Low fever after 5 days of treatment for pneumonia can be caused by uncontrolled inflammation, the body’s immune system’s reaction against pathogens, and other lung diseases such as lung cancer, and should be treated according to the cause of the disease. 1. Inflammation is not fully controlled: low fever after 5 days of treatment may be due to the fact that the medication has not reached the course of treatment, inflammation is not fully controlled or resistance to antibiotics has developed. The program should be adjusted in time after comprehensive judgment. 2. Human immune system response: Fever is usually the immune response of human immune cells against pathogenic microorganisms and inflammatory exudates. After 5 days of pneumonia treatment, the pathogens in the body have not been cleared and the immune system continues to function, a low-grade fever will occur. 3. Other lung diseases: pneumonia patients with low fever after 5 days of treatment, there may also be a combination of tuberculosis, lung fungal infection or lung cancer caused by fever. After the diagnosis is clear, the treatment should be targeted. Pneumonia patients who have a low fever after 5 days of treatment should go to the hospital for examination to determine the specific cause of the disease and then carry out targeted treatment.