There are many liver function tests, which often confuse patients and make them wonder what these laboratory tests actually mean. In terms of the nature of the tests, these common clinical indicators are mainly divided into three categories. First, the indicators reflecting liver parenchymal damage: alanine aminotransferase (ALT) and aspartate aminotransferase (AST). These two enzymes are mainly found in the cytoplasm of liver cells. They can be detected in normal people, but they do not exceed 40u/ml (nowadays they are detected by the Wright’s method), and exceeding the upper limit of normal indicates liver cell damage. There are both physiological and pathological causes for the elevation of these two enzymes. The physiological causes are mainly pregnancy, staying up late, fatigue, alcohol consumption, strenuous exercise, cold and emotional factors. Pathological causes are mainly acute and chronic hepatitis, acute pancreatitis, acute cholecystitis, biliary obstruction, cholelithiasis, acute myocardial infarction, pulmonary infarction and multiple organ failure caused by various reasons (viruses, drugs, alcohol and autoimmunity). If you find that your transaminases are abnormal, you must see a doctor who will do targeted tests such as viral hepatitis index, autoantibodies and abdominal ultrasound to clarify the cause of the abnormal transaminases based on your medical history and physical examination. Physiological elevations usually do not require treatment and will recover on their own after eliminating the trigger. Pathological ones need to be distinguished as acute or chronic, as the interval between treatment medication and regular review may be different. Secondly, indicators reflecting bilirubin metabolism and cholestasis. These indicators include total bilirubin (Tbil), direct bilirubin (D-bil), indirect bilirubin (I-bil) serum bile acids (TBA) and alkaline phosphatase (ALP). Bilirubin is also commonly known as jaundice in the general population. There are four general causes of jaundice. The first is jaundice caused by liver cell damage, the second is jaundice caused by biliary obstruction, the third is hemolytic jaundice caused by red blood cell destruction, and the fourth is physiological jaundice, mainly in newborns. The jaundice caused by these conditions will have different characteristics depending on the cause.TAB is a product of cholesterol decomposition and metabolism in the liver.The concentration of TAB in the blood of normal people is very low.Its production and metabolism are very closely related to the liver.Once when the liver is damaged, the TBA in the serum will rise, and thus the TBA in the blood is also an important indicator of liver parenchymal damage. In obstructive jaundice, in addition to abnormal TBA, there will be simultaneous elevation of ALT, γ-GGT and ALP. Some pregnant women may also have abnormal bile acid metabolism resulting in elevation, and such pregnant women are prone to cholestasis. Third, indicators reflecting the synthetic function of the liver. Total protein (TP), albumin (ALB) globulin (GLO) cholinesterase (CHE), etc. Impaired liver function can cause a decrease in the above proteins, but certain diseases can cause an increase in globulins. Serum protein is one of the most abundant substances in the solid component of blood. Total serum protein mainly reflects the synthetic function of the liver and the loss of protein due to kidney disease.