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L-Glutamine Side Effects & Safety

Evidence:Moderate
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This content is for informational purposes only and does not constitute medical advice. Statements about dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease. Individual results may vary — consult your healthcare provider before starting any supplement. Full disclaimer

Safety Profile

Overall safety rating: Generally Safe

Potential Side Effects

  • Very well tolerated at standard doses
  • Mild GI discomfort at very high doses (>20 g)
  • Theoretical concern about glutamate conversion in neurological conditions

Drug & Supplement Interactions

  • Lactulose — glutamine may reduce lactulose efficacy for hepatic encephalopathy
  • Anti-seizure medications — theoretical concern about glutamate excitotoxicity
  • Chemotherapy — consult oncologist before use

Maximum Dose

Do not exceed: 40 g/day has been used in clinical settings; 20 g/day is a typical upper dose for supplements

Full L-Glutamine Guide

References

  1. ReviewCieri-Hutcherson NE, Hutcherson TC, Conway-Habes EE, Burns BN, et al. (2019). Systematic Review of l-glutamine for Prevention of Vaso-occlusive Pain Crisis in Patients with Sickle Cell Disease.. Pharmacotherapy. DOI PubMed
  2. RCTHassanein FEA, Mikhail C, Elkot S, Abou-Bakr A (2025). L-arginine vs. L-glutamine oral suspensions for radiation-induced oral mucositis: a triple-blind randomized trial.. Journal of cancer research and clinical oncology. DOI PubMed
  3. RCTLu TL, Zheng AC, Suzuki K, Lu CC, et al. (2024). Supplementation of L-glutamine enhanced mucosal immunity and improved hormonal status of combat-sport athletes.. Journal of the International Society of Sports Nutrition. DOI PubMed
  4. Bloomer RJ, Pence J, Hellenbrand J, Davis A, et al. (2024). Randomized Trial to Assess the Safety and Tolerability of Daily Intake of an Allulose Amino Acid-Based Hydration Beverage in Men and Women.. Nutrients. DOI PubMed
  5. RCTTsujimoto T, Wasa M, Inohara H, Ito T (2023). L-Glutamine and Survival of Patients with Locally Advanced Head and Neck Cancer Receiving Chemoradiotherapy.. Nutrients. DOI PubMed
  6. ObservationalPavel FM, Bungau SG, Tit DM, Ghitea TC, et al. (2023). Clinical Implications of Dietary Probiotic Supplement (Associated with L-Glutamine and Biotin) in Ulcerative Colitis Patients' Body Composition and Quality of Life.. Nutrients. DOI PubMed
  7. Adiamah A, Skorepa P, Weimann A, Lobo DN (2024). Effects of preoperative beta-hydroxy-beta-methylbutyrate, arginine, and glutamine supplementation on outcomes.. Journal of parenteral and enteral nutrition. DOI PubMed
Show 2 more references
  1. Weimann A, Braga M, et al. (2024). Impact of preoperative beta-hydroxy-beta-methylbutyrate, arginine, and glutamine on outcomes.. Clinical nutrition ESPEN. DOI PubMed
  2. Tepaske R, et al. (2022). Evaluation of the recovery after heart surgery following preoperative supplementation with glutamine, arginine, and omega-3 fatty acids.. Nutrition. DOI PubMed