Diagnosis and tests

Bone marrow aspiration and biopsy

Hearing “we need to take a bone marrow sample” frightens many people. Yet the procedure is short, is done under local anaesthetic and is the most important step towards understanding the leukemia precisely. This topic explains how the procedure goes, how to prepare, what to expect afterwards and which tests are run on the sample.

Last updated: 30 September 2026~6 min read

A translucent hip bone on a dark navy background; inside its spongy interior the marrow glows softly in warm red and teal tones, with a few blood cells floating nearby. — **Figure 1.**Concept: blood cells are made in the bone marrow inside the hip bone.

01Short answer

Because leukemia starts in the bone marrow, a marrow sample is usually needed to confirm and refine the diagnosis. The sample is taken in two ways, most often in the same session: in an aspiration, a thin needle draws liquid marrow into a syringe; in a biopsy, a slightly thicker needle removes a small core of bone and marrow. The back of the hip bone (the iliac crest) is used most often; if only an aspiration is needed, the breastbone may be used. The procedure is done under local anaesthetic, a mild sedative can be offered, and children and teenagers often have sedation. The aspirate is used for a smear, flow cytometry, cytogenetics and molecular tests; the biopsy shows the structure of the marrow and how densely it is packed with cells. Serious complications are very rare. Some results are ready within days, while genetic results take longer. During treatment the procedure may be repeated to assess the response.

02Simple explanation

Bone marrow is the soft tissue inside large bones where blood cells are made. Leukemia starts here, so doctors want to look at the “source” — a blood test only shows the cells that have spilled into the blood.

An aspiration draws a little of the liquid part of the marrow into a syringe through a thin needle. This is the moment you are most likely to feel: a few seconds of pulling or sharp pain, which then passes.

A biopsy takes a small piece of bone and marrow with a slightly thicker needle. This piece shows the “architecture” of the marrow — how densely the cells are packed and how the tissue is organised.

The appointment usually takes 20–30 minutes, while taking the sample itself lasts only a few minutes. The skin and the surface of the bone are numbed; if you feel very anxious, ask about a sedative in advance.

Afterwards the area may ache or bruise for a few days. If you get a fever, increasing pain, redness, swelling or bleeding, let your care team know. Writing your questions down beforehand is a good way to ease anxiety.

03Scientific explanation

Where and how: according to the ACS, samples are usually taken from the back of the hip bone; if only an aspiration is planned, it may be taken from the breastbone. The skin and bone surface are numbed with a local anaesthetic; even so, most people feel brief pain during the aspiration. The biopsy is usually done straight after the aspiration with a slightly larger needle, and pressure is then applied to prevent bleeding. According to MedlinePlus, the samples themselves take about ten minutes to collect; Cancer Research UK notes that the whole test takes around 30 minutes and that children and teenagers often have sedation.

What is done with the aspirate? A smear is made from the liquid marrow and the cells are counted (the blast percentage), while the same sample is sent for flow cytometry (immunophenotype), cytogenetics (karyotype, FISH) and molecular tests (PCR, NGS). That is why the doctor may draw several syringes. The ACS notes that chromosome analysis requires the cells to grow in the lab, which can take about a week, while FISH results often come back sooner.

Why is a biopsy needed? A trephine biopsy shows the cellularity of the marrow, the structure of the tissue and any fibrosis (scarring). Sometimes no fluid can be drawn during the aspiration — this is called a “dry tap”, and in that case the biopsy is especially important. According to the NCI, in hairy cell leukemia the marrow is usually fibrotic and not easily aspirated; this disease can often also be diagnosed with flow cytometry of the blood.

During treatment: according to the ACS, marrow tests are repeated to see how the leukemia is responding to treatment. For example, under the 2022 ELN recommendations, complete remission in AML requires, among other criteria, fewer than 5% blasts in the marrow and recovery of blood counts; MRD can also be measured in these samples. Rare complications after the procedure include prolonged bleeding, infection and lasting pain (MedlinePlus).

04What happens in the body?

Preparing: what to know

If you take blood thinners or aspirin, tell your doctor in advance. If you will have a sedative, it is best to have someone take you home and not to drive for 24 hours. Wear comfortable clothes and write down your questions.

During the procedure

You usually lie on your side or your front. The doctor cleans and numbs the skin, then passes the needle into the bone. At the moment of aspiration there may be a brief pulling pain; during the biopsy you will feel pressure. Breathing calmly and talking with the staff can help.

Two translucent shapes side by side on a dark navy background: on the left a small drop of fluid full of glowing cells, on the right a thin cylindrical piece of bone with a visible spongy structure. — **Figure 2.**An aspiration yields liquid marrow, while a biopsy yields a small core of bone and marrow.

One sample — many tests

The marrow collected is shared between several laboratories: microscopy, flow cytometry, cytogenetics and molecular tests. This way a single procedure provides the information needed for the diagnosis, for defining the type of leukemia and for choosing treatment.

Delicate streams of light spreading in four directions from a glowing cluster of cells in the centre of a dark navy background, ending in silhouettes of a cell, coloured marker dots, a chromosome and a DNA