L-Carnitine is a popular non-stimulant amino acid that is included in many fat burner, pre-workout and thermogenic products. L-carnitine is an amino acid that is produced in small amounts in the body. You can get L-carnitine from good protein sources like beef, chicken, fish and. You can also get L-Carnitine supplements in capsules, pills and liquid. L-Carnitine transports fat cells throughout the body to be used for energy. That extra energy gives you the ability to train for longer periods of time and to have more productive workouts. L-Carnitine also helps to improve circulation, which helps to get blood flowing through your body at a faster rate. Because L-Carnitine plays a major role in energy production, a lot of athletes take it to help improve endurance and to enhance their athletic performance.