018546
Net contents 120 Tablet(s)
Market status On market
Date entered into DSLD Jul 21, 2022
DSLD ID 269823
Product type Non-nutrient/non-botanical
Supplement form Tablet Or Pill
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years), Gluten 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 Best Naturals, 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 Tablet(s)
Maximum serving Sizes:
1 Tablet(s)
Servings per container
120
UPC/BARCODE
817716018546
IngredientAmount% DV
L-Theanine200 mg--

Other ingredients: Dicalcium Phosphate, Microcrystalline Cellulose, Stearic Acid, Croscarmellose Sodium, Silicon Dioxide, Magnesium Stearate, Pharmaceutical Glaze

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 a unique amino acid naturally found in green tea that exerts beneficial effects on brain metabolism. Animal studies have shown that L-theanine crosses the blood brain barrier, increases dopamine and GABA levels in the brain, and inhibits the stimulatory properties of caffeine. L-Theanine promotes relaxation without the drowsiness or negative side effects associated with other calming agents as measured by increased generation of alpha-waves. Certain research publications indicate that L-Theanine may help support the following: Supports healthy cardiovascular system. Supports healthy brain and nervous system. Supports learning ability. Supports relaxation and well-being.

Suggested/Recommended/Usage/Directions

Suggested Use: As a dietary supplement, take one (1) tablet one to two times daily as needed, preferably on empty stomach, or as directed by your qualified healthcare professional.

Precautions

Keep out of the reach of children.

Do not use if safety seal is broken or missing.

GMP Good Manufacturing Practice Product

Caution: For adults only, if you are pregnant, nursing, taking any medications or have any medical condition, consult your doctor before use.

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

Storage

Keep in cool, dry place.

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.

Seals/Symbols

Made in USA

Formulation

Premium formula

3rd party lab tested

No artificial color, flavor or sweetener, no preservatives, no sugar, no starch, no corn, no soy, no egg, no lactose, no gluten, no wheat, no yeast, no fish. Sodium free.

FDA Statement of Identity

Dietary Supplement

See for yourself

L-Theanine 200 mg by Best Naturals 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 Best Naturals

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

Serving size1 Tablet(s) Dosage formTablet Or Pill Servings per container120 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: Dicalcium Phosphate, Microcrystalline Cellulose, Stearic Acid, Croscarmellose Sodium, Silicon Dioxide, Magnesium Stearate, Pharmaceutical Glaze. These complete the product’s ingredient list but are not active constituents.

Interaction report

L-Theanine 200 mg by Best Naturals 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.

Best Naturals

See all Best Naturals products
Name
Best Naturals
Street Address
PO Box 394
City
Kenilworth
State
NJ
ZipCode
07033
Phone Number
1-877-659-6004
Web Address
www.shopbestnaturals.com
Pharmacist Counseling Corner

L-Theanine 200 mg by Best Naturals: Common Questions

Does L-Theanine 200 mg by Best Naturals 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?
There isn't enough safety data to know whether L-Theanine is safe during pregnancy or while breastfeeding. It's best to avoid it in both cases. Talk with your doctor or pharmacist about your individual situation.
What side effects should I watch for?
Headaches and drowsiness are the most commonly reported side effects. Some people also notice longer sleep duration or more vivid dreams. Stop taking it and let your doctor know if you have side effects that concern you.
How does L-Theanine help with cognitive function?
The evidence we have shows L-Theanine is possibly effective for cognitive function, but we don't have detailed information in our data on the specific mechanism. Your doctor or a clinical pharmacist can give you more details on how it's thought to work.
Is one 200 mg tablet enough, or do I need more?
We don't have dosing guidance in our data. Your doctor or pharmacist can advise on the right dose for your needs.
Can I take L-Theanine long-term?
L-Theanine is generally well tolerated for short-term use in healthy adults, but long-term safety hasn't been well studied. Talk with your doctor if you're thinking about taking it regularly for months or longer.

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

Not sure if L-Theanine 200 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 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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