A physician can diagnose pneumonia by tapping the chest and listening with a stethoscope to the sound produced. Tapping the chest of a healthy person produces a resonant sound because of the air contained in the lungs. In a person with pneumonia, the air spaces of the lungs become filled with fluid, and tapping produces a dull, flat sound. The diagnosis of pneumonia is confirmed by taking an X-ray picture of the chest.

 To determine the cause of pneumonia, a physician takes a sample of the patient's sputum. Analysis of the sputum in the laboratory may identify the particular kind of microorganism causing the infection. Identification of the cause of pneumonia is important in determining treatment.

 Antibiotics can cure bacterial pneumonia and speed recovery from mycoplasma pneumonia and PCP. Antibiotics rarely have an effect on pneumonia caused by viruses. However, patients with viral pneumonia often receive antibiotics to prevent bacterial pneumonia from developing during the course of their illness. In addition to drug treatment, a patient with pneumonia should stay in bed, eat healthy meals, and drink large amounts of liquids. Medication may be given to relieve chest pain and violent coughing, and oxygen may be administered if the patient has difficulty breathing. A vaccine is available that confers immunity against pneumococcus. The vaccine is given to people most at risk for developing pneumonia—those over the age of 65 and those with chronic heart, lung, or liver disease.