Routine blood tests can find out if a person is anemic and also make a general judgment about the cause of anemia. First, the number of red blood cells, if the number of red blood cells is significantly lower than normal, then there is anemia. Second, red blood cell pressure, if the red blood cell pressure is reduced, it means that the red blood cell volume is insufficient, and there is also anemia. Third, hemoglobin concentration, which is also an indicator of the degree of anemia. If the hemoglobin concentration decreases, there is anemia, and the more serious the decrease in hemoglobin concentration, the more serious the degree of anemia. In addition to these three indicators, the average volume of red blood cells, the average hemoglobin volume and the average hemoglobin concentration of red blood cells should be observed, which are very helpful in determining the type of anemia. If there is a significant increase in all three indicators, then it is a macrocytic anemia and the first thing to consider is megaloblastic anemia.