L Carnitine 3000 San Nutrition What Is L Carnitine? L Carnitine Benefits, Dosage & When To take? MYPROTEIN The Marathon L Carnitine helps the body turn fat into energy. If your plan is to use this supplement to optimize energy during your workout, it's best to take it prior to Most people use L Carnitine wrong. They take it alongside a high carb diet expecting it to burn fat. Biologically, thats almost impossible., L Carnitine is an amino acid derivative that transports