Dihydrouracil Unit Converter

Dihydrouracil (also called 5,6-dihydrouracil or UH2) is a molecule produced when the body breaks down uracil, one of the building blocks of RNA. It is an intermediate in the three-step pyrimidine degradation pathway and is normally converted further into beta-alanine.

Measuring dihydrouracil in blood helps evaluate whether the enzymes responsible for pyrimidine breakdown are working correctly. It is typically ordered as part of a broader purines and pyrimidines panel to screen for inborn errors of pyrimidine metabolism.

When interpreted alongside uracil, the dihydrouracil-to-uracil ratio can also serve as a measure of dihydropyrimidine dehydrogenase (DPD) enzyme activity, which is important for safe dosing of fluoropyrimidine chemotherapy drugs such as 5-fluorouracil and capecitabine.

Dihydrouracil is produced throughout the body when the enzyme dihydropyrimidine dehydrogenase (DPD) reduces uracil. The liver is the primary site of pyrimidine degradation, though DPD is also active in other tissues including blood cells.