Severe anemia does not usually cause fever. Severe anemia refers to hemoglobin <60g/L, hemoglobin concentration <30g/L is called extremely severe anemia. The main manifestations of weakness, pale skin and mucous membranes, quiet state can appear rapid heart rate, dyspnea and other symptoms, the system can have different manifestations. Generally, it does not cause fever. Different causes of anemia, clinical manifestations are also different, such as megaloblastic anemia can be accompanied by angular stomatitis, papillary atrophy of the tongue, etc., hemolytic anemia can be yellow staining of the skin and mucous membranes, strong tea-colored urine or soy sauce-colored urine, etc., iron-deficiency anemia can be heterophagia and so on. Severe anemia with leukopenia is accompanied by increased risk of various infections, and when fever occurs, the cause should be promptly identified in the hospital and standardized treatment.