Low fever of 37℃ is not necessarily cancer, but may also be caused by inflammatory diseases and autoimmune diseases, which need to be clearly diagnosed and treated symptomatically. Clinically, many kinds of cancer can cause long-term low fever, such as acute leukemia, lymphoma, lung cancer, etc., mostly due to the growth of the tumor, causing inflammation and fever, or by the tumor necrotic tissues are absorbed by the body, leading to carcinogenic fever, which need to be diagnosed clearly through pathological examination, bone marrow examination, CT or MRI, etc., and be treated with surgery, radiotherapy, chemotherapy and other treatments. Other diseases, such as bronchitis, pneumonia, tuberculosis infection, Hashimoto’s thyroiditis, systemic lupus erythematosus, rheumatoid arthritis, etc., can also cause prolonged low-grade fever. Therefore, patients who suffer from prolonged low-grade fever need to go to internal medicine or oncology department for a comprehensive examination to clarify the cause of low-grade fever and cooperate with doctors to carry out the relevant treatment. Patients with prolonged hypothermia should pay attention to their diet, eat light and nutritious food, drink more water, have a reasonable rest and improve the body’s ability to resist diseases.