Lysine
Useful mainly for people with recurrent oral or genital herpes wanting to reduce outbreak frequency.
Quick decision guide
May help most
people with recurrent oral or genital herpes wanting to reduce outbreak frequency
Common dosing range
1–3 g/day for suppression; 3–6 g/day during outbreaks
When to expect effects
Weeks for suppression
Watch out for
People with chronic kidney disease should consult a clinician before supplementing
What is it
Is it worth it for you?
Use this as a quick fit check, not a diagnosis.
Worth considering if…
Probably skip if…
Evidence at a glance
| Goal | Effect | Best fit | Time |
|---|---|---|---|
anxiety reduction Limited Evidence | Small | people with low dietary lysine, often studied combined with arginine | Weeks |
herpes simplex prevention and treatment Mixed Evidence | Modest reduction in outbreak frequency and severity | people with recurrent HSV-1 (cold sores) or HSV-2 outbreaks | Weeks |
anxiety reduction
- Effect
- Small
- Best fit
- people with low dietary lysine, often studied combined with arginine
- Time
- Weeks
herpes simplex prevention and treatment
- Effect
- Modest reduction in outbreak frequency and severity
- Best fit
- people with recurrent HSV-1 (cold sores) or HSV-2 outbreaks
- Time
- Weeks
Evidence for 2 uses
AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.
anxiety reduction
Supplement benefitSome trials, several using lysine plus arginine, report reduced anxiety and stress responses, partly in populations with low lysine intake. Evidence is limited and often confounded by the combination used.
Bottom line: Lysine may modestly reduce anxiety in some settings, but evidence is preliminary.
herpes simplex prevention and treatment
Supplement benefitTrials of 1–3 g/day lysine report fewer and less severe herpes outbreaks, plausibly because lysine limits arginine availability that HSV needs to replicate. Effect sizes are modest and trial quality is mixed, so confidence remains limited.
Bottom line: Lysine modestly reduces herpes outbreak frequency and severity but does not cure infection.
Evidence is mixed
Some controlled trials show benefit while others show little effect; doses and outcome measures vary.
How it works
How to take it
What to track
3 commercial forms
Compare the main delivery options and what they’re best suited for.
L-lysine HCl
The most common consumer form, available as capsules, tablets, or powder. Affordable and well-studied for herpes prevention.
Hydrochloride salt; well absorbed orally.
L-lysine monohydrate
Alternative salt form with similar effects.
Equally well absorbed as HCl form.
Lysine + vitamin C combinations
Marketed for skin, joint, and collagen support. The combination is biochemically rational but not proven to outperform either alone.
Vitamin C supports collagen synthesis where lysine is a key residue.
Safety
Know the common side effects, key cautions, and who should avoid it.
Common side effects
Serious risks
possible worsening of renal function in chronic kidney disease
kidney stones at very high chronic intake
Who should avoid it
- people with chronic kidney disease (consult clinician)
- people with lysinuric protein intolerance
- people with hypercalcemia on high-dose calcium
Pregnancy & breastfeeding
Pregnant and breastfeeding women should rely on dietary intake rather than supplements.
Interactions
lysine may increase calcium absorption, a theoretical hypercalcemia risk
competes for intestinal absorption; separate by several hours
Food sources
| Food | Amount | %DV |
|---|---|---|
| Beef (3 oz) | ~2.4 g | — |
| Chicken breast (3 oz) | ~2.5 g | — |
| Salmon (3 oz) | ~2 g | — |
| Cottage cheese (1 cup) | ~2.2 g | — |
| Eggs (1 large) | ~0.5 g | — |
| Tempeh (1/2 cup) | ~0.9 g | — |
| Lentils (1 cup cooked) | ~1.2 g | — |
| Greek yogurt (1 cup) | ~1.7 g | — |
Beef (3 oz)
- Amount
- ~2.4 g
- %DV
- —
Chicken breast (3 oz)
- Amount
- ~2.5 g
- %DV
- —
Salmon (3 oz)
- Amount
- ~2 g
- %DV
- —
Cottage cheese (1 cup)
- Amount
- ~2.2 g
- %DV
- —
Eggs (1 large)
- Amount
- ~0.5 g
- %DV
- —
Tempeh (1/2 cup)
- Amount
- ~0.9 g
- %DV
- —
Lentils (1 cup cooked)
- Amount
- ~1.2 g
- %DV
- —
Greek yogurt (1 cup)
- Amount
- ~1.7 g
- %DV
- —
Choosing a product
What to look for on the label — and what to be skeptical of.
Look for…
Be skeptical of…
Frequently asked questions
Does lysine actually prevent cold sores?⌄
Probably modestly. Multiple older trials showed reduced outbreak frequency at 1 to 3 g/day. Effects aren't dramatic and won't replace antiviral medication for severe outbreaks, but as a low-cost daily supplement it has a plausible mechanism and reasonable evidence.
Can I take lysine and arginine together?⌄
Yes, but separate them by several hours because they compete for the same intestinal transporter. If your goal is arginine effects (NO production), don't take lysine close to it.
How much lysine is in a typical diet?⌄
Adults eating roughly 70 grams of protein per day, including animal sources, easily exceed the 38 mg/kg/day RDA. Plant-based diets centered on grains (which are low in lysine) and legumes (which are higher) are mostly adequate if the foods are varied.
Is lysine safe long-term?⌄
At doses up to 3 g/day for months, lysine appears well tolerated. Chronic doses above 6 g/day have not been well studied, and very high doses may stress the kidneys. People with kidney disease should consult a clinician.
What's the difference between L-lysine and lysine HCl?⌄
L-lysine is the biologically active form; HCl is just the salt that stabilizes it. L-lysine monohydrate is another form. All are absorbed similarly. The 'L' refers to the chiral form found in nature.
References by claim
Track Lysine with Pilora
Set up dose reminders, check interactions, and join the community in the Pilora iPhone app.
Coming to App StoreDisclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.