L-carnitine is a chemical that is made in the human brain, liver, and kidneys. It helps the body turn fat into energy.

L-carnitine is important for heart and brain function, muscle movement, and many other body processes. The body can convert L-carnitine to other chemicals called acetyl-L-carnitine and propionyl-L-carnitine. But it’s not clear whether the benefits of these other carnitines are the same.