There are more than 20 indicators in blood routine, which can be divided into three parts, white blood cells, red blood cells and platelets, as follows: 1. In the white blood cell part, we mainly look at the total number of white blood cells and white blood cell classification, generally the total number of white blood cells is increased, and the neutrophils in the classification are also high, it will be considered a bacterial infection. If the total white blood cell count is normal or slightly high, but the proportion of lymphocytes is increased and the proportion of neutrophils is decreased, this is considered a viral infection. If eosinophilia is increased in the leukocyte classification, it is considered that there are allergic diseases, such as allergy and allergic asthma can cause eosinophilia, and parasites can also cause eosinophilia. 2. In the red blood cell part, we mainly look at the red blood cell count and hemoglobin content, if both indicators are low, it can be determined that it is anemia, and then combined with the rest of the red blood cell indicators, we can initially determine the anemia 3. Platelets mainly play an anticoagulant role, and thrombocytopenia will hinder the coagulation function of human body, and thrombocytopenia can be seen in thrombocytopenic purpura, aplastic anemia, or some leukemia and tumor can cause thrombocytopenia.