ConsumerLab.com uses JavaScript to provide the best possible experience for our content, but your browser has it disabled. Learn how to enable it here.

About ConsumerLab.com

L-Theanine Supplements

Find the best L-theanine supplement and learn what this compound (also found in green and black tea) can and cannot do for stress, sleep, and blood pressure. Also learn about L-theanine dosage, safety, side effects and potential drug interactions.

L-Theanine Supplements Review

Search term may appear only in full report available to members. Join now for full access.

News Release

March 09, 2023

L-Theanine Supplements Reviewed by ConsumerLab. Top Pick Chosen.

  White Plains, New York, March 9, 2023 —L-theanine supplements are often promoted to reduce stress and improve sleep and cognition.

Product Review

GABA Supplements Review

Does GABA Work As a Supplement?

News Release

August 13, 2015

Feeling Stressed? ConsumerLab.com Reviews the Evidence for L-Theanine and Test Popular Products

White Plains, New York, August 21, 2015 — L-theanine is often promoted to reduce stress, and for conditions such as ADHD — but does it really work? ConsumerLab.com recently reviewed the evidence and purchased popular brands of L-theanine to test their quality.

Clinical Update

10/05/2019

L-Theanine for Sleep and Cognition?

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.

Clinical Update

5/16/2023

Solgar L-Theanine Approved

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.

CL Answer

Which supplements and lifestyle changes improve sleep, and which cause insomnia?

Find out which vitamins may help you sleep and learn if any vitamins or supplements can cause insomnia.

Product Review

Melatonin Supplements Review

Trouble Sleeping? See CL's Tests of Melatonin Supplements and Top Picks.

Melatonin Review 2024

Clinical Update

10/10/2023

L-theanine for Cognition?

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?

Clinical Update

1/12/2024

L-Theanine for Fatigue?

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?

Clinical Update

2/05/2019

Theanine for Anxiety?

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.

CL Answer

Can glycine improve sleep, reduce depression, or reduce nighttime urinary frequency?

Can glycine really help improve sleep, reduce depression, or reduce nighttime urinary frequency? Lean more about glycine and its uses and benefits.

Glycine for Sleep and Nighttime Urinary Frequency? -- Older Man Sitting on Bed, Awake at Night

Clinical Update

2/08/2022

L-Theanine for Stress?

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.

Product Review

CBD Oils, Softgels, Gummies, Creams & Salves Review

See How Much CBD and THC We Found in Products.

CL Answer

What is Brain Bright and can it really improve memory or cognition?

Learn more about BrainBright, including clinical studies on memory and cognition, safety, and cost.

CL Answer

Does Qualia Mind boost memory and mental function and is it worth cost?

Learn about the ingredients in Qualia Mind, whether or not we think the formula works and is safe, and if we think it's worth the cost.

qualia-mind

CL Answer

Do any supplements help relieve stress?

Are there actually supplements for stress relief and panic attacks? Learn more about holy basil, fish oil, L-theanine, and ginseng.

CL Answer

Does Alpha Brain really improve memory, focus and cognition?

Find out if Alpha Brain really improves memory, focus and cognition. See the clinical evidence and get details about Alpha Brain ingredients, as well as potential side effects and drug interactions. ConsumerLab.com's answer explains.

Bottle of Alpha Brain capsules

CL Answer

I find labels on supplement bottles misleading. For example, an L-theanine label says 200 mg on the front but the back says each pill contains just 100 mg, but a serving is 2 capsules. Is this legal?

Learn more about misleading supplement labels and legality, including labels that say "formulation," "blend," or "complex."

Misleading Supplement Labels -- woman reading supplement label

Product Review

Green Tea Review: Tea Bags, Matcha Powders, and Supplements

Some green teas provide barely any green tea polyphenols, while some others are high strength. See the Test Results and Our Top Picks for Green Tea.

Green Tea Review 2024

Product Review

Weight Loss Supplements Review (7-Keto DHEA, Forskolin and Stimulant Blend Supplements)

Choose the Best Weight Loss Supplement. Be Careful With Weight Loss Supplements — Few Pass Quality Testing and Safety Review.

