Serum alanine aminotransferase (aminotransferase for short) is found in the mitochondria of liver cells and is released from liver cells into the blood whenever the liver is damaged by inflammation, necrosis, or toxicity. Therefore, diseases of the liver itself, especially viral hepatitis, hepatic sclerosis, liver abscess, liver tuberculosis, liver cancer, fatty liver, and hepatic sinusoidal degeneration, can cause various degrees of transaminase elevation. In addition to the liver, other organ tissues in the body such as heart, kidney, lung, brain, testes and muscle also contain this enzyme. Therefore, increased aminotransferases in the blood can be seen in myocarditis, pyelonephritis, lobar pneumonia, tuberculosis, encephalitis B, polymyositis, acute septicemia, enteric typhoid fever, rheumatoid fever, malaria, cholecystitis, leptospirosis, influenza, measles, schistosomiasis, and crush syndrome. Because transaminases are excreted from the bile ducts, they can also be elevated if there are bile duct, gallbladder and pancreatic disorders and bile duct obstruction. Common clinical conditions include cholecystitis, bile duct roundworms, hepatobiliary duct stones, gallbladder and bile duct tumors, peribiliary carcinoma, congenital bile duct dilatation, acute and chronic pancreatitis, pancreatic head cancer and hemorrhagic necrotizing pancreatitis. Pharmacogenic or toxic liver damage, as well as drug allergy can cause elevated transaminases, often accompanied by bilious jaundice and hepatocellular damage. There are clinical reports of elevated transaminases within 12 to 48 hours of drug administration, with a peak in 4 to 10 days, and normalization within 3 weeks if the drug is discontinued promptly. Other medical diseases such as systemic lupus erythematosus, hyperthyroidism, diabetes mellitus, malignant reticulocytosis, heart failure, rheumatic fever, peptic ulcer, acute and chronic gastroenteritis, and uremia can cause elevated aminotransferases. Normal pregnancy, gestational toxicity, and acute fatty liver in pregnancy are also common causes of elevated aminotransferases. In addition, transaminases can also be increased after strenuous exercise. Lactate metabolism causes relative hypoxia and hypoglycemia in the body, resulting in increased hepatocyte membrane permeability and elevated transaminases. It can be seen that the causes of elevated serum aminotransferases are multifaceted. When encountering people with elevated single aminotransferases clinically and in life, one should never arbitrarily affirm that it is hepatitis. A detailed history must be taken, necessary physical and chemical examinations must be performed, and the specific diagnosis of hepatitis A, B, C, D, E and G and liver biopsy can be combined to help confirm the diagnosis.