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L-Theanine Supplements Review

Touted for Stress Relief, Do L-Theanine Supplements Work?

Latest Update
L-Theanine May Reduce Sleep
Tod Cooperman, M.D.

Medically reviewed and edited by Tod Cooperman, M.D.

 
Latest Update November 02, 2026 ⓘ
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Results of ConsumerLab.com Testing of L-Theanine Supplements

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Quick Summary

  • What is L-theanine?

    Often just called theanine, L-theanine, is a water-soluble amino acid found in black and green tea (see What It Is).

  • What are the health benefits of L-theanine?

    Some small clinical studies (funded by manufacturers of L-theanine) have found L-theanine may reduce stress, anxiety and blood pressure in stressful situations, but not all studies have found a benefit (see What It Does).

  • How much L-theanine should I take?

    L-theanine is typically taken at a dose of 200 mg to 400 mg per day (see Dosage).

  • Top Pick for L-theanine:

    ConsumerLab.com did not find problems with the quality of selected L-theanine products sold in the U.S., but did find large differences in the cost to obtain a 200-mg dose of L-theanine, which ranged from just 2 cents to as much as 50 cents (see What CL Found and How Products Were Evaluated). ConsumerLab selected a Top Pick based on dose, cost, and formulation.

  • L-theanine safety and side effects:

    At typical doses, L-theanine appears to be generally safe, but there are possible interactions with blood pressure medications and benzodiazepines (see Concerns and Cautions).
Products tested in 2023

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Alphabetical list of L-theanine supplement brands compared in this review

View Larger Image Doctor's Best L-Theanine with Suntheanine

Doctor's Best L-Theanine with Suntheanine

View Larger Image Fit Powders L-Theanine

Fit Powders L-Theanine

View Larger Image GNC L-Theanine

GNC L-Theanine

View Larger Image Healthy Origins L-Theanine

Healthy Origins L-Theanine

View Larger Image Jarrow Formulas L-Theanine 200

Jarrow Formulas L-Theanine 200

View Larger Image Life Extension Theanine XR Stress Relief

Life Extension Theanine XR Stress Relief

View Larger Image Nature's Trove L-Theanine 200 mg

Nature's Trove L-Theanine 200 mg

View Larger Image Solgar L-Theanine 150 mg

Solgar L-Theanine 150 mg

View Larger Image Sports Research [SR] L-Theanine

Sports Research [SR] L-Theanine

View Larger Image Swanson L-Theanine

Swanson L-Theanine

View Larger Image Vitacost L-Theanine

Vitacost L-Theanine

You must join to see the full review and test results for L-theanine supplements along with ConsumerLab.com recommendations and quality ratings. You'll get test results and quality ratings for 9 supplements selected for review by ConsumerLab.com, plus 2 others which passed the same testing through ConsumerLab.com's voluntary, Quality Certification Program. Plus, you'll learn:
 
  • Which L-theanine supplements failed ConsumerLab testing and which passed
  • ConsumerLab's Top Pick among L-theanine supplements based on quality and value
  • Differences in the marketed forms of L-theanine, such as Suntheanine, L-Tea Active, and Theanine XR
  • The clinical evidence for and against L-theanine supplementation for reducing stress and anxiety, lowering blood pressure, and improving sleep, mood and cognition
  • Potential side effects and drug interactions of L-theanine supplements
  • Tips for buying and using L-theanine, and more!

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Latest Clinical Research Updates for L-Theanine Supplements

L-Theanine May Reduce Sleep

May 21, 2024
A recent study of L-theanine suggests it may significantly reduce time asleep. See the details in the What It Does section of our L-Theanine Supplements Review, which includes our Top Picks.

L-Theanine for Fatigue?

January 12, 2024
Did drinking a beverage containing L-theanine, with or without CBD, reduce fatigue? See what a recent study showed in the Stress, sleep and cognition section of our L-Theanine Review, which includes our Top Picks for L-theanine.

Also see: Which supplements help to improve energy and decrease fatigue?

L-theanine for Cognition?

October 10, 2023

Does taking L-theanine (a compound that occurs naturally in tea) improve attention or cognition in healthy men and women? Find out in the What It Does section of our L-theanine Supplements Review, which includes our Top Picks for L-theanine.

Also see: Do any supplements, foods or lifestyle modifications help with brain function, like memory and cognition?

Solgar L-Theanine Approved

May 16, 2023

Solgar L-Theanine 150 mg was recently tested and Approved through our voluntary Quality Certification Program and was added to our L-Theanine Supplements Review.

L-Theanine for Stress?

February 08, 2022

Can L-theanine supplementation reduce stress during demanding tasks? See the latest evidence in the What It Does section of our L-Theanine Supplements Review.

L-Theanine for Sleep and Cognition?

October 05, 2019
Several studies have evaluated whether a single dose of L-theanine (found in green tea) can reduce stress and anxiety. A new study has evaluated the effect of L-theanine when taken daily for several weeks. See the results in the What It Does section of the L-Theanine Supplements Review. Also see our top choices for L-Theanine.

Theanine for Anxiety?

February 05, 2019
Theanine is promoted as an anxiety-reducing supplement, but does it really work? See results of a recent study in the What It Does section of the L-theanine Supplements Review. Also see our top choices for L-theanine supplements.

CoQ10 for Wrinkles

September 11, 2016
Taking a daily dose of CoQ10 may help to reduce facial wrinkles in older women, according to a preliminary study. Get the details and learn more about CoQ10 supplements in the "What It Does" section of the CoQ10 Supplements Review >>

Cocoa for Wrinkles?

November 24, 2015
A study in older women found that drinking a high-flavanol cocoa drink each day increased skin elasticity. And while wrinkles deepened among those drinking a placebo, they stayed stable in the cocoa-drinking group. For details about the amount of cocoa consumed (and its flavanol content), as well as our tests of flavanols (and contaminants) in popular cocoa powders and chocolates, see the Cocoa Powders, Dark Chocolate, Extracts, Nibs, & Supplements Review >>
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Additional Information
Tested through CL's Quality Certification Program prior to, or after initial posting of this Product Review.