Fever in leukemia is characterized by irregularity and uncertainty of fever type, which may be low or as high as 39~40℃. The causes and manifestations of fever are explained below. 1. Leukemia is usually caused by abnormal white blood cells and decreased immune function. If the patient has fever due to hypermetabolism and destruction caused by the increase of leukocytes, it is often called tumor fever, and the patient may also have fever due to the decrease of immune function and secondary infection, which is called infection fever. 2. Fever of leukemia manifests itself as irregular and variable, which can be low or as high as 39~40℃. Fever caused by leukemia is generally not easy to get well and lasts for a long time, even if the fever goes down, it will continue to have fever soon, and at the same time, there will be different degrees of bleeding gums, mucous membrane bleeding and other symptoms. Leukemia patients with fever symptoms should promptly consult the doctor, under the guidance of the doctor to improve the examination, receive the correct treatment, so as not to delay the condition.