L-arginine is an amino acid naturally found in red meat, poultry, fish, and dairy. It is necessary for making proteins and is commonly used for circulation.

L-arginine is converted in the body into a chemical called nitric oxide. Nitric oxide causes blood vessels to open wider for improved blood flow. L-arginine also stimulates the release of growth hormone, insulin, and other substances in the body. It can be made in a lab and used in supplements.

People use L-arginine for chest pain and various blow flow issues, erectile dysfunction, high blood pressure during pregnancy, and a serious disease in premature infants called necrotizing enterocolitis (NEC). It's also used for many other conditions.