L-arginine is an amino acid that is 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, which 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. Some of the uses and effectiveness of L-arginine supported by scientific research include:

• Chest pain (angina): Taking L-arginine by mouth seems to decrease symptoms and improve exercise tolerance and quality of life in people with angina.
• Erectile dysfunction (ED): Taking 2.5-5 grams of L-arginine by mouth daily seems to improve sexual function in people with ED. Taking L-arginine with medications such as sildenafil and tadalafil might work better than taking either L-arginine or the medication alone.
• High blood pressure: Taking L-arginine by mouth can reduce blood pressure in healthy people, people with high blood pressure, and people with slightly high blood pressure with or without diabetes.
• A serious intestinal disease in premature infants (necrotizing enterocolitis or NEC): Adding L-arginine to formula can help treat this condition.

L-arginine is also used for many other conditions, but there is no good scientific evidence to support these other uses. L-arginine supplements are taken by many populations, including athletes and those who have certain medical conditions like high blood pressure, for a variety of reasons. They’re also used in the clinical setting to treat critically ill people or those with wounds. However, results are mixed, and L-arginine may not be as effective for some conditions as many supplement companies claim. It is important to talk to a healthcare provider before starting any new supplements like L-arginine.