L-Carnitine is a naturally occurring amino acid derivative. It is synthesized by our body using the amino acids lysine and methionine. We also need vitamin C for this synthesis to work properly. While our bodies produce adequate amounts of L-carnitine, you can also get extra L-carnitine from meat and fish. Vegetarians and vegetarians may be deficient in adequate amounts of the amino acid in their diets and may need to obtain L-carnitine from supplements.