Comparison of short term and long term effects of peroral L carnitine intake: clinical implications of elevated TMAO levels in cardiovascular complications What is carnitine? Carnitine is produced in the body from the amino acid lysine and naturally occurs in some foods. It supports energy metabolism and muscle function, which are important factors in Carnitine: Genetic Variants Affecting Mitochondrial Energy and Health Acetyl L Carnitine When to take L carnitine: Dosage, forms, and side effects