L-lysine is an amino acid required for normal growth and development in infants and for maintaining nitrogen balance in adults. It is classified as an essential amino acid, which means that it is required for good health but cannot be manufactured by the body, and therefore must be provided by the diet. Good sources of L-lysine include meat, fish, legumes, and dairy products. It is also available as a dietary supplement.
Most studies on L-lysine and herpes have used 900 to 1,200 mg per day. L-lysine has very low toxicity and appears to be well tolerated at this dosage range.