Routine blood tests are one of the easiest and most direct tests that can reveal a lot of information to us. By reading a routine blood test, we can basically determine whether the subject has a blood disorder, what kind of blood disorder it might be, and what kind of further tests are needed. There are many items in a routine blood test sheet, and after some items there may be rising or falling arrows, and many people will be confused or even fearful about these items. Although an important manifestation of leukemia is a change in blood count, there are many other causes of abnormal blood tests: such as strenuous activity, colds, pregnancy and the effects of some medications. It is therefore necessary to learn to read your blood work briefly. Routine blood tests usually include white blood cells, red blood cells, hemoglobin, red blood cell pressure, average red blood cell volume, average hemoglobin content, average hemoglobin concentration, and platelet count. Among them, the most important are the three items of white blood cells, hemoglobin, and platelet count. Leukocytes: The normal value for adults is (4-10) × 109/L and for newborns is high at (15-20) × 109/L. Leukocytes include five types of cells: neutrophils, eosinophils, basophils, lymphocytes and monocytes. An increase or decrease in any of these cells may affect the total white blood cell count. The white blood cell count may be elevated when acute infections, especially septic cocci, severe tissue injury, hemorrhage, parasitic diseases (e.g., schistosomiasis, ascariasis, hookworm disease, etc.), allergic diseases (e.g., bronchial asthma, drug allergy, etc.), and acute poisoning are present. When viral infections, autoimmune diseases (such as systemic lupus erythematosus, etc.), typhoid fever, and damage by physicochemical factors (such as radionuclides, radiation, benzene, lead, mercury, etc.) may cause leukopenia. Hemoglobin: When the hemoglobin is less than 110g/L in adult females and less than 120g/L in males on multiple tests it can be called hemoglobinopenia. However, in infants and children, the hemoglobin is 20-30% higher than normal, while in some elderly and pregnant women, the decrease is called “physiological decrease”. If we exclude this cause, it is called “pathological hemoglobin reduction”, which is what we call anemia. There are many causes of anemia, and leukemia is one of them. When anemia occurs, there is no need to be nervous, as it may be related to nutrition, medication, acute and chronic blood loss, and other factors. Go to the hospital carefully to find out clearly what causes anemia. Platelets: The normal value is (100-300) × 109/L. When the number of platelets is less than 100 × 109/L, it is called thrombocytopenia. This condition can be caused by: impaired production, destruction or excessive consumption of platelets in the body. Increased platelets (>500×109/L) are seen in myeloproliferative disorders. When platelets are below 20×109/L, internal and cerebral bleeding is likely to occur, which is dangerous and needs to be treated with platelet transfusion. When we have frequent nosebleeds or wound bleeding that cannot be easily stopped in our life, we suggest you to check your blood count to see if there is thrombocytopenia. When your blood picture is within the normal range, then basically leukemia can be ruled out. If your white blood cells are high or low, don’t be nervous, but please undergo other tests (such as white blood cell classification, bone marrow aspiration) under the guidance of your doctor to clarify what exactly is causing your blood abnormalities. In short, when you see an abnormal blood count, you should not disregard it, nor should you be overly nervous.