Leukemia can present with a decrease in white blood cells, but it cannot be judged as leukemia based on the amount of white blood cell decrease. This is because routine blood results are not a diagnostic criterion for leukemia. Low white blood cells are not necessarily leukemia, and leukemia is not judged solely on the basis of the degree of white blood cell reduction. 1. Lowering of white blood cells: common in infections, physical and chemical injuries, autoimmune diseases, blood diseases (aplastic anemia) and hypersplenism. 2. Changes in white blood cells in leukemia patients: (1) Acute leukemia: most patients with acute leukemia have increased leukocytes, even up to 100×10^9/L. Some patients have normal or decreased leukocytes. (2) Acute granulocytic-monocytic leukemia: leukocytes often appear to be increased, and some patients may be normal or decreased. (3) Acute megakaryocytic leukemia: some patients have low white blood cells and some have elevated white blood cells. Therefore, you can not judge whether it is leukemia solely based on the degree of reduction of white blood cells. It should be analyzed and judged by other relevant examinations, such as bone marrow examination. If the above test results occur, it is recommended to go to the hospital in time, and under the guidance of the physician to carry out regular treatment as soon as possible.