Fever can be seen in leukemia patients, but there are many causes of fever, and leukemia cannot be diagnosed based on the duration of fever. The diagnostic criteria of leukemia mainly include clinical manifestations, blood test, bone marrow examination, etc., as follows. 1. Clinical manifestations: leukemia is mostly manifested by fever, nosebleed, bleeding gums, bruises on the skin and so on. 2. Blood test: The range of blood test changes is large, and there are mostly different degrees of anemia. The total number of white blood cells may be very high or very low. 3. Bone marrow examination: Bone marrow examination is carried out by taking bone marrow specimen through bone marrow aspiration, which is an important basis for confirming the diagnosis of leukemia. In leukemia, bone marrow proliferation is active, with more than 30% of primitive and naïve cells, usually more than 50%, and in rare cases, there may be low proliferation or no naïve cells. Once fever and nosebleed don’t get better, you should go to the hospital in time to find out the cause and get treatment under the doctor’s guidance.