Weight Loss Supplements Tested by ConsumerLab.com

CL Answer

Which supplements help to improve energy and decrease fatigue?

Energy supplements and vitamins - Some can help increase energy and reduce fatigue, including CoQ10, curcumin/turmeric, cocoa, and B vitamins.

Supplements to Improve Energy and Decrease Fatigue -- tired woman yawning at desk

CL Answer

What is the best way to take melatonin to get a good night's sleep?

Learn more about the best way to take melatonin for better sleep. When to take it, how to take it, and general melatonin information.

Melatonin Review 2024

Recalls & Warnings

February 17, 2022

Seller of L-Theanine, Lutein, Noopept and More Warned for Drug Claims

On February 4, 2022, the FDA issued a warning letter to Crystal Clear Supplements following a review of the company’s website and social media which found statements about Tianeptine Sodium Powder, Tianeptine Sulfate Powder, PEA Capsules, Phenibut Capsules, Synephrine Powder, Noopept ...

CL Answer

What are the best supplements for depression and anxiety?

Best natural supplements for depression and anxiety, including the evidence for fish oil, vitamin D, probiotics, and herbal supplements for depression such as curcumin (from turmeric) and saffron.

Best Supplements for Depression and Anxiety -- sad young woman sitting on couch, looking toward the window

CL Answer

What are the side effects of ashwagandha supplements?

Learn about the safety and side effects of ashwagandha supplements, including headache, sleepiness, upset stomach, blood pressure and more. ConsumerLab.com's answer explains.

ashwagandha side effects

Recalls & Warnings

January 18, 2024

FDA Warns Consumers Not to Use Neptune’s Fix Products

On November 21, 2023, the FDA warned consumers not to purchase or use Neptune’s Fix products because they contain tianeptine. The FDA has received severe adverse event reports after use of these products, including seizure and loss of consciousness.

Recalls & Warnings

July 11, 2014

Maker of Cough and Sleep "Remedies" Warned for Drug Claims

On June 27, 2014, the FDA issued a warning letter to Zarbee's, Inc.

Recalls & Warnings

July 27, 2012

Prescription and Street Drug Alternatives Found in Male Enhancement, Mood, and Sleep Supplements

On July 10, 2012, the FDA issued a warning letter to Evol Nutrition Associates, Inc. subsequent to a 2011 inspection which found a number of the company's products contained prescription and investigational drugs and were misbranded.

Recalls & Warnings

September 10, 2012

Maker of Concussion Recovery Supplement Warned For Making Drug Claims

On August 28, 2012, the FDA issued a warning letter to Trinity Sports Group, Inc. after a review of the company's websites found statements about Neuro Impact Concussion Response Formula constituted drug claims not permitted on supplements. 

Recalls & Warnings

December 26, 2012

Seller of Blood Sugar, Depression and Sleep Supplements Warned For Making Drug Claims

On October 15, 2012, the FDA issued a warning letter to BioNeurix Corporation after statements found on the company's website, http://www.pharma-tree.com, were found to promote the dietary supplements Blood Sugar 360, Amoryn, Seredyn, and Mellodyn as drugs.

Recalls & Warnings

June 12, 2014

Marketers of Memory Supplement Settle FTC Charges of Deceptive Claims

Martek Biosciences Corporation and i-Health Inc., marketers of BrainStrong Adult, have agreed to settle Federal Trade Commission (FTC) charges that claims the supplement could improve adult memory and prevent cognitive decline were deceptive, and not supported by sufficient clinical evidence.

Recalls & Warnings

May 30, 2015

Seller of Supplements for Herpes, Prostate Cancer & More Warned for Drug Claims

On May 7, 2015, the FDA issued a warning letter to Strictly Health Corporation, following a review of the company's websites which found statements made about FENVIR, Prosta Pep and Tonalin brand CLA to be drug claims.

Recalls & Warnings

March 15, 2013

Maker of Liquid Supplements Warned For Manufacturing Violations and Drug Claims

On January 31, 2013, the FDA issued a warning letter to Liquid Health, Inc.