A form of carnitine, which is a substance made in muscle and liver tissue and found in certain foods, such as meat, poultry, fish, and some dairy products. L-carnitine is also a drug that is used to treat patients who do not make enough carnitine and is being studied as a way to prevent tissue damage caused by chemotherapy. Carnitine is a type of dietary supplement. Also called Carnitor and levocarnitine.