Carnitine, also known as L -carnitine or levocarnitine, is a quaternary ammonium compound biosynthesized from the amino acids lysine and methionine. It helps in the consumption and disposal of fat in the body because it is responsible for the transport of fatty acids from the cytosol into the mitochondria. It is often sold as a nutritional supplement. Carnitine was originally found as a growth factor for mealworms and labeled vitamin Bt. Natural carnitine is the L -stereoisomer.