Lumbar puncture

A lumbar puncture is a test to check the fluid that circulates round the brain and spinal cord. This is called the cerebrospinal fluid or CSF.

Why you might have this test

A lumbar puncture can check for cancer cells or for infection in the CSF.

Doctors remove some of the CSF to test for cancer cells. They use a needle to take a sample of the CSF from your lower back.

Diagram showing how you have a lumbar puncture

You normally have this test in the outpatient department under local anaesthetic. This means you are awake but the area is numb. 

This video explains how you have a lumbar puncture and the side effects you might have. 

Preparing for your lumbar puncture

Check your appointment letter for how to prepare for your lumbar puncture test. You are usually able to eat and drink before your test. Take your medications as normal. 

Children and some adults may have this under a general anaesthetic (GA) Open a glossary item or with sedation. You have to stop eating and drinking for some time before the test if you're having a GA. 

What happens

Your doctor will give you information about the procedure and ask you to sign a consent form. This is a good time to ask any questions you may have.

A staff member asks you to take off your upper clothing and put on a hospital gown.

You usually lie on your side with your knees tucked up into your chest. It's important to stay as still as you can during the test, so make sure you are comfortable before it starts.

The doctor or nurse drapes some sterile covers over you. Then they clean the area with antiseptic fluid, which can feel cold.

You have an injection of anaesthetic into the area, this can sting for a few seconds. When the area is numb, the doctor or nurse puts the lumbar puncture needle in through the skin. It goes into the small of your back and into the space around the spinal cord. You might feel some pressure when the needle goes in.

Once it's in the right place, the fluid drips out into a pot. This only takes a few seconds.

Your doctor or nurse takes the needle out and puts a dressing or plaster on your back.

The whole test takes about 20 to 30 minutes. It can be uncomfortable but it's not usually painful.

After your lumbar puncture

You lie flat for an hour or so after the test.

Tell your doctor or nurse if you have a headache, so they can give you some pain killers. Lying flat and drinking plenty of fluids may relieve your headache. This may last for a couple of days so make sure you have pain killers to take home. 

You will have a dressing on the skin where they did the test. You usually remove this the next day.

You can usually go home the same day. 

Possible risks

A lumbar puncture is a very safe procedure but your nurse will tell you who to contact if you have any problems after your test. Your doctors will make sure the benefits of having a lumbar puncture outweigh these possible risks.


If your headache doesn't get better contact your hospital team.


You might have lower back pain for a couple of days after the test. Contact your hospital team if the pain is severe.


You usually have a small spot of blood on the dressing on your back. Contact your hospital team if you have bleeding for more than 15 minutes.


This is very rare. You may have a high temperature or generally feel unwell. 

Contact the hospital straight away if you:

  • have a high temperature
  • are being sick
  • are sensitive to bright light
  • have tingling or numbness in your legs
  • have a severe headache

Getting your results

The fluid is sent to the laboratory and examined under a microscope for cancer cells.

It can take time for test results to come through. How long will depend on why you're having the test. It could be a day or two but can be up to a couple of weeks.

If you have not had your results a few weeks after your test, you could contact your doctor to chase your results for you.

Waiting for results can be an anxious time. It might be helpful to talk to someone close to you. 

You can also contact the Cancer Research UK nurses on freephone 0808 800 4040. The lines are open from 9 to 5, from Monday to Friday.

More information

We have more information on tests, treatment and support if you have been diagnosed with cancer.

Last reviewed: 
18 Dec 2018
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