GNC L-Carnitine 500mg Dietary Supplement Support even the most punishing workout regimen with GNC L-Carnitine 500mg Dietary Supplement. A nutritional compound derived from amino acids, carnitine facilitates the metabolism of long-chain fatty acids.* Ideal as a pre- or post-workout supplement, it also fuels exercise and supports recovery.* Helps Facilitate Fatty Acid Metabolism Found abundantly in red meat, carnitine is stored in skeletal muscles where it is needed to transform fatty acids into energy. This non-essential amino acid can be synthesized by the body and facilitates the metabolism and transport of long-chain fatty acids.*