Indirect bilirubin of 18.1 μmol/L is a more serious condition. Bilirubin in the human body can be divided into two types: direct bilirubin and indirect bilirubin. Indirect bilirubin is also known as unconjugated bilirubin, or bilirubin that is not bound to glucuronic acid. After the destruction of red blood cells, a large amount of hemoglobin is converted into indirect bilirubin, the amount of which exceeds the processing capacity of the liver, which cannot convert all of it into direct bilirubin, resulting in an increase of indirect bilirubin in the blood. Its concentration reflects the conversion function of hepatocytes and the decomposition state of red blood cells, but clinically it also needs to be determined based on the patient’s symptoms, other indicators of liver function, and imaging of the hepatobiliary system. The reference value of indirect bilirubin is 3.4 μmol/L-17.0 μmol/L; its high value is mostly seen in the following diseases: 1. liver diseases: including acute hepatitis, hepatic necrosis, chronic hepatitis, cirrhosis, etc.; 2. hemolytic anemia; 3. blood transfusion for blood group incompatibility; 4. hepatocellular jaundice; 5. others: severe scalding, sepsis, hypersplenism, pernicious anemia pearl protein production disorder anemia, lead poisoning, physiological jaundice in newborns, and drug-related jaundice may also lead to elevated indirect bilirubin.