The normal range of leukocytes should be (4.0-10.0)×10^9/L. There are many factors that cause high leukocytes, the common one being bacterial infections. Leukocytes mainly play a defensive role. When there is a foreign bacterial infection, the leukocytes in the bone marrow are released into the blood and participate in the process of engulfing the bacteria and killing them, resulting in elevated leukocytes in the blood. Common bacterial infections that cause elevated white blood cells include pneumonia, otitis media, tonsillitis, and cholecystitis. The body’s defense mechanisms are more complex when viral infections are present, but most viral infections, usually, do not cause changes in white blood cells, but instead may also show a mild decrease in white blood cells. Less commonly, elevated leukocytes are seen in diseases such as epidemic B encephalitis, infectious mononucleosis, and measles. Disease factors for elevated leukocytes may be caused by severe tissue injury, acute poisoning, hematologic disorders (e.g., leukemia), immune system disorders (e.g., systemic lupus erythematosus), and malignancies (especially gastrointestinal tumors), in addition to bacterial and viral infections. In addition, leukocytes may also rise in cases of over-eating, emotional stress, high or low temperatures, and in women during menstruation and pregnancy and childbirth, but they are usually transient and can be relieved by moderate rest, etc.