Most people talk about carnitine like it is one supplement. It is not. Acetyl L carnitine and L carnitine L tartrate do different jobs, and picking the wrong one for the wrong goal is where people L Carnitine: Benefits, Uses, Side Effects, and More If you are like a lot of people, you may have never heard of carnitine but this important nutrient is critical for our body's ability to optimally burn fat required for energy. L Carnitine