What the evidence says. Graded mixed: glutamine is a genuine, FDA-approved drug for sickle cell disease, but for the way it is actually marketed — muscle recovery, immunity, and 'leaky gut' in healthy people — meta-analyses are largely null, and high-dose IV glutamine increased mortality in critically ill patients. (Mixed evidence: Conflicting results across studies; benefit uncertain.)
What is Glutamine?
Glutamine (L-Glutamine) is a performance supplement used for reduces sickle cell pain crises (rx). NutriDex grades the human evidence as Mixed. Glutamine is the most abundant free amino acid in the body and a fuel for gut and immune cells, which drives its supplement marketing. The evidence splits sharply. Pharmaceutical L-glutamine (Endari) is FDA-approved for sickle cell disease, where a phase-3 RCT cut pain crises ~25% and hospitalizations ~33%. In surgery, meta-analyses show fewer infections and shorter stays. But for popular fitness and wellness claims the data are weak: a meta-analysis of athletes found no effect on immune markers, VO2max or body composition, and high doses reduced intestinal permeability only modestly during heat-stress running. High-dose intravenous glutamine actually increased mortality in critically ill patients (REDOXS). Healthy, well-fed people make plenty of their own glutamine, so routine supplementation for recovery or 'gut healing' has little proven benefit. The clinical value is real but narrow and prescription-bound.
Purported Benefits
✓Reduces sickle cell pain crises (Rx)
✓May lower exercise gut permeability
✓Post-surgical immune support
✓Modest eccentric-exercise recovery
Evidence by outcome
The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.
Oral glutamine is well tolerated up to ~30 g/day; mild bloating, nausea or constipation can occur. Avoid in people with cirrhosis or hepatic encephalopathy, since glutamine raises ammonia. Do not assume IV/high-dose safety: in the REDOXS trial high-dose intravenous glutamine increased mortality in critically ill patients with renal or multi-organ failure. It may blunt some anti-seizure and chemotherapy effects and can lower the lactulose used as a laxative/ammonia treatment; discuss with a clinician if you take antiepileptics, are on cancer therapy, or have kidney or liver disease. Educational only — always check with your doctor or pharmacist before combining Glutamine with any medicine.
Glutamine is most often taken for Reduces sickle cell pain crises (Rx), May lower exercise gut permeability, Post-surgical immune support, Modest eccentric-exercise recovery. Abundant amino acid sold for gut, immunity and recovery.
Does Glutamine work — what does the evidence say?
Mixed evidence. Conflicting results across studies; benefit uncertain. Glutamine is the most abundant free amino acid in the body and a fuel for gut and immune cells, which drives its supplement marketing. The evidence splits sharply. Pharmaceutical L-glutamine (Endari) is FDA-approved for sickle cell disease, where a phase-3 RCT cut pain crises ~25% and hospitalizations ~33%. In surgery, meta-analyses show fewer infections and shorter stays. But for popular fitness and wellness claims the data are weak: a meta-analysis of athletes found no effect on immune markers, VO2max or body composition, and high doses reduced intestinal permeability only modestly during heat-stress running. High-dose intravenous glutamine actually increased mortality in critically ill patients (REDOXS). Healthy, well-fed people make plenty of their own glutamine, so routine supplementation for recovery or 'gut healing' has little proven benefit. The clinical value is real but narrow and prescription-bound.
What is the typical dose of Glutamine?
Recovery/gut studies use 0.1–0.3 g/kg (roughly 5–30 g/day); the FDA-approved sickle-cell drug Endari is 0.3 g/kg twice daily.
Is Glutamine safe? Any cautions or side effects?
Oral glutamine is well tolerated up to ~30 g/day; mild bloating, nausea or constipation can occur. Avoid in people with cirrhosis or hepatic encephalopathy, since glutamine raises ammonia. Do not assume IV/high-dose safety: in the REDOXS trial high-dose intravenous glutamine increased mortality in critically ill patients with renal or multi-organ failure. It may blunt some anti-seizure and chemotherapy effects and can lower the lactulose used as a laxative/ammonia treatment; discuss with a clinician if you take antiepileptics, are on cancer therapy, or have kidney or liver disease.
How many studies support Glutamine?
NutriDex cites 9 sources for Glutamine, graded "Mixed".
Cite this page
APA
Peh, D. (2026). Glutamine (L-Glutamine): Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 16 Sept 2026, from https://nutridex.info/s/l-glutamine
BibTeX
@misc{nutridex_l_glutamine,
author = {Peh, Daryl},
title = {Glutamine (L-Glutamine): Benefits, Dosage, Side Effects \& Evidence},
year = {2026},
howpublished = {NutriDex --- The Supplement Research Compendium},
url = {https://nutridex.info/s/l-glutamine},
note = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-09-16}
}
For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.