Anyone who gets cold sores NEEDS to be on a higher dose than the standard 500mg/day; the quality of this supplement is unmatched and yet it's super affordable. I researched dosages and apparently 2000-4000mg is necessary during an outbreak, and when I felt one coming on I took that amount and it prevented it. Valtrex is super destructive to the gut so Lysine supplementation is keyyyy to preventing outbreaks long term. I know it works because I get regular outbreaks when I don't take lysine, and lysine prevents me from getting outbreaks at all (you just need to up the dose when you feel one coming on).