Direct Bilirubin Unit Converter

Direct bilirubin, also called conjugated bilirubin, is the water-soluble form of bilirubin that has been processed by the liver. It represents the portion of bilirubin that the liver has modified by attaching glucuronic acid, making it ready for excretion into bile.

Bilirubin is a yellow pigment produced when red blood cells break down at the end of their lifespan (approximately 120 days). The initial form, called indirect or unconjugated bilirubin, is transported to the liver bound to albumin. Once conjugated in the liver, direct bilirubin travels through bile ducts into the intestine where bacteria convert it to compounds that give stool its brown color.

Normal direct bilirubin levels in adults are typically 0 to 0.3 mg/dL. Elevated levels suggest the liver is conjugating bilirubin normally but there is difficulty excreting it, pointing to bile duct obstruction or liver disease rather than problems with red blood cell breakdown.

Direct bilirubin is produced in the liver when the enzyme UDP-glucuronosyltransferase (UGT1A1) conjugates unconjugated bilirubin with glucuronic acid. The unconjugated bilirubin originates primarily from the breakdown of hemoglobin in aging red blood cells (about 80%) and from other heme-containing proteins such as myoglobin and cytochromes (about 20%).