L-Lysine is an essential amino acid necessary for growth, development, tissue maintenance and repair. Jarrow Formulas’ L-Lysine 500 is the HCl (hydrochloride) form of L-Lysine which is twice as stable as the monochloride form. 625mg of L-Lysine HCl yields 500 mg of elemental L-Lysine.

Lysine is an amino acid not produced by the body, but essential to the growth of protein molecules in the body. It is necessary for tissue repair and growth, and for producing antibodies, enzymes, and hormones. Lysine is found in other protein sources, such as red meats, chicken, and turkey. Most individuals have an adequate intake of lysine; however lysine levels may be low in vegetarians and low-fat dieters. Without enough lysine or any other of the eight essential amino acids, the body cannot build protein to sustain muscle tissue.

The body only uses L-Lysine to build protein. Since amino acid molecules are asymmetrical, each amino acid exists as both a right- and left-handed form, distinguished as "D" and "L" respectively. As a supplement, L-lysine is used to treat the herpes simplex virus, help prevent osteoporosis and cataracts, and boost the immune system.

Lysine appears to help the body absorb and conserve calcium. Lysine has many functions in the body because it is incorporated into many proteins, which are used by the body for a variety of purposes. Lysine interferes with replication of herpes viruses and is therefore often prescribed by doctors to people with cold sores or genital herpes.