L-Lysine
Supplements · Amino Acids · Supplement, Typed Supps
A building-block protein your body needs, sold mainly as a cold sore remedy — though the proof is shaky.
Stage by stage
- Intake (Capsule): Absorbed efficiently in the small intestine.
- Small intestine (Efficient absorption): Absorbed alongside standard digestion.
- Bloodstream (Circulates): Carried through the blood to tissues throughout the body.
- Viral replication balance (Studied for cold sores): Thought to work partly by shifting the arginine-to-lysine ratio that the herpes simplex virus depends on to replicate.
What the evidence supports
- Preventing or reducing recurrence of cold sores (herpes labialis) — insufficient evidence. Trials are contradictory and the better-designed placebo-controlled studies found no effect on recurrence; no major guideline recommends it. A popular claim that has largely failed when tested.
- Evidence on Long-term safety of high daily doses — limited evidence. Up to about 3 g per day is generally regarded as safe, but long-term high-dose data are thin, which is why caution is advised in kidney or liver disease.
Typical dose
1-3 g daily for prophylaxis, or up to 3 g daily during an outbreak — the most-studied range, though efficacy is unproven
Upper limit: No established upper limit; up to about 3 g daily is generally considered safe
Timing
With food; some take it preventively, others at the first sign of a cold sore.
Time to effect
- Days: Any reported reduction in cold sore frequency or duration in studies.
Common myth
“Lysine cures cold sores.” In reality: Evidence suggests a modest effect on frequency and healing time for some people — not a cure, and evidence quality varies across studies.
Food sources
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