In general, the normal reference range of alanine aminotransferase is 0-40U/L (the specific reference range is subject to the local hospital). 250U/L of alanine aminotransferase may be caused by physiological factors such as overexertion, strenuous exercise, etc., which can be recovered on its own, and is generally not dangerous; or it may be associated with acute and chronic hepatitis, cirrhosis and liver cancer, which is a more dangerous situation. Alanine aminotransferase is a kind of enzyme involved in protein metabolism in human body, which accelerates the transformation of protein and amino acid in the body, and it is widely found in various tissues of human body, such as muscle and bone, and it is the most abundant in the cytoplasm of liver cells. When liver cells are damaged, alanine aminotransferase in the cytoplasm will be released into the blood, causing elevation of serum alanine aminotransferase. Elevated alanine aminotransferase is indicative of hepatocyte damage and may be associated with acute and chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Alcohol, chemicals such as carbon tetrachloride, and heavy metals such as mercury can also cause elevated alanine aminotransferase. Some non-hepatophilic viral infections such as colds and fever, drug liver injury, and hepatic stasis caused by cardiac insufficiency can cause elevation of alanine aminotransferase. Physiologic elevations can be observed with rest, while pathologic elevations require hepatoprotective therapy and etiologic treatment.