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Glycine 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

  • Extremely well tolerated
  • Mild GI discomfort at very high doses (>15 g)
  • Has a pleasant sweet taste

Drug & Supplement Interactions

  • Clozapine — glycine is studied as an adjunct for schizophrenia but may interact with antipsychotics
  • No significant negative interactions at standard doses

Maximum Dose

Do not exceed: 10 g/day has been used safely; glycine has a very high safety margin

Full Glycine Guide

References

  1. RCTYamadera W, Inagawa K, Chiba S, et al. (2007). Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. Sleep and Biological Rhythms. DOI
  2. RCTSekhar RV, Patel SG, Guthikonda AP, et al. (2011). Deficient synthesis of glutathione underlies oxidative stress in aging and can be corrected by dietary cysteine and glycine supplementation. American Journal of Clinical Nutrition. DOI PubMed
  3. Błaszczuk A, Barańska A, Kanadys W, Malm M, et al. (2022). Role of Phytoestrogen-Rich Bioactive Substances (Linum usitatissimum L., Glycine max L., Trifolium pratense L.) in Cardiovascular Disease Prevention in Postmenopausal Women: A Systematic Review and Meta-Analysis.. Nutrients. DOI PubMed
  4. Meta-analysisWittemans LBL, Lotta LA, Oliver-Williams C, Stewart ID, et al. (2019). Assessing the causal association of glycine with risk of cardio-metabolic diseases.. Nature communications. DOI PubMed
  5. Jia Q, Han Y, Huang P, Woodward NC, et al. (2019). Genetic Determinants of Circulating Glycine Levels and Risk of Coronary Artery Disease.. Journal of the American Heart Association. DOI PubMed
  6. Van K, McHale LK (2017). Meta-Analyses of QTLs Associated with Protein and Oil Contents and Compositions in Soybean [Glycine max (L.) Merr.] Seed.. International journal of molecular sciences. DOI PubMed
  7. Siegert W, Ahmadi H, Rodehutscord M (2015). Meta-analysis of the influence of dietary glycine and serine, with consideration of methionine and cysteine, on growth and feed conversion of broilers.. Poultry science. DOI PubMed
Show 4 more references
  1. Dorne JL, Walton K, Renwick AG (2004). Human variability for metabolic pathways with limited data (CYP2A6, CYP2C9, CYP2E1, ADH, esterases, glycine and sulphate conjugation).. Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association. DOI PubMed
  2. (1991). Impact of glycine-containing ORS solutions on stool output and duration of diarrhoea: a meta-analysis of seven clinical trials. The International Study Group on Improved ORS.. Bulletin of the World Health Organization. PubMed
  3. Guasp M, Saiz A, Ruiz-Vives M, Almendrote M, et al. (2025). Progressive Encephalomyelitis With Rigidity and Myoclonus With Glycine Receptor Antibodies: Clinical Features and Outcomes.. Neurology(R) neuroimmunology & neuroinflammation. DOI PubMed
  4. ReviewSoh J, Raventhiran S, Lee JH, Lim ZX, et al. (2024). The effect of glycine administration on the characteristics of physiological systems in human adults: A systematic review.. GeroScience. DOI PubMed