L-carnitine is an essential molecule for cellular metabolism and plays an important role in the transfer of long-chain fatty acids across the inner mitochondrial membrane.  This process requires enzymes and transporters and defects in any of these can cause disorders of the carnitine system. Deficiency of the OCTN2 carnitine transporter causes primary carnitine deficiency. Secondary carnitine deficiencies are seen in metabolic disorders such as organic acidemias, during hemodialysis, cardiomyopathy, reproductive disorders and other disease conditions.  Early diagnosis and initiation of treatment with L-carnitine can improve outcomes and management of clinical symptoms.