Carnitine can be found in many forms, including acetyl L-carnitine, L-carnitine tartrate, L-carnitine fumarate and the most common form, free form L-carnitine. Found abundantly in skeletal and heart muscle, we need carnitine to increase energy levels. It is involved in energy metabolism and mitochondrial protection, which means your cells are more protected and your body gains more energy. Carnitine takes the fat in our bodies and uses it to produce this energy. Different forms of carnitine perform different functions.