White blood cells of 2.5 x 10⁹/L are relatively low and may lead to a decrease in autoimmunity, which tends to increase the risk of infections in various systems throughout the body. The normal range of white blood cells in adults is (4~10) x 10⁹/L, and elevated or lowered suggests that a disease may be present. If the white blood cell count of the human body is lower than normal, it means that the number of white blood cells in the body is low, which may be related to the following diseases: ① hematological diseases: aplastic anemia, megaloblastic anemia, leukemia, myelodysplastic syndromes, etc.; ② autoimmune diseases, such as systemic lupus erythematosus, rheumatism, etc.; ③ viral infections; and ④ simple hyper-splenism. When the white blood cell count is low, it is necessary to consult a doctor in time to clarify the cause of the disease and then carry out targeted treatment under the guidance of the physician.