DESC: L Lysine [Structural, Circulatory, Immune] is an essential amino acid (cannot be produced by the body) required by the body for the manufacture of proteins. It helps ensure adequate absorption of calcium and the formation of collagen for bone, cartilage and connective tissue. L-lysine strengthens circulation and helps the immune system manufacture antibodies. It also has been used for cold sores. Each capsule contains 500 mg of l lysine monohydrochloride.