Depending on the form of bilirubin present in serum, hyperbilirubinemia can be further classified as unconjugated (indirect) or conjugated (direct). Unconjugated hyperbilirubinemia (albumin-bound) usually results from increased production, impaired hepatic uptake, and decreased conjugation of bilirubin.

In contrast, conjugated bilirubin is water soluble. This allows it to travel through the bloodstream without requiring transport proteins like albumin, which means that it can also be excreted out of the body. In the next section, we will explore the metabolic pathway of bilirubin in more detail. Bilirubin Metabolism 1 – Creation of Bilirubin