Deoxyuridine, also known as dU, belongs to the class of organic compounds known as pyrimidine 2'-deoxyribonucleosides. Pyrimidine 2'-deoxyribonucleosides are compounds consisting of a pyrimidine linked to a ribose which lacks a hydroxyl group at position 2. It is similar in chemical structure to uridine, but without the 2'-hydroxyl group. Deoxyuridine exists in all living organisms, ranging from bacteria to humans. Within humans, deoxyuridine participates in a number of enzymatic reactions. In particular, deoxyuridine can be biosynthesized from deoxycytidine through its interaction with the enzyme cytidine deaminase. In addition, deoxyuridine can be converted into uracil and deoxyribose 1-phosphate through its interaction with the enzyme thymidine phosphorylase. Deoxyuridine is considered to be an antimetabolite that is converted into deoxyuridine triphosphate during DNA synthesis. Laboratory suppression of deoxyuridine is used to diagnose megaloblastic anemia due to vitamin B12 and folate deficiencies. In humans, deoxyuridine is involved in the metabolic disorder called UMP synthase deficiency (orotic aciduria). Outside of the human body, deoxyuridine has been detected, but not quantified in, several different foods, such as lichee, highbush blueberries, agaves, macadamia nut (M. tetraphylla), and red bell peppers. This could make deoxyuridine a potential biomarker for the consumption of these foods.