Whether or not a high fever is leukemia cannot be generalized because other diseases can also present with a high fever, so patients need a clear diagnosis based on clinical symptoms and signs. A high fever that does not go away is when the body temperature exceeds 39°C, lasts for a long time, is not easily relieved, and can usually be caused by a variety of reasons. Fever is one of the most common symptoms of leukemia. The main cause of high fever in patients with leukemia is infection, which can be accompanied by sepsis and septicemia in severe cases and requires active anti-infection treatment. In addition to leukemia, typhoid fever, bacterial dysentery, influenza, epidemic B encephalitis and many other diseases can also cause high fever that does not go away. If the fever is caused by bacterial infection, it needs to be treated with antibiotics; if the fever is caused by viral infection, sometimes antiviral drugs can be used together with antipyretic drugs such as acetaminophen and ibuprofen. When a patient has a high fever that does not go away, he or she should go to the fever clinic or the hematology department of the hospital in a timely manner and undergo blood routine, bone marrow biopsy and blood biochemistry examinations to make a clear diagnosis and then provide active symptomatic treatment.