A bilirubin test measures the levels of bilirubin in the blood, which is produced during the breakdown of red blood cells and processed by the liver. Higher bilirubin levels can indicate liver or bile duct problems or increased red blood cell destruction. Bilirubin testing is usually done as part of a group of liver function tests to investigate jaundice, determine possible bile duct blockages, detect or monitor liver disease, evaluate anemia, and follow treatment effectiveness or potential drug toxicity. Common related tests include liver function tests, albumin and total protein levels, complete blood counts, and prothrombin time.