Quick Summary
What is L-glutamine?
Glutamine (L-glutamine) is an amino acid that your body produces. It is involved in cellular energy production and plays a role in maintaining muscle cells, the immune system, and the digestive tract.(See details in What It Is).
What are the health benefits of L-glutamine?
Although you do not need to get glutamine from your diet or supplement with it, there is some evidence that large doses (several grams) may reduce infections after over-training, reduce symptoms of irritable bowel syndrome after infections, and reduce mouth irritation due to chemotherapy (see details in What It Does).
How much L-glutamine is taken?
Typical dosage of L-glutamine is 4 to 6 grams (4,000 to 6,000 mg) taken one or more times daily (see details in ConsumerTips).
Which L-glutamine supplement is best?
Nearly all L-glutamine supplements contain essentially the same L-glutamine in its free form. However, the cost can range from just 4 cents to 56 cents per gram. Among products Approved for quality in ConsumerLab ’s tests of popular L-glutamine supplements (see What CL Found and How Products Were Evaluated), ConsumerLab selected a Top Pick for L-glutamine powder and a Top Pick for L-glutamine capsules, each of which represent exceptional value relative to other products.
What to look for on L-glutamine labels?
L-glutamine is sold almost exclusively in the free form and is produced by fermentation, so it is not necessary to pay more for products claiming to be “free form.”
L-glutamine safety and side effects:
Glutamine is believed to be generally safe but can cause gastrointestinal side effects at daily doses of 10 grams or more. Lower doses may cause symptoms in people hypersensitive to MSG (monosodium glutamate). Dry mouth, headache, and dizziness may occur with daily doses of 30 grams or more. There is concern glutamine may interfere with anti-epilepsy drugs and may trigger mania in people with bipolar disorder. (See details in Concerns and Cautions).
Also see our Review of Muscle & Workout Supplements (Creatine and Branched-chain Amino Acids).
Products tested in 2025
+— 20 sources
In addition the results of its expert testing, ConsumerLab uses only high-quality, evidence based, information sources. These sources include peer-reviewed studies and information from agencies such as the FDA and USDA, and the National Academy of Medicine. On evolving topics, studies from pre-print journals may be sourced. All of our content is reviewed by medical doctors and doctoral-level experts in pharmacology, toxicology, and chemistry. We continually update and medically review our information to keep our content trustworthy, accurate, and reliable. The following sources are referenced in this article:
- Cruzat, Nutrients 2018
- Isao, J Nutr 2001
- Castell, Eur J Appl Physiol Occup Physiol 1996
- Cordova-Martinez, Nutrients 2021
- Hond, Aliment Pharmacol Ther 1999
- Lopez-Vaquero, Mol Clin Oncol 2017
- Peterson, Cancer 2006
- Tsujimoto, Oncol Rep 2015
- Walsh, Sports Med 1998
- Zhou, Gut 2018
- Gowda, Anal Chem 2014
- Weiss, BMC Biophysics 2018
- Bhoelan, Nephron 2025
- Brandley, Front Psychiatry 2022
- Chapman, J Nutr 2000
- FDA 2018
- Laviano, Eur J Clin Nutrition 2014
- Mebane, Am J Psychiatry 1984
- Nutrastore Prescribing Information 2004
- Ogden, Nutrients 2020
You must
be a member to get the full test results along with ConsumerLab.com recommendations and quality ratings. You will get results for 7 L-glutamine supplements selected for testing by ConsumerLab, as well as one additional product (indicated with a CL flask) that was tested at the request of its distributor through CL's voluntary
Quality Certification Program.
In this comprehensive review, you'll discover:
Which L-glutamine supplements passed or failed testing- Which L-glutamine supplements offer the best quality and value and are CL's Top Picks
- If L-glutamine supplement labels are accurate
- What it really means if an L-glutamine supplement is or is not labeled as containing the "free form" of glutamine
- The health benefits of L-glutamine, and if it can help to boost the immune system, improve exercise performance, or protect the stomach from NSAIDS
- What to look for when choosing an L-glutamine supplement and the best way to take and store L-glutamine supplements
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