L-Carnitine 500mg 120 caps from Source NaturalsL Carnitine 250 mg and 500 mg Capsules L Carnitine is an amino acid found in high levels in muscle tissue. Carnitine plays an essential role in fat metabolism, by transporting long chain fatty acids into the mitochondria of the cell, where they are burned for energy in a process called beta oxidation. Beta oxidation is especially important for our muscles, which largely depend on fatty acids for energy. Supplement Facts for 500 mg Serving Size: 1