Notes: Isobutyryl-L-carnitine-d3 is intended for use as an internal standard for the quantification of isobutyryl-L-carnitine by GC- or LC-MS. Isobutyryl-L-carnitine is a natural 4-carbon acylcarnitine that is involved in fatty acid oxidation and organic acid metabolism.{32029} Elevated levels of isobutyryl-L-carnitine are associated with isobutyryl-CoA dehydrogenase deficiency.{32027,32028}