Bone marrow aspirate

  • A bone marrow aspirate (bone marrow test) is where a doctor uses a needle to take a sample of marrow from inside the bone. The sample is usually taken from the bones above the buttocks, which is the back of the pelvis. This procedure is very safe and is usually done under general anaesthetic.

    Why does my child need a bone marrow test?

    Bone marrow is responsible for making the three main types of blood cells: the red blood cells that carry oxygen to the body's organs; the white blood cells that help fight infection; and the platelets that help with blood clotting to stop bleeding when someone has cut themselves or is injured.

    A bone marrow test is needed to see how young blood cells are forming and if the marrow contains abnormal cells. It is an important test to help diagnose and monitor treatment in a number of medical conditions.

    What to expect

    Before the test

    Your child will need to fast (not have any food or drinks) before the test as they will be given a general anaesthetic (medicine that makes them go to sleep).

    If you are coming into hospital from home, you will be told what time your child should stop eating and drinking.

    Feel free to ask the doctor performing the test any questions you may have. The doctor may be from the haematology department and is not usually your child's treating specialist.

    During the test

    You may come in to the theatre area with your child until they are asleep. Your child will be positioned on their side.

    After the general anaesthetic is given, a needle is inserted into the back of the pelvis bone and a sample of marrow is collected. Occasionally, a different aspirate site may be used – you will be told if this will be the case for your child.

    Bone marrow aspirate

    Sometimes a thin core (sample) of bone called a trephine is also needed. A trephine biopsy usually takes a few minutes longer. In addition to the general anaesthetic, a local anaesthetic will also be used with a trephine biopsy to reduce any discomfort afterwards.

    Usually the bone marrow test takes less than half an hour.

    What are the risks?

    Every anaesthetic carries a very small risk of complication, which will be explained to you by the anaesthetist (doctor giving the anaesthetic).

    The bone marrow test may result in some minor bruising. The risk of serious complications (such as bleeding, infection and needle breakage) is extremely low. 

    Care at home

    Most children are able to continue with a normal day's activities after the bone marrow test.

    If your child is in nappies or there has been any bleeding, they will have a dressing to cover the aspirate site. You should take this dressing off the next day. Often this is easiest done at bath time.

    If your child is uncomfortable or has any pain in their lower back, you can give them some paracetamol (see our fact sheet Pain relief for children). 

    If your child shows any signs of infection around the area of the test (e.g. redness or warmth), or you are worried for any reason, call your child's treating hospital.

    Key points to remember

    • A bone marrow aspirate is a very important test needed to examine how young blood cells are formed.
    • It is a very safe procedure.
    • It is usually done under a general anaesthetic.
    • Ask the doctor performing the test any questions you may have.

    For more information

    Common questions our doctors are asked

    Will the bone marrow test hurt?

    When under general anaesthetic, your child will not have pain during the procedure. If they are awake, staff will do everything they can to minimise discomfort. They are likely to experience some discomfort, bruising and mild pain when they wake from their anaesthetic, but this will usually respond to simple pain relief.

    If your child needs ongoing bone marrow tests, talk to your child's doctors or nurses about a comfort plan, which can help to prevent anxiety about the procedure.

    When will I get the results?

    The samples collected require processing in the laboratory before they are looked at under a microscope. Bone marrow test results are usually available within one to two days, and a trephine biopsy will be available within two to three days. Other special tests may take longer. Your child's specialist will give you the results as soon as possible.

    Developed by The Royal Children's Hospital Haematology department and Comfort Kids. We acknowledge the input of RCH consumers and carers.

    Reviewed July 2018.

    This information is awaiting routine review. Please always seek the most recent advice from a registered and practising clinician.

    Kids Health Info is supported by The Royal Children’s Hospital Foundation. To donate, visit


This information is intended to support, not replace, discussion with your doctor or healthcare professionals. The authors of these consumer health information handouts have made a considerable effort to ensure the information is accurate, up to date and easy to understand. The Royal Children's Hospital Melbourne accepts no responsibility for any inaccuracies, information perceived as misleading, or the success of any treatment regimen detailed in these handouts. Information contained in the handouts is updated regularly and therefore you should always check you are referring to the most recent version of the handout. The onus is on you, the user, to ensure that you have downloaded the most up-to-date version of a consumer health information handout.