The function of leukocytes is mainly to be the body’s defender, and after a cold the bone marrow produces a large number of leukocytes to fight bacteria and kill them. In addition, the total number of white blood cells increases in leukemia patients, and the total number can reach tens of thousands or hundreds of thousands, and chronic granulocytic leukemia can reach hundreds of thousands or millions. There is also exercise. After exercise, the white blood cells in the bone marrow are released into the blood, which is going to cause an increase in white blood cells. So when you check your blood, you usually need to rest for 10-20 minutes. In addition, there is also heat stroke, etc., which can also cause an increase in white blood cells. There are physiological reasons for the decrease in white blood cells. If you eat food with more pesticides and fertilizers, the white blood cells will be relatively low.