L-arginine is an amino acid that has numerous functions in the body. It helps the body get rid of ammonia (a waste product), is used to make compounds in the body such creatine, L-glutamate, and L-proline, and can be converted to glucose and glycogen if needed.

L-arginine is used to make the nitric oxide, a compound in the body that relaxes blood vessels. Preliminary studies have found that L-arginine may help with conditions that improve when blood vessels are relaxed (called vasodilation), such as atherosclerosis, erectile dysfunction, and intermittent claudication.

L-arginine is also involved in protein formation. In larger amounts, L-arginine stimulates the release of hormones growth hormone and prolactin.