Peripheral blood tests are blood other than bone marrow, often checking the ends of the fingers, earlobe blood, and peripheral venous blood tests. It is usually a routine blood test, which looks at red blood cells, white blood cells, platelets and hemoglobin. The initial screening is for the presence of anemia and the possibility of hematologic disorders. Then there is the possibility of bacterial infection and viral infection. Then there are biochemical tests, such as liver function, which mainly reflects the level of transaminases and bilirubin in the liver. The kidney function mainly reflects the creatinine and urea nitrogen level of the kidney. Then there are tumor marker tests, which can screen for tumor changes at an early stage. Then there is the thyroid function test, to check hyperthyroidism and hypothyroidism. The first thing to look at is whether there are symptoms, and then the doctor will select a certain list of tests according to the symptoms.