Orotic acid

Orotic acid, also known as pyrimidinecarboxylic acid or vitamin B13. Historically it was believed to be a vitamin but this is now known not to be the case. It is manufactured in the body by intestinal flora. It is sometimes used as a mineral carrier in some dietary supplements (to increase their bioavailability), most commonly for lithium.

Pathology
A buildup can lead to orotic aciduria.

In ornithine transcarbamoylase deficiency excess carbamoyl phospate is converted into orotic acid. Leading to typical finding of increased urine orotic acid excretion in this disorder of the urea cycle.