The main indicators commonly used in blood tests for pneumonia are routine blood tests, C-reactive protein, Mycoplasma pneumoniae, and calcitoninogen. Mycoplasma pneumoniae, if IgM is positive, the presence of mycoplasma infection is considered. The presence of bacterial infection is also considered if the percentage of leukocytes and neutrophils is elevated, or if the percentage of leukocytes and neutrophils is decreased, a viral infection may be present. If the calcitonin index is high, bacterial infection is also considered, but if the calcitonin index is not high, viral infection may be present or there is no infection. The diagnosis of pneumonia is mainly based on the patient’s symptoms and imaging. Pneumonia can be diagnosed if there is a new faint or solid shadow in the lung with or without pleural effusion on CT or X-ray, and if the patient has symptoms of acute infection, such as fever and cough.