4-Hydroxybutyryl-L-carnitine-13C3is carbon-13 labeled 4-Hydroxybutyryl-L-carnitine (H824652) is anarylcarnitine, which is an important metabolite used as a diagnostic tool for detecting inherited metabolic disorders. Antibodies can be raised againstL-carnitine and other carnitine-related compounds to measure the quantity of L-carnitine in biological samples and serum.