Bone marrow test - information for young people

If you come to Great Ormond Street Hospital (GOSH) for a bone marrow test (or biopsy) your doctors will take a sample of your bone marrow that they can then look at closely under a microscope. 

Bone marrow is the spongy tissue inside your bones that produces new blood cells. A bone marrow test (or biopsy) is when doctors take a sample of your bone marrow that they can then look at closely under a microscope. They might take a semi-liquid sample (known as an aspirate) or a solid sample (known as a trephine).

A doctor may want to look at your bone marrow to find out about the different types of cells (and how many of these cells there are) in your blood. This can help them learn more about your condition or see how well your body is responding to treatment.

What happens before the test?

You will have received a letter from the hospital with your appointment details, including any instructions about preparing for the test.

As bone marrow tests are usually carried out under general anaesthetic, you will need to avoid food and drink for a few hours beforehand. If you don’t, your test may be delayed or even cancelled.

When you arrive at the hospital, the doctor will talk to you in more detail about the test and you will be able to ask them any questions you might have.

You should also tell them if you have any allergies.

During the test

You will meet an anaesthetist before the test and they will explain what will happen and answer any questions you might have.

Once you are fast asleep, the doctor will insert a needle into your bone (usually the top of your pelvis) to take the sample. It might sound painful but while you’re under the anaesthetic you won’t feel a thing.

Every anaesthetic carries a risk, but this is small. Anaesthetists are highly trained doctors who look after you before, during and after the test.

After the test

You’ll probably feel sleepy after the test, so you’ll have to stay on the ward for a few hours until you wake up properly.

Try to drink plenty of fluids and have something to eat when you don’t feel sick.

You might also have a headache, sore throat, feel dizzy, feel sick and/or vomit.

These symptoms shouldn’t last very long – a nurse will be with you to give you medicine to help and make sure you are comfortable before you are taken back to your ward.

The doctor will put a plaster on your skin where the test was carried out. You will need to keep the plaster on for 24 hours after the test, but this shouldn’t stop you being able to have a bath or shower if you want.

The area around the biopsy site may also be sore and bruised. Taking painkillers like paracetamol will help. Make sure you follow the instructions on the bottle unless a member of the medical staff advises you otherwise.

Going home

You should be able to go home the same day as the test, and be back at school the day after. Take it easy though, and try to avoid PE or other sports for at least a week.

Ask your parents to contact the hospital if:

  • the biopsy site bleeds
  • the biopsy site oozes a lot of fluid
  • you are finding it difficult to drink plenty of fluid

Further information and support

Talk to your doctor or nurse about the bone marrow test.


You will receive the results of the biopsy as soon as possible.

Last review date:
February 2024