Carnitine (L-3-hydroxy-4-N,N,N-trimethylaminobutyrate) is an essential metabolite, which has a number of indispensable roles in intermediary metabolism. First, carnitine has an important role in the transport of activated long-chain fatty acids from the cytosol to the mitochondrial matrix, where β-oxidation takes place. Secondly, carnitine is involved in the transfer of the products of peroxisomal β-oxidation, including acetyl-CoA, to the mitochondria for oxidation to CO2 and H2O in the Krebs cycle. Other functions of carnitine include modulation of the acyl-CoA/CoA ratio, storage of energy as acetylcarnitine and the modulation of toxic effects of poorly metabolized acyl groups by excreting them as carnitine esters.