A low-grade fever is not necessarily an early sign of cancer. Diseases causing fever can be categorized into infectious fever and non-infectious fever, not only cancer can cause fever. 1. Infectious fever: Functional fever caused by healing after infection, various viruses, bacteria, parasites and other original infections have been cured but the thermoregulatory function has not been restored. 2. Non-infectious fever (1) Blood diseases: leukemia, malignant histiocytes, etc. (2) Connective tissue diseases: systemic lupus erythematosus, rheumatoid arthritis, dermatomyositis, etc. (3) Metabolic diseases: drug fever, hemolytic reaction, serum sickness, etc. (4) Endocrine metabolic diseases: gout, hyperthyroidism, etc. (5) Thrombotic and embolic diseases: myocardial infarction, limb necrosis, pulmonary infarction, etc. (6) Intracranial diseases: cerebral hemorrhage, cerebral contusion, concussion, etc. (7) Skin lesions: ichthyosis, generalized dermatitis, etc. (8) Malignant tumors: fever may occur regardless of the type of malignant tumor. (9) Physical and chemical damage: fracture, extensive burns, etc. (10) Autonomic dysfunction: mainly hypothermia, such as summer hypothermia caused by malnutrition, physiologic hypothermia caused by mental stress, etc.. When low fever occurs, you should go to the hospital in time to find out the cause and target the treatment to prevent delaying the condition.