Bilirubin is a type of bile pigment, the main pigment in human bile, which can be divided into total bilirubin, direct bilirubin and indirect bilirubin. Bilirubin is a very important basis for determining jaundice and is also a very important indicator of liver function. Increased bilirubin can be seen in hemolytic diseases, hepatocellular diseases, and obstructive jaundice. If direct bilirubin is predominantly elevated, it may indicate obstructive jaundice, which can be caused by stones in the biliary system, tumors, and so on. If indirect bilirubin is predominantly elevated, it may indicate hemolytic jaundice, which is mainly caused by blood group incompatibility during blood transfusion. If all three bilirubins are elevated, it may indicate hepatocellular jaundice, which can be seen in patients with severe hepatitis, cirrhosis and liver cancer.