A white blood cell count below 4.0 x 10^9/l is leukopenia requiring treatment. In addition, some physiologic decreases do not require treatment; decreases caused by blood disorders, etc., require active treatment. White blood cells are immune cells, which can effectively kill pathogens, defend against external invasive substances, and also identify and kill tumor cells. When the white blood cell count is lower than 4.0×10^9/l, it can be manifested as a decline in immune function, which can easily lead to the occurrence of infections or aggravation of infections, and the risk of infections is significantly aggravated, as well as the body’s ability to recognize and kill tumor cells. Physiological leukopenia is related to the abnormal distribution of leukocytes in the human body, generally the degree of reduction of peripheral leukocytes is very small, and there are no obvious clinical symptoms, generally do not need special treatment, dynamic observation can be. Pathological leukopenia can be seen in leukemia, myelodysplasia, aplastic anemia, viral infections, etc. After a clear diagnosis, it is necessary to actively treat the primary disease, and if necessary, it is also necessary to elevate the white blood cell therapy. When the white blood cell count is low, it is recommended to consult a doctor in time, under the guidance of a professional doctor, actively search for the cause of the disease, make a clear diagnosis, and standardize the treatment in time.