You may do one or more of the following tests:

1. A chest X-ray looks for inflammation in your lungs. A chest X-ray is often used to diagnose pneumonia.

2. Blood tests, such as a complete blood count (CBC) see whether your immune system is fighting an infection.

3. Pulse oximetry measures how much oxygen is in your blood. Pneumonia can keep your lungs from getting enough oxygen into your blood. To measure the levels, a small sensor called a pulse oximeter is attached to your finger or ear.

4. A blood gas test may be done if you are very sick. For this test, your provider measures your blood oxygen levels using a blood sample from an artery, usually in your wrist. This is called an arterial blood gas test.

5. A sputum test, using a sample of sputum (spit) or mucus from your cough, may be used to find out what germ is causing your pneumonia.

6. A blood culture test can identify the germ causing your pneumonia and also show whether a bacterial infection has spread to your blood.

7. A polymerase chain reaction (PCR) test quickly checks your blood or sputum sample to find the DNA of germs that cause pneumonia.

8. A bronchoscopy looks inside your airways. If your treatment is not working well, this procedure may be needed. At the same time, your doctor may also collect samples of your lung tissue and fluid from your lungs to help find the cause of your pneumonia.

9. A chest computed tomography (CT) scan can show how much of your lungs are affected by pneumonia. It can also show whether you have complications such as lung abscesses or pleural disorders. A CT scan shows more detail than a chest X-ray.

10. A pleural fluid culture can be taken using a procedure called thoracentesis, which is when a doctor uses a needle to take a sample of fluid from the pleural space between your lungs and chest wall. The fluid is then tested for bacteria.