Usually, the radiation dose from a CT examination does not directly cause a drop in white blood cells. If a drop in white blood cells is found, it may be caused by other reasons, and whether it can be recovered after targeted treatment is related to the disease condition. The main causes of white blood cell drop are viral infections, aplastic anemia, hypersplenism, and drug factors. 1. Viral infections, such as influenza, chicken pox, etc., the blood picture shows a decrease in white blood cells and an increase in lymphocytes, in addition to fever, rash and other symptoms. Generally, after symptomatic treatment and infection control, the white blood cells can recover by themselves. 2. Aplastic anemia: generally manifested as a decrease in white blood cells, red blood cells, platelets, etc., with easy anemia, easy to bleed, easy to be infected, etc., and can be diagnosed by bone puncture. Immunosuppressive therapy, blood transfusion therapy, bone marrow transplantation therapy and other methods are often used, and the white blood cells may recover to different degrees after treatment. 3. Hypersplenism: It is mainly manifested by splenomegaly and decrease of blood cells, which can be diagnosed by bone marrow image, blood image and imaging examination, and the blood cell level can be gradually increased after removing the primary disease or splenic embolization/removal. 4. Drug factors: Most drugs can cause leukocyte decline, such as sulfonamides, chemotherapy, antibiotics, antipyretic drugs, and anti-tuberculosis, hyperthyroidism and other drugs. Generally follow the doctor’s instructions to adjust the dose of drugs or stop changing drugs, white blood cell levels can be gradually restored. Warm reminder: During the treatment period, we should regularly review the blood routine, follow the doctor’s instructions to standardize the treatment, and if there is any discomfort, consult the doctor in time.