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L-Lysine 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

  • Generally well tolerated at standard doses
  • GI symptoms (nausea, diarrhea, abdominal cramps) at high doses
  • Theoretical risk of elevated cholesterol with very high chronic intake
  • Rare reports of kidney dysfunction at extreme doses

Drug & Supplement Interactions

  • Aminoglycoside antibiotics — lysine may increase risk of nephrotoxicity
  • Calcium supplements — lysine enhances calcium absorption; monitor total calcium intake
  • Arginine — lysine antagonizes arginine; high doses may reduce arginine-related NO production

Maximum Dose

Do not exceed: 3-6 g/day has been used safely; very high chronic doses may increase cholesterol in rare cases

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References

  1. RCTGriffith RS, Walsh DE, Myrmel KH, et al. (1987). Success of L-lysine therapy in frequently recurrent herpes simplex infection. Dermatologica. DOI PubMed
  2. Civitelli R, Villareal DT, Agnusdei D, et al. (1992). Dietary L-lysine and calcium metabolism in humans. Nutrition. PubMed
  3. RCTSmriga M, Ando T, Akutsu M, et al. (2007). Oral treatment with L-lysine and L-arginine reduces anxiety and basal cortisol levels in healthy humans. Biomedical Research. DOI PubMed
  4. ReviewHayamizu K, Oshima I, Nakano M (2020). Comprehensive Safety Assessment of l-Lysine Supplementation from Clinical Studies: A Systematic Review.. The Journal of nutrition. DOI PubMed
  5. ReviewHayamizu K, Oshima I, Fukuda Z, Kuramochi Y, et al. (2019). Safety assessment of L-lysine oral intake: a systematic review.. Amino acids. DOI PubMed
  6. Meta-analysisFornaro M, Caiazza C, Billeci M, Berk M, et al. (2025). Nutraceuticals and phytoceuticals in the treatment of schizophrenia: a systematic review and network meta-analysis "Nutra NMA SCZ".. Molecular psychiatry. DOI PubMed
  7. Bush JR, Han J, Goodlett DR (2025). Resistant Potato Starch Supplementation Increases Serum Antioxidant Levels in a Randomized Trial.. Metabolites. DOI PubMed
Show 5 more references
  1. Laky B, Huemer D, Eigenschink M, Sagl B, et al. (2024). A Dietary Supplement in the Management of Patients with Lumbar Osteochondrosis: A Randomized, Double-Blinded, Placebo-Controlled Study.. Nutrients. DOI PubMed
  2. Shen S, Liu X, Huang J, Sun Y, et al. (2024). Efficacy of a mouthwash containing ε-poly-L-lysine, funme peptides and domiphen in reducing halitosis and supragingival plaque: a randomized clinical trial.. BMC oral health. DOI PubMed
  3. Schön C, Micka A, Gourineni V, Bosi R (2024). Superior bioavailability of EPA and DHA from a L-lysine salt formulation: a randomized, three-way crossover study.. Food & nutrition research. DOI PubMed
  4. Tsikas D, Maassen N, Thorns A, Finkel A, et al. (2022). Short-Term Supplementation of Sodium Nitrate vs. Sodium Chloride Increases Homoarginine Synthesis in Young Men Independent of Exercise.. International journal of molecular sciences. DOI PubMed
  5. Hong J, Kim HS, Do S, Kim HJ, et al. (2021). Effects of Lysine Cell Mass Supplementation as a Substitute for L-Lysine·HCl on Growth Performance, Diarrhea Incidence, and Blood Profiles in Weaning Pigs.. Animals : an open access journal from MDPI. DOI PubMed