The normal value of leukocytes is (4.0~10.0)×10⁹/L. Leukocytes below 3.0×10⁹/ belong to leukopenia. Leukocytes are immune cells, and leukopenia will lead to a decrease in the body’s immune function and susceptibility to infections of various organs. In addition, the primary causes of leukopenia need to be emphasized. 1. Infection: leukopenia may be caused by ionizing radiation, cytotoxic drugs, leukemia, myeloma and other diseases, the body, in addition to the symptoms of the original disease and fatigue, weakness, dizziness and other non-specific symptoms, the risk of infection increases significantly. Common sites of infection are the respiratory, digestive and genitourinary tracts. The lower the white blood cells, the more serious the infection tends to be, with high fever and even infectious shock. 2. The manifestation of the original disease: such as acute leukemia caused by leukopenia, is very serious, may be due to the combination of anemia, bleeding, etc. in a short period of time life-threatening. Therefore, when the white blood cells are lower than 3.0×10⁹/, it is necessary to go to the hospital in time to find out the cause of the disease, and carry out treatment for the primary disease under the guidance of the physician. At the same time, pay attention to the prevention of infection, reduce access to public places and maintain hygiene.