Serum enzyme tests are commonly used, including alanine aminotransferase (commonly known as glutamate aminotransferase ALT), portal aminotransferase (commonly known as glutamate aminotransferase AST), alkaline phosphatase (ALP), and gamma-glutamyl transpeptidase (gamma-GT or GGT). Among the various enzyme tests, ALT and AST can sensitively reflect the presence or absence of hepatocyte damage and the degree of damage. In acute viral hepatitis, drug or alcohol-induced acute hepatocellular injury, serum ALT is the most sensitive, and ALT rises sharply before the appearance of clinical symptoms such as jaundice, while AST also rises, but the degree of AST rise is not as high as ALT. In chronic hepatitis and cirrhosis, AST rises more than ALT, so AST mainly reflects the degree of liver damage. In severe hepatitis, due to massive hepatocyte necrosis, ALT in the blood gradually decreases, while bilirubin progressively increases, i.e., the phenomenon of “bile enzyme separation”, which is often a precursor of liver necrosis. In the recovery period of acute hepatitis, if there is a normal ALT but the γ-GT continues to rise, it often indicates the chronicity of hepatitis. In chronic hepatitis, if the γ-GT continues to exceed the normal reference value, it indicates that the chronic hepatitis is in the active stage.