Glutamyl transpeptidase in normal human serum is mainly derived from the liver. Glutamyl transpeptidase is distributed in human tissues, most in kidney, followed by pancreas and liver, and most in liver in embryonic stage, in which it is mainly distributed in hepatocyte plasma and intrahepatic bile duct epithelial cells. The normal value of glutamyl transpeptidase is 3-50 U/L. If it rises to 90 U/L, it is mildly elevated. The causes of elevated glutamyl transpeptidase are divided into physiological and pathological. Physiological is mainly caused by severe fatigue and frequent staying up late, while pathological can occur in acute hepatitis, chronic active hepatitis and cirrhosis of the liver in the decompensated stage with moderate elevation. In case of obstructive jaundice, glutamyl transpeptidase can be significantly elevated in blood due to the backflow of glutamyl transpeptidase into blood due to the obstruction of excretion, and glutamyl transpeptidase can be hyper-synthesized in liver in primary liver cancer; in addition, glutamyl transpeptidase can also be significantly elevated in alcoholic liver, fatty liver, drug-related liver damage, alcoholic patients, primary biliary cholangitis, primary sclerosing cholangitis, etc. Therefore, glutamyl transpeptidase 90U/L is only mildly elevated, which is not necessarily liver cancer. It is recommended to go to hospital for relevant examination to confirm the cause of abnormal liver function and carry out symptomatic treatment.