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  • 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: 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). 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).

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

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Doctor's Best L-Theanine with Suntheanine

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Fit Powders L-Theanine

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GNC L-Theanine

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Healthy Origins L-Theanine

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Jarrow Formulas L-Theanine 200

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Life Extension Theanine XR Stress Relief

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Nature's Trove L-Theanine 200 mg

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Solgar L-Theanine 150 mg

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Sports Research [SR] L-Theanine

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Swanson L-Theanine

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Vitacost L-Theanine

You must join to see the full review and test results for L-theanine supplements along with recommendations and quality ratings. You'll get test results and quality ratings for 9 supplements selected for review by, plus 2 others which passed the same testing through'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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Additional Information
Tested through CL's Quality Certification Program prior to, or after initial posting of this Product Review.