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 Role of L carnitine in female infertility Reproductive Biology and Endocrinology Springer Nature Link L Carnitine: Benefits, Side Effects, FAQ, Sources, and Dosage L Carnitine Linus Pauling Institute Oregon State University