Amino Acid ·Moderate evidence ·Reviewed May 2026
Essential amino acid important for collagen synthesis, calcium absorption, and antiviral activity.
The bottom line
Evidence rating moderate. Most-documented uses: cold sore prevention, collagen synthesis, calcium absorption. 16 sources indexed (1984–2026), with 6 interaction records on file.
Core mechanism
Required for collagen cross-linking (hydroxylysine). Competes with arginine for cellular uptake, inhibiting HSV replication. Supports carnitine synthesis and calcium absorption.12,7
Ranked by evidence and value.
Real-world pricing across three quality tiers. Assumes L-Lysine HCl.
Assumes 500-3,000 mg/day. Vendor basis: NOW/iHerb, Vitacost, BulkSupplements powder, and Amazon marketplace; powder is the budget tier. Updated 2026-05-28.
How much you'd eat to match a supplemental dose.
Whole proteins are usually a practical lysine source.
What to test, the optimal window inside the conventional range, and how long a response takes.
L-lysine (500 to 3000 mg per day) raises plasma lysine; clinical use is primarily for HSV outbreak prevention (modest RCT support).10,11
Lysine and arginine compete for cellular uptake; HSV mechanism is thought to involve shifting the arginine/lysine ratio.
Where this appears in the symptom-to-supplement map, ranked by relevance.
L-lysine shifts the lysine to arginine ratio, modestly reducing HSV outbreak frequency in long-term users.7,1
Reduce dietary arginine sources (nuts, chocolate) during outbreaks for additive effect.
L-lysine competes with arginine, an amino acid the varicella zoster virus uses to replicate, and may modestly support control of herpesvirus reactivation.7,13
Strictly adjunctive: the lysine-arginine data come mostly from cold sores (HSV), not zoster (VZV), so it does not replace the prescribed antiviral. Seek medical care within 72 hours of the rash appearing, when antivirals work best.
Lysine is sometimes used for oral lesions and may have a role in tissue repair, though evidence for canker sores specifically is limited.
Better supported for herpes cold sores than for true aphthous ulcers, so set expectations accordingly.
Arginine and lysine compete for cellular uptake; high-dose arginine can reduce lysine's effect on HSV outbreak prevention.
Recommendation: Separate by 2 hours and avoid high-dose arginine during active HSV outbreaks. Reduce dietary arginine sources (nuts, chocolate) when using lysine for HSV.
L-lysine can enhance intestinal calcium absorption and reduce urinary calcium excretion, supporting calcium retention.
Recommendation: Can be taken together; lysine may improve the efficiency of calcium uptake when bone or calcium support is the goal.
Adding L-lysine alongside iron has been associated with improved ferritin levels in some iron-deficient individuals who do not fully respond to iron supplementation alone.
Recommendation: Lysine may be a useful adjunct alongside iron in poor responders; continue standard iron dosing and monitor ferritin.
Lysine is a key amino acid in collagen and, in its hydroxylated form, is required for the cross-links that give collagen tensile strength, complementing collagen peptide supplementation.
Recommendation: Can be taken together to support collagen-related goals; ensure adequate vitamin C as well for the hydroxylation step.
L-lysine is used by some patients as adjunctive prophylaxis against herpes simplex recurrences, working by a different mechanism than acyclovir. Evidence is mixed and modest, but daily doses above 1-3 g have shown subjective benefit in some trials, with no known pharmacokinetic interaction with acyclovir or valacyclovir.
Recommendation: Lysine is reasonable as a complement to acyclovir for recurrent oral or genital HSV, typically at 1-3 g per day. Do not use it as a substitute for prescribed antivirals during an active outbreak.
Valacyclovir is the prodrug of acyclovir, and L-lysine prophylaxis works through a separate, arginine-competition mechanism against HSV. Evidence is modest and best supported for daily doses above 1 g, but there is no known pharmacokinetic interaction with valacyclovir, and combination use is reasonable for recurrence prevention.
Recommendation: Lysine 1-3 g/day is a reasonable adjunct to valacyclovir for recurrent HSV. Continue valacyclovir as prescribed during active outbreaks; do not rely on lysine alone.
Numbered references. Citations throughout the page link here.
Aymerich P, Tokach MD, Dritz SS et al.. Lysine requirements of finishing boars and gilts: A meta-analysis. Animal : an international journal of animal bioscience. 2021
Montroy J, Fergusson NA, Hutton B et al.. The Safety and Efficacy of Lysine Analogues in Cancer Patients: A Systematic Review and Meta-Analysis. Transfusion medicine reviews. 2017
Vyas D, Erdman RA. Meta-analysis of milk protein yield responses to lysine and methionine supplementation. Journal of dairy science. 2009
van Lieshout GAA, Trommelen J, Hendriks FK et al.. Milk Protein Glycation Compromises Postprandial Lysine Bioavailability but does not Modulate Postprandial Muscle Protein Synthesis Rates In Vivo in Males: A Double-blind, Randomized Parallel Trial. The Journal of nutrition. 2025
L-lysine significantly increased intestinal calcium absorption and improved renal conservation of absorbed calcium, suggesting usefulness for osteoporosis prevention.
When serum lysine concentration exceeded 165 nmol/ml there was a significant decrease in HSV recurrence rate, suggesting prophylactic benefit at adequate serum levels.
Hashim M, Alam I, Ahmad M et al.. Comprehensive Review of L-Lysine: Chemistry, Occurrence, and Physiological Roles. Current protein & peptide science. 2026
Han D, Lu J, Fan B et al.. Lysine-Specific Demethylase 1 Inhibitors: A Comprehensive Review Utilizing Computer-Aided Drug Design Technologies. Molecules (Basel, Switzerland). 2024
Pedrazini MC, da Silva MH, Groppo FC. L-lysine: Its antagonism with L-arginine in controlling viral infection. Narrative literature review. British journal of clinical pharmacology. 2022
L-lysine supplements are clinically safe with no reported toxicity; adverse events limited to subjective GI symptoms. NOAEL is 6000 mg/person/day.
Lysine along with protein and vitamin D play critical roles in muscle and bone health; lysine is essential for collagen cross-linking and calcium absorption.
L-lysine supplementation appears to be ineffective for HSV prophylaxis at doses less than 1 g/day without low-arginine diet; higher doses with dietary modification may be beneficial.
Review of 71 articles (3357 subjects) with doses up to 17.5 g/day found L-lysine safe with gastrointestinal symptoms as only side effects; provisional NOAEL of 6000 mg/day.
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