Lysine 500 mg by Thorne

If you Google lysine for cold sores, you’re in the right aisle. This essential amino acid fits adults with frequent herpes simplex outbreaks, plant-based eaters relying on grains and legumes where lysine is the limiting amino acid, and anyone with low total protein intake. Athletes during heavy training and older adults who struggle to hit protein targets also use lysine for tissue repair and recovery. If your diet already includes ample dairy, eggs, fish, or meat, you may not notice much from a low dose.

Lysine competes with arginine (another amino acid many viruses depend on) for transport into cells. Raising the lysine-to-arginine ratio is the rationale behind its use in cold sore prevention. Beyond that, lysine is required to build collagen, the structural protein in skin and tendons, and it is a precursor for carnitine, which helps mitochondria burn fat for energy. It also increases calcium absorption from the gut, a small but relevant effect if you take calcium.

Take one 500 mg capsule two to three times daily, with or without food. For recurrent cold sores, clinicians often use 1,000–3,000 mg per day for prevention, and short bursts at the higher end at the first tingle, then step back to maintenance once stable. Pairing lysine with lower-arginine eating during flares is common practice. Expect any effect on outbreak frequency within 4 to 12 weeks.

If you supplement arginine or use arginine-heavy pre-workouts, taking them alongside lysine works against your goal; separate them or reconsider. Use caution if you have kidney or liver disease, very high calcium levels, or a history of recurrent kidney stones. Pregnancy and breastfeeding are likely fine at dietary levels, but higher-dose supplementation should be cleared with your clinician. Mild nausea or stomach upset is the most common side effect.