Low blood white blood cells are often seen in four situations, one, infection, usually the human body in bacterial infections leukocytes increased, while the total number of leukocytes decreased in viral infections, because the activation of cellular immunity and lymphocyte-based, this time should be actively antiviral treatment, you can take drugs to increase leukocytes as appropriate. Second, drug factors, such as the treatment of hyperthyroidism drugs, such as methimazole, propylthiouracil, etc. can cause a drop in white blood cells. In addition, analgesics, sulfonamides, antibiotics, etc., if the leukocytes drop significantly after taking the drugs, it is necessary to stop the drugs. Third, blood system diseases, such as aplastic anemia and other bone marrow hematopoietic abnormalities, can also reduce the number of leukocytes, which are often reduced in all three lines. Immune system diseases, such as rheumatoid arthritis and systemic lupus erythematosus, can also cause a decrease in white blood cells. When the patient’s white blood cells decrease, the body’s resistance decreases and the patient is more prone to infection.