The normal value of alanine aminotransferase ranges from 5 to 40 U/L (rate method, 37℃), the reference range is different in different hospitals, different instruments, different testing methods, etc., the specific local hospital laboratory test shall prevail. Alanine aminotransferase is a group of enzymes that catalyze the amino transfer reaction between amino acids and α-keto acids, and is used for liver function tests. Its main distribution is in the liver, followed by skeletal muscle, kidney, cardiac muscle and other tissues. In hepatocytes, alanine aminotransferase is found primarily in non-mitochondria. The normal value range of alanine aminotransferase is related to the hospital, instrument and test method, etc. The reference value range of the rate method (37℃) commonly used in the clinic is 5~40U/L; and the reference value range of the endpoint method (Lysimeter method) is 5~25 Carmen units. Elevated alanine aminotransferase is mainly seen in viral hepatitis, alcoholic liver disease, cirrhosis, drug-induced liver injury, and intra- and extra-hepatic cholestasis. If abnormal alanine aminotransferase values are found, attention should be paid to timely consultation, identification of the cause of the disease, and further treatment or therapy as prescribed by the doctor.