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Lumbar Puncture
A lumbar puncture takes a sample of the fluid around the spinal cord and brain (cerebrospinal fluid) using a needle in the lower back, to help diagnose conditions such as meningitis or bleeding.
Quick answer
Lumbar Puncture: what it is and what the results mean
A lumbar puncture (spinal tap) uses a fine needle inserted between the bones of the lower spine to collect cerebrospinal fluid (CSF) — the clear fluid that surrounds the brain and spinal cord. It can also measure the pressure of this fluid.
- Why it is done: It is used to diagnose infections such as meningitis and encephalitis, bleeding around the brain, inflammatory conditions like multiple sclerosis, and raised or low fluid pressure, and sometimes to give medicines or remove fluid.
- Understanding results: The fluid is examined for cells, protein, sugar, infection and other markers.
What it is
A lumbar puncture (spinal tap) uses a fine needle inserted between the bones of the lower spine to collect cerebrospinal fluid (CSF) — the clear fluid that surrounds the brain and spinal cord. It can also measure the pressure of this fluid.
Why it is done
It is used to diagnose infections such as meningitis and encephalitis, bleeding around the brain, inflammatory conditions like multiple sclerosis, and raised or low fluid pressure, and sometimes to give medicines or remove fluid.
What to expect
You curl up on your side or lean forward. Local anaesthetic numbs the skin, then a thin needle is passed between the spine bones to collect fluid; you may feel pressure. It takes about 30–45 minutes, and you rest afterwards.
Understanding the results
The fluid is examined for cells, protein, sugar, infection and other markers. Results, some available quickly and some after a few days, help confirm or rule out conditions and guide treatment.
Good to know
Risks and limitations
The most common effect is a headache afterwards, which is usually eased by lying flat and fluids. Less common risks include back pain, bleeding or infection. It is avoided if there are signs of dangerously raised pressure in the head.
Education and reference only. This explains the test in general terms and is not medical advice. Always follow the specific instructions from the team arranging your test, and discuss your results with your clinician.
Answers
Lumbar Puncture: frequently asked questions
Why might I get a headache after a lumbar puncture?
A headache can occur because a small amount of fluid leaks from the puncture site, easing when you lie flat. Drinking fluids and rest usually help, and persistent headaches can be treated.
Is a lumbar puncture dangerous?
It is generally safe when done by trained staff. Serious complications are rare, and checks are made beforehand to ensure it is safe, such as excluding dangerously raised pressure in the head.
Related tests
Other other investigations
Sources
Where this is drawn from
- NHS — Tests and treatments
- NICE — diagnostic guidance
- Relevant royal college / professional body
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