Bilirubin is a product that results from the breakdown of hemoglobin. Total and direct bilirubin are usually measured to screen for or to monitor liver or gallbladder problems. This test is useful in determining if a patient has liver disease or a blocked bile duct.If your doctor thinks you have signs or symptoms of liver damage, liver disease, bile duct blockage, hemolytic anemia, jaundice, or liver-related metabolic problem, he will have you do this test.