Bilirubin is formed as a result of hemoglobin degradation. Normally, senescent red blood cells are removed from circulation and the bilirubin that is formed is processed by the liver. The normal level of serum bilirubin for adults is 0.2-1.0 mg/dL.
Bilirubin levels increase with some liver disorders and also in anemia that is a result of a hemolytic process. Patients may display jaundice when serum bilirubin levels exceed 2.0 mg/dL.
Persons with beta thalassemia major usually have an increased bilirubin level. This bilirubin is typically the unconjugated fraction of bilirubin.