The reference range for total bilirubin is 3.4 to 17.1 umol/L in adults. Bilirubin is a product of phagocytosis, breakdown and destruction of senescent erythrocytes in the blood by mononuclear macrophages in the liver, spleen and bone marrow. After the disintegration of erythrocytes, the proper hemoglobin is formed into unconjugated bilirubin by the action of enzymes, which is then processed by the liver to produce conjugated bilirubin. When the bilirubin in the blood is too high, it causes jaundice, so the ratio of conjugated bilirubin to total bilirubin is commonly used to determine the type of jaundice in clinical practice. Measurement of total bilirubin can assist in the early diagnosis of certain hepatobiliary diseases, such as hepatitis without jaundice, decompensated cirrhosis, and hepatocellular carcinoma. However, total bilirubin changes alone are not sufficient to confirm the diagnosis, and other laboratory tests are needed to reach a conclusion.