Hepatitis B ALT, also known as alanine aminotransferase, has a normal value of 10-40 U/L. It is found mainly in the liver, in the body’s liver cells, so its serum level is low when normal. When the liver cells are damaged, the membrane permeability of the liver cells increases and the intracellular alanine aminotransferase can be released into the blood, resulting in an increase in the serum level of alanine aminotransferase. In acute viral hepatitis B, alanine aminotransferase is significantly increased and can reach up to 100 times the upper limit of normal; in chronic viral hepatitis, alanine aminotransferase can be mildly increased.