Lysine
TL;DR
Essential amino acid that the body cannot produce - must come from diet or supplements
Best evidence is for reducing cold sore frequency and severity
Competes with arginine - herpes virus needs arginine to replicate
Supports collagen production and bone health through calcium absorption
Very safe and affordable with minimal side effects
Best for: cold sore prevention, general protein needs
What it is
L-lysine is one of nine essential amino acids that the body cannot synthesize and must obtain from food or supplements. It's crucial for protein synthesis, collagen formation, carnitine production, and immune function. Lysine is particularly abundant in animal proteins, legumes, and dairy products.
The most well-researched use of lysine supplements is for managing herpes simplex virus (HSV) infections, particularly cold sores. The mechanism involves lysine competing with arginine, another amino acid that the herpes virus requires for replication.
What the research says
Lysine on Amazon
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Safety
Lysine is very safe for most people at typical supplement doses of 1-3g daily. It's a natural component of dietary protein, so toxicity is unlikely. Higher doses (above 3g daily) may cause gastrointestinal upset, including nausea and diarrhea.
Very high doses (above 10g daily) have been associated with kidney problems in animal studies, but this level is far above typical supplement use. People with kidney disease should consult a healthcare provider before using lysine supplements.
Interactions
• Arginine supplements - Lysine competes with arginine for absorption and cellular uptake • Calcium absorption - May enhance calcium absorption, potentially beneficial for bone health • Minimal drug interactions - Generally considered safe with medications
Dosing
Cold Sore Prevention 1-3g daily in divided doses, taken consistently. Some people take higher doses (up to 3g) at the first sign of an outbreak.
General Health/Protein Support 500-1000mg daily. This supplements dietary lysine intake, especially for those with limited animal protein consumption.
Timing Take on an empty stomach for better absorption, or with meals if GI upset occurs. Avoid taking with arginine supplements.
Cost
Lysine is one of the most affordable amino acid supplements available. A month's supply typically costs $8-15, with powder forms being slightly more economical than capsules. The low cost makes it accessible for long-term use in cold sore prevention protocols.
The bottom line
Lysine has solid evidence for reducing cold sore outbreaks and is worth trying if you're prone to HSV-1 infections. The mechanism makes biological sense, it's very safe, and it's cheap enough to use long-term. For other uses like bone health or general protein support, the evidence is weaker, but lysine remains a reasonable addition to a comprehensive amino acid or protein supplementation plan.
References
- Civitelli R, Villareal DT, Agnusdei D, et al. Dietary L-lysine and calcium metabolism in humans. Nutrition. 1992;8(6):400-5.
- Griffith RS, Walsh DE, Myrmel KH, et al. Success of L-lysine therapy in frequently recurrent herpes simplex infection. Treatment and prophylaxis. Dermatologica. 1987;175(4):183-90.
Sources for this page include published meta-analyses, systematic reviews, and NIH dietary supplement fact sheets. All claims reflect the evidence as of early 2026.
This is not medical advice. Consult your healthcare provider before starting any supplement, especially if you take medications.