L-Lysine

Lysine

Snapshot

Indications	Contraindications
Childhood growth support¹ Nitrogen retention¹ Genital herpes self-management² Salt-sensitive hypertension³	Glutaric aciduria type I⁴ Hyperlysinemia⁵

L-lysine is an essential amino acid used for protein synthesis, collagen crosslinking, mineral absorption, and carnitine production⁵. Supplementation supplies lysine where the diet is short of it, as in cereal-based diets, and is used for childhood growth and nitrogen retention¹. People also take it for herpes outbreaks and for stress and anxiety, where trials are few. The typical patient is a child or adolescent eating cereal staples.

Evidence is clearest for growth: a review of supplementation and lysine-fortified cereal diets in children reported better nitrogen retention and anthropometric measures¹. In salt-sensitive hypertension, animal and pilot human work points to kidney protection, and the authors state further clinical research is needed³. In 2021, a survey of members of a British herpes patient association found a diet with reduced arginine and increased lysine among the most frequent alternative treatments. Products listing L-lysine are mostly capsules, tablets, and powders; see Form comparison.

Health Canada labels ask for a practitioner's advice before use in pregnancy⁶ or on a low-protein diet⁶. Inherited defects of lysine catabolism lead the cautions because lysine restriction is a key therapy in glutaric aciduria type I⁴.

Last updated October 16, 2026. Read how we make monographs.

In the full monograph

62 sources, 42 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources