The causes of low total bilirubin are physiologic and pathologic. Physiological causes include micronutrient deficiencies, vitamin deficiencies, etc. Pathological causes include anemia, chronic kidney disease, peptic ulcers and other diseases. Bilirubin is produced by the metabolism of hemoglobin in the body after the aging and apoptosis of red blood cells. 1. Physiological causes: such as irrational dietary structure, resulting in the lack of folic acid, vitamin B1, iron and other deficiencies, reduced erythropoiesis. 2. Pathological causes: Clinical diseases that can lead to low total bilirubin mainly affect the production of red blood cells. Such as iron deficiency anemia, aplastic anemia can lead to erythropoietic disorders; such as chronic kidney disease can lead to erythropoietin reduction, erythropoietic disorders; such as peptic ulcer bleeding can lead to a reduction in erythrocytes. Low total bilirubin can also be seen in the test error, such as drinking water before the test, resulting in dilution of blood. If there is no significant abnormality in other liver function indexes, it is recommended that the test be repeated at a later date, according to the doctor’s instructions.