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Supplement Forms/Alternate Names:

L-lysine, lysine hydrochloride


Lysine is an essential compound in the body. It is found in meat, dairy, eggs, and beans. Lysine has been used to prevent cold sores and genital herpes. It can be taken as a pill or power. It can also be applied to the skin.


3 to 6 grams daily

What Research Shows

May Be Effective

  • Schizophrenia —may improve symptoms when used with standard treatment D1

Not Enough Data to Assess

  • Anxiety A1
  • Cold sores B1

Editorial process and description of evidence categories can be found at EBSCO NAT Editorial Process.

Safety Notes

It is likely safe to take lysine in small doses for a short time, but stomach upset and diarrhea may happen.C1 Not enough studies have been done to say whether it is safe to take for a long period or by women who are pregnant or breastfeeding.


Talk to your doctor about any supplements or therapy you would like to use. Some can interfere with treatment or make conditions worse.



A. Anxiety

A1. Lakhan SE, Vieira KF. Nutritional and herbal supplements for anxiety and anxiety-related disorders: systematic review. Nutr J. 2010;9:42.

B. Cold Sores

B1. Chi CC, Wang SH, et al. Interventions for prevention of herpes simplex labialis (cold cores on the lips). Cochrane Database Syst Rev. 2015;(8):CD010095.

C. Safety

C1. Hayamizu K, Oshima I, et al. Safety assessment of L-lysine oral intake: a systematic review. Amino Acids. 2019 Apr;51(4):647-659.

D. Schizophrenia

D1. Zeinoddini A, Ahadi M, et al. L-lysine as an adjunct to risperidone in patients with chronic schizophrenia: a double-blind, placebo-controlled, randomized trial. J Psychiatr Res. 2014;59:125-131.

Last reviewed March 2020 by EBSCO NAT Review Board Eric Hurwitz, DC  Last Updated: 6/22/2020