A lumbar puncture is where a thin needle is inserted between the bones in your lower spine. It should not be painful, but you may have a headache and some back pain for a few days.

It's carried out in hospital by a doctor or specialist nurse.

A lumbar puncture may be used to:

• take a sample of fluid from your spinal cord (cerebrospinal fluid) or measure the fluid's pressure – to help diagnose a condition
• inject medicine – such as painkillers, antibiotics or chemotherapy
• inject a spinal anaesthetic (epidural) – to numb the lower part of your body before an operation
• remove some fluid to reduce pressure in the skull or spine

Your doctor or nurse should explain what's going to happen and why you need a lumbar puncture.

A few days or weeks before the test:

• you may have a CT scan or MRI scan – to make sure you need the lumbar puncture and it's safe to have one
• let the hospital know if you're taking blood-thinning medicine (anticoagulants) – such as warfarin

On the day:

• you can eat, drink and take medicine as normal
• you'll be asked to sign a consent form
• you'll usually need to undress and change into a hospital gown before the procedure – you might also want to use the toilet

What happens during a lumbar puncture

The doctor or nurse will:

1. Clean your skin and numb the area with local anaesthetic (you'll be awake during the procedure). Children may also be given medicine to help them relax and keep still.
2. Insert a thin needle through the skin, between 2 bones in the lower part of your spine. This should not be painful, but you may feel some pressure.
3. Remove the needle once the procedure is finished and apply a small plaster or dressing.

A lumbar puncture takes around 30 to 45 minutes, but you'll need to stay lying down at the hospital for at least another hour while the nurses monitor you.

You'll be able to go home the same day if you feel well enough, but you would not be able to drive yourself home.

The doctor or nurse who performs the lumbar puncture can often tell you some of the results straight away and explain what they mean.

You may need to wait for at least 48 hours for the full results. Some laboratory test results are available within a couple of hours in an emergency.

A lumbar puncture is generally a safe procedure and serious side effects are uncommon.

The most common side effects are:

• headaches, which can last for up to a week – you'll be given painkillers at the hospital if you need them
• swelling and lower back pain where the needle was inserted – this should get better on its own after a few days and is normally nothing to worry about

While you're recovering from a lumbar puncture: