With the improvement of living standards, people’s health care awareness is getting stronger and stronger, and health checkups have become a must-do “health homework” for most people every year. Routine blood test is a routine and necessary item for health checkups because it is simple and easy to perform and can reflect the basic condition of blood to a certain extent, and white blood cell (WBC) count is an important indicator in routine blood test. When you see an increase in white blood cells in the blood routine, don’t forget to think more because the following reasons can also lead to elevated white blood cells: 1. Leukemia: In granulocytic leukemia, especially in chronic granulocytic leukemia, the total number of white blood cells is significantly higher and can be above (100 to 600) × 109/L. Acute granulocytic leukemia (M1, M2), acute promyelocytic leukemia (M3 type) granulocytes can generally increase to (10-50) × 109/L. 2, malignant tumors: some liver cancer, gastric cancer, etc., because the cancer tissue can produce pro-granulocytic factors, the breakdown products of necrosis stimulate the release of granulocytes in the bone marrow into the blood, can appear elevated white blood cells, mainly neutrophils. 3. Diabetic ketoacidosis: metabolic toxicity, such as diabetic ketosis, uremia, etc., stimulates the body to cause leukocyte reactive increase. 4, Acute poisoning: Commonly seen in chemical and biotoxin poisoning, such as sleeping pills, organophosphorus poisoning, insects, and snake toxins, can also cause reactive bone marrow hyperplasia, leading to leukocytosis. 5. Extensive tissue damage or necrosis: severe trauma, extensive burns, myocardial infarction, pulmonary infarction, etc., leukocytes are significantly elevated, with predominantly neutrophil granulocytes. In addition to these pathological causes, do not forget that there are also physiological causes: satiety, emotional excitement, strenuous exercise, high temperature or cold, female menstruation, pregnancy and childbirth, etc. can cause a transient increase in white blood cells. In addition, they can fluctuate from day to day, being higher in the afternoon than in the morning. So, who says that an elevated white blood cell means there must be an infection?