An essential amino acid and cheap supplement, best known for cold sores, where any effect is modest and depends on dose plus cutting back arginine-rich foods. Weaker signals exist for stress and bone, mainly in people who eat little lysine. Generally well tolerated; no link to longer life. (Full Review)

Protocol

Preventive Dose

1 g/day L-lysine

Ongoing prophylaxis for recurrent cold sores; benefit emerges around and above 1 g/day.

Active Outbreak

3 g/day, divided

Raised at first sign of outbreak (tingling/prodrome) for a short period, split into 2–3 doses.

Arginine Restriction

Limit nuts, seeds, chocolate

Temporarily reduced-arginine diet maximizes the lysine-to-arginine ratio; an alternative emphasis, not universally required.

Time to effect

Outbreak Prevention

Several weeks

Consistent daily dosing needed before any reduction in outbreak frequency can be judged.

Active Outbreak Healing

Days

Higher-dose lysine started at first tingling; healing assessed over days.

Benefits

Medium: Reduced recurrent cold sore frequency and severity

Low: Reduced anxiety and stress-hormone levels; improved calcium absorption and bone support; support of collagen formation and wound healing

Speculative: Preservation of muscle mass with aging; general longevity effects

Contraindications

Kidney disease (including significantly reduced eGFR)

Glutaric aciduria type I

Gallstones or gallbladder disease

Pregnancy or breastfeeding

Key Interactions

Calcium supplements

Arginine-containing supplements

Aminoglycoside antibiotics (e.g., gentamicin, tobramycin)

Cardiovascular disease

Risk & Side Effects

Medium: Gastrointestinal upset

Low: Renal strain at high or prolonged doses; disrupted calcium balance when combined with calcium supplements

Speculative: Cardiovascular or gallbladder concerns; theoretical atherogenesis from chronic high dosing

Monitoring

Marker	Target	Why
Serum creatinine	~0.6–1.0 mg/dL	Detects kidney strain from high amino-acid load
eGFR	>90 mL/min/1.73m²	Confirms adequate kidney filtration before/during high-dose use
Serum calcium	9.2–10.0 mg/dL	Catches excess blood calcium when lysine is combined with calcium intake
Blood urea nitrogen (BUN)	10–18 mg/dL	Reflects protein/amino-acid handling and hydration

Cadence: Baseline before sustained higher-dose use; recheck kidney function and blood calcium every 6–12 months on prolonged multi-gram dosing, and sooner if symptoms arise.

Qualitative Assessment

Cold-sore outbreak frequency, size, and healing time
Subjective anxiety and stress levels (most relevant for low-lysine individuals)
Gastrointestinal tolerability (nausea, cramping, loose stools) as a dose-limiting signal
General energy and well-being

Lysine for Health & Longevity

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment