Fever in leukemia is mostly high, most of them are at 38°C, even to 39-40°C. To understand fever in leukemia, it is important to know the cause of fever in leukemia patients. This is because leukemia is a disease in which the white blood cells, or granulocytes, appear to make blood. Although patients have high white blood cells, these are white blood cells that have lost their normal function, and the role of normal white blood cells is mainly to engulf bacteria. The leukemia patient’s white blood cells are abnormal white blood cells that have lost their ability to engulf bacteria, so the leukemia patient has a low resistance. When the resistance is low, it is particularly easy to combine infections, especially infections in the parts of the body that are connected to the outside world, such as the respiratory tract, digestive tract, and urinary tract. Respiratory tract infections can lead to coughing, coughing up sputum, and even chest suffocation and shortness of breath. Gastrointestinal tract infections may include abdominal pain, diarrhea, and watery stools. Urinary tract infections can cause painful urination, urgency, and frequency of urination. Because leukemia patients have low resistance, infections are not easily controlled and fevers are more difficult to control and are longer and higher in temperature.