Carnitine is an important naturally occurring molecule that plays a critical role in β-oxidation by transporting long-chain fatty acids into the mitochondrial matrix. Dietary sources include red meat, dairy, poultry, and fish, but it may also be produced endogenously from lysine and methionine. Several genetic conditions including inborn errors of metabolism require carnitine supplementation for treatment. Primary carnitine deficiencies may present in the first couple of years of life with symptoms including hypoketotic hypoglycemia and liver disease.