Reviews and Information for L-Glutamine
L-Glutamine Supplements
Read our review to find the best glutamine (l-glutamine) supplements, avoid pitfalls with labels, and learn whether glutamine helps for boosting the immune system, improving exercise performance, and protecting the stomach from NSAIDS. Plus glutamine dosage, safety and side-effect information. Find out which ones passed our tests and why.
L-Glutamine Supplements Review
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Product Review
Muscle & Workout Supplements Review (Creatine and Branched-chain Amino Acids)
Do Creatine and BCAAs Really Improve Strength and Recovery?
News Release
March 13, 2025
Best L-Glutamine Supplements According to ConsumerLab Tests
White Plains, NY, March 13, 2025 — L-glutamine (glutamine) supplements are promoted to boost energy and the immune system and for other benefits, but do they really work, and if so, which glutamine products on the market are best?
Product Review
Protein Powders, Shakes, and Meal Replacements Review
Find Out Which Protein Products Passed or Failed Our Tests
Product Review
Electrolytes & Sports Drinks Review
See Which Sports Drinks, Powders, and Pills Deliver the Right Electrolytes
Clinical Update
9/30/2022
Glutamine Side Effects
A CL Member experienced dizziness, nausea, and anxiety after taking L-glutamine. Find out if these are known side effects of L-glutamine, and learn about other potential adverse effects of glutamine in the Concerns and Cautions section of our Muscle & Workout Supplements Review.
Also see our article about supplements that may cause dizziness.
Product Review
Multivitamin and Multimineral Supplements Review
Best Multivitamins -- Caution with Gummies
CL Answer
I have been having dizziness for the past few months and am wondering if it could be a side effect of supplements I take. Which supplements cause dizziness?
Find out which supplements that may cause dizziness, vertigo, or imbalance, including garlic, melatonin, saw palmetto, and red yeast rice.
Product Review
Olive Leaf Extract Supplements Review
Learn What Olive Leaf Does and the Best Brands
Product Review
Lion's Mane and Chaga Supplements Review
Read Labels Carefully -- Many Can Mislead
Product Review
Lavender and Tea Tree Essential Oils Review
Oils Tested for Authenticity and Purity
CL Answer
What are human growth hormone (HGH) supplements? What are the benefits? Are they safe?
Learn about the benefits and risks of human growth hormone (HGH) supplements and injections. Get science-based insights on usage and effects.
CL Answer
Do any supplements or foods help with migraine? Do any trigger migraine?
Find out if supplements such as magnesium, CoQ10, riboflavin, butterbur, feverfew and others help with migraine. Also learn about foods that may trigger migraine, including chocolate and watermelon.
CL Answer
I take omeprazole (Prilosec), a proton pump inhibitor, to reduce stomach acid. Are there supplements I should avoid, or be taking, due to this drug?
Supplement interactions with proton pump inhibitor (PPI) drugs like omeprazole (Prilosec) and Nexium.
Recalls & Warnings
October 05, 2023
Counterfeit Pure Encapsulations and GutConnect 365 Sold on Amazon
On September 26, 2023, a man from New Jersey was arrested for selling fake versions of Pure Encapsulations L-Glutamine and Nature MD's GutConnect 365 on Amazon.
Product Review
L-Theanine Supplements Review
Touted for Stress Relief, Do L-Theanine Supplements Work?
CL Answer
Where to Safely Buy Real Vitamins and Supplements Online, Not Fakes or Counterfeits
ConsumerLab explains how to avoid counterfeit vitamins and supplements when shopping online on Amazon, Walmart.com, and other sites. Learn to identify authorized sites and sellers and avoid fake supplements. Use the brand-by-brand guide to protect yourself from risk.
Product Review
Psyllium Fiber Supplements Review
Find the Best Psyllium Fiber Supplement and Avoid Lead.
CL Answer
Do any supplements help prevent or improve cataracts?
Find out which supplements may help with cataracts, including selenium and vitamins A, B1, B3, C, and E.
CL Answer
Do any supplements reduce the side effects of chemotherapy? Should any be avoided?
Find out if there are any supplements that can help with the side effects of chemotherapy, such as nausea, vomiting, diarrhea, nerve damage and others. ConsumerLab.com's answer explains.
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.
CL Answer
Which supplements, foods or diet and lifestyle changes help relieve acid reflux (heartburn), and which worsen it?
Find out which supplements and foods can help relieve acid reflux, and which can make it worse.
Clinical Update
9/04/2018
Glutamine for IBS?
Glutamine, an amino acid, plays a role in maintaining the digestive tract. Can taking it as a supplement help people with irritable bowel syndrome (IBS)? Find out what a recent study showed in the Glutamine section of the Muscle Enhancers Review.
Clinical Update
6/19/2021
Glutamine and Exercise
Can glutamine supplementation decrease muscle breakdown from exercise? See what a recent study showed in the What It Does section of our Muscle & Workout Supplements Review. Also see our Top Picks among muscle and workout products.
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.
Clinical Update
1/31/2023
What Helps or Worsens Reflux?
Find out if the following improve, or worsen, symptoms of acid reflux:
- Turmeric & Curcumin
- Menthol (in toothpastes, mouthwashes and chewing gum)
- Alanine
- Glutamine
- Glycine
Recalls & Warnings
May 14, 2014
Maker of Mood, Smoking Cessation Supplements and More Warned for Violations, Drug Claims
On April 17, 2014, the FDA issued a warning letter to CDJ Holding, Incorporated, d.b.a.
News Release
November 13, 2006
Tests of "muscle" supplements finds some "weak" products but most contain expected creatine, HMB, or amino acids — Review of muscular enhancement supplements published by ConsumerLab.com
WESTCHESTER, NEW YORK — MONDAY, NOVEMBER 13, 2006 — Bodybuilders and athletes often turn to supplements to enhance muscle size and strength.
Recalls & Warnings
November 14, 2012
Maker of Vitamin C, Aloe and Sexual Enhancement Supplements Warned for Drug Claims and Misbranding
On October 22, 2012, the FDA issued a warning letter to Health Breakthroughs International, LLC after a review of the company's product labels and website found the dietary supplements Amazing C, MPS-Gold 100 and Power Herbal Formula to be promoted as drugs.
Recalls & Warnings
March 05, 2014
Seller of Aloe and Vitamin C Supplements Warned for Manufacturing Violations
On December 12, 2013, the FDA issued a warning letter to Health Breakthroughs International, following a facility inspection which found the company's products, MPS Gold 100, MPS Gold 3X and Amazing C, to be adulterated because they were prepared, packed, or held under conditions that violate ...
News Release
October 20, 2006
ConsumerLab.com report on CoQ10 supplements finds quality high but large range in suggested dosage
WHITE PLAINS, NEW YORK — OCTOBER 20, 2006 — New test results from ConsumerLab.com for CoQ10 supplements show that all of the products selected contained amounts of ingredient consistent with their labels.
Recalls & Warnings
April 11, 2013
Maker of Workout Booster Warned For Manufacturing Violations
On March 5, 2013, the FDA issued a warning letter to Primarch Manufacturing, Inc.
Recalls & Warnings
November 02, 2012
Manufacturer of Prostate, Inflammation and Cholesterol Supplements Warned For Drug Claims
On October 15, 2012, the FDA issued a warning letter to Ortho Molecular Products, Inc. for making drug claims about the following dietary supplements: Candicid Forte, Inflamma-bLOX, Lipitrol, Mucosagen, Prostatrol Forte, Resvoxitrol, Paracid Forte, VascuPak HTN and Lithium Orotate.
News Release
September 24, 2003
Consumerlab.com finds new forms of creatine prone to problems — Test results of muscular enhancement supplements published online today
WHITE PLAINS, NY — September 24, 2003 — Testing by ConsumerLab.com of creatine supplements found problems with the majority of products sold in liquid, effervescent and chewable forms. Problems were not found among standard creatine "powder" products.
News Release
August 28, 2003
Some problems persist with ginseng supplements but overall quality improves according to ConsumerLab.com — Test results published online today
WHITE PLAINS, NY — August 28, 2003 — In contrast to its testing three years ago in which nearly 60% of Asian and American Ginseng supplements were found to have significant problems, testing of recently purchased products by ConsumerLab.
News Release
July 31, 2003
ConsumerLab.com finds many cholesterol-lowering supplements poorly made — Test results published online today
WHITE PLAINS, NY — July 31, 2003 — ConsumerLab.com reported today that more than half of the cholesterol-lowering supplements that it recently purchased failed to contain their listed ingredients and/or could not adequately break apart to release their contents.
News Release
June 10, 2003
ConsumerLab.com finds lead in coral calcium product; Product also charged with false advertising by FTC — Calcium supplement product review published online today
WHITE PLAINS, NY — June 10, 2003 — (Updated August 8) — ConsumerLab.com today reported finding problems among the calcium products recently tested in its Product Review of Calcium Supplements.
News Release
May 20, 2003
Consumers advised to read labels carefully when selecting herbal supplements for prostate — Saw palmetto product review published online today
WHITE PLAINS, NY — May 20, 2003 — ConsumerLab.com reported today that only two-thirds of the saw palmetto supplements it recently evaluated contained ingredients similar to those known to work in clinical studies.
News Release
April 21, 2003
Low quality ingredient appears widespread among Ginkgo supplements according to ConsumerLab.com; points to challenge for FDA's proposed regulations — Review of memory enhancement supplements released today
WHITE PLAINS, NY — April 21, 2003 — In contrast to its findings three years ago, ConsumerLab.com announced today that only 22% of the Ginkgo biloba supplements it recently tested met its quality standards. In late 1999, 75% of the products it tested met these standards.
Recalls & Warnings
February 13, 2013
FDA Warns Maker of Weight Loss and Whey Protein Supplements For Manufacturing Violations and Misbranding
January 25, 2013, the FDA issued a warning letter to dietary supplement manufacturer SciLabs Nutraceuticals, following a facility inspection which found the company's dietary supplements and supplement ingredients, including N-Large 2, Flo-Gard AB, Nitrogen Glutamine capsules, Nutritech nutritional ...
Recalls & Warnings
April 29, 2014
Seller of B Vitamins, CoQ10, Amino Acids and Other Supplements Warned for Manufacturing Violations and Drug Claims
On April 1, 2014, the FDA issued a warning letter to Bio-Recovery, Inc.
Recalls & Warnings
April 16, 2012
Protein Supplement Maker Fails FDA Audit -- Many Products Affected
The FDA sent a Warning Letter (dated April 2, 2012) to Theta Brothers Sports Nutrition, Inc. regarding numerous violations of good manufacturing practices at its Lakewood, New Jersey facility.
Recalls & Warnings
March 04, 2008
Airborne Settles Lawsuit Over False Advertising of its "Miracle Cold Buster"
On March 4, 3008, the Center for Science in the Public Interest (CSPI) announced that the makers of Airborne -- a multivitamin and herbal supplement whose labels and ads falsely claimed that the product cures and prevents colds -- will refund money to consumers who bought the product, as part of a ...
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.
