Orotic acid is a pyrimidinedione and a carboxylic acid. Historically it was believed to be part of the vitamin B complex and was called vitamin B₁₃, but it is now known that it is not a vitamin. The compound is manufactured in the body via a mitochondrial enzyme, dihydroorotate dehydrogenase or a cytoplasmic enzyme of pyrimidine synthesis pathway. It is sometimes used as a mineral carrier in some dietary supplements (to increase their bioavailability), most commonly for lithium orotate.