What is Acetyl L Carnitine? The Role of L Carnitine in Kidney Disease and Related Metabolic Dysfunctions 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 Your dog's heart works hard and L Carnitine helps fuel every beat. This natural protein like substance supports healthy heart function by helping carry fatty acids to where the body needs them most.