Bilirubin is formed by the breakdown of hemoglobin in the spleen, liver, and bone marrow. It can be conjugated with glucuronic acid or unconjugated (albumin bound). An increase in bilirubin concentration in the serum or tissue is called jaundice and can occur in toxic or infectious diseases of the liver. High levels of conjugated or direct bilirubin indicate that bile is not being properly excreted; therefore an obstruction may be present in the bile duct or gall bladder. High levels of unconjugated bilirubin indicate that too much hemoglobin is being destroyed or that the liver is not actively treating the hemoglobin it is receiving.