Propionyl-L-carnitine is a chemical naturally made in the body. It’s related to two other compounds called L-carnitine and acetyl-L-carnitine. Propionyl-L-carnitine helps the body produce energy. It’s important for heart function, muscle movement, and many other body processes. It also seems to help increase circulation. People use propionyl-L-carnitine for chest pain, heart disease, heart failure, athletic performance, chronic fatigue, and many other conditions