High blood count in children is a colloquial term that usually refers to a high white blood cell count. A high white blood cell count can be caused by bacterial infections, leukemia, medications, and certain physiological factors. 1. Bacterial infection: This is one of the most common causes of high white blood cell counts and is usually combined with elevated ultrasensitive C-reactive protein, which manifests itself as fever. 2. Leukemia: When white blood cells are significantly elevated, the possibility of leukemia should be ruled out. Leukemia is usually accompanied by changes in platelet and red blood cell counts. 3. Pharmacological elevation: When children use drugs such as glucocorticosteroids, there will be an increase in the number of white blood cells in the blood. 4. Physiological: A high white blood cell count in a newborn baby within 3 days of birth is often physiological. Or due to the child’s intense exercise, violent mood swings, vomiting, etc., may also appear elevated white blood cells. There are other causes of high blood counts in children, so it is recommended to seek medical attention to identify the cause and cooperate with the doctor if necessary.