Are there any side effects of l-lysine?

High doses, maybe. Deficiency symptoms might include stomach cramps, diarrhea, hair loss weight loss, poor concentration, reproductive problems, kidney stones. It can interact with a number of antibiotics to lethal effect. It could cause severe allergic reactions, (swelling of lips and tongue, or throat closure, difficulty breathing) old people need it more than young. Athletes use it.

Related Questions

Is it reasonable to take L-lysine capsules daily (about 1500mg) to prevent latent herpese viruses? Any side-effects should I be aware of?

Yes, but it's not. necessarily effective. l-lysine may decrease the number & duration of HSV I (cold) sore outbreaks, but not necessarily HSV II (genital herpes). l-lysine can increase the amount of calcium your body absorbs. While food (like dairy) isn't a problem, a healthy young guy like you shouldn't take calcium supplements at the same time. This includes calcium-containing antacids. Read more...