Diagnosis of meningitis is based on a medical history, a physical exam, and tests.

Lumbar puncture

Your doctor will almost always do a lumbar puncture test (also known as a spinal tap) if he or she thinks you have meningitis.

A lumbar puncture takes samples of the fluid around the spine and brain, known as cerebral spinal fluid (CSF). A culture of the spinal fluid is done to check for organisms known to cause illness. It often takes several days to several weeks to get results from a spinal fluid culture. But other tests also can be done on the spinal fluid to determine which organism is causing the infection. The results of these tests may be ready before the results of a culture.

Other tests

A health professional also may do the following tests to see if there are other causes for your symptoms:

• Computed tomography (CT scan) or magnetic resonance image (MRI), to look for swelling of brain tissue or for complications such as brain damage
• Urine test, to check for infection in the urinary tract
• Chest X-ray, to check for lung infections
• Blood culture, to check for infections
• Biopsy of a skin rash