Fever starting at 12 o’clock every day (12 o’clock at noon or 12 o’clock at night) includes infectious factors (tuberculosis, bacterial infections, etc.) and non-infectious factors (tumors, immune system diseases, endocrine system diseases, etc.), which need to be analyzed specifically. 1. Infectious factors: Whether tuberculosis, bacterial, fungal, viral and other pathogenic infections, may appear every day at 12 o’clock fever, blood routine, PPD, chest X-ray and other related tests can assist in the definitive diagnosis. 2. Non-infectious factors: including tumors, immune system diseases (such as systemic lupus erythematosus, rheumatoid arthritis, etc.), endocrine system diseases (such as hyperthyroidism, etc.), will be accompanied by fever symptoms, may appear every day at 12 o’clock fever, tumor markers, antinuclear antibody spectrum, rheumatoid factor, thyroid function and other tests can assist in clear diagnosis. Regardless of the cause of fever starting at 12 o’clock every day, it is recommended to consult a doctor as early as possible to make a clear diagnosis in time to avoid delaying the condition.