L carnitine is a naturally occurring amino acid structure that is made in the human brain, liver, and kidneys. L carnitine plays a critical role in energy production, as it converts fat into energy. Acetyl L Carnitine, 500 mg, 120 Vegetarian Capsules Ortho Molecular Products L Carnitine 60 Capsules Pine Street Clinic L Carnitine 500 mg Supplement Energy and Fat Metabolism Support ALCAR Supplement for Cognitive Function and Stamina L Carnitine: Benefits, Uses, and Side Effects Lifespan Research Institute