Leukocytes 27 x 10^9/L are abnormal and it is impossible to generalize whether they are serious or not. If the high white blood cells are caused by infectious factors such as acute appendicitis, it is usually not serious. However, if the high white blood cell count is caused by a disease of the hematopoietic system, such as acute leukemia, the situation is more serious. The normal adult white blood cell count is (4~10) x 10^9/L. White blood cells of 27 x 10^9/L are considered high, and the severity cannot be generalized. If the white blood cells are elevated due to infectious diseases such as acute appendicitis, acute cholangitis, pneumonia, etc., the white blood cells can mostly be lowered through active anti-infectious treatment, which is generally not considered serious. However, if the leukocyte 27×10^9/L is caused by diseases of the hematopoietic system, such as acute leukemia, myeloproliferative neoplasms, etc., the situation is more serious because of the difficulty of treatment and the poorer prognosis of patients. For patients with leukocytes 27×10^9/L, further examination should be conducted to clarify the diagnosis and active treatment.