The duration of treatment for low-grade fever in tuberculosis varies from person to person. Symptoms usually subside after 2 to 3 weeks of treatment. Tuberculosis is an infection of the lungs caused by Mycobacterium tuberculosis. Fever in tuberculosis is usually low at first, but it becomes obvious as the disease progresses. Typically, the fever is diurnal, that is, there is no fever in the early morning, and then the temperature rises gradually during the day and peaks in the evening or night. The fever subsides during sleep, but night sweats may occur. Fever and night sweats are more common in patients with progressive TB. How long a low-grade fever lasts in TB is related to treatment. It usually subsides after 2 to 3 weeks of treatment. Without proper treatment, the condition may worsen and the fever may last longer. Patients with tuberculosis generally have a good prognosis and can be cured as long as they are treated reasonably and regularly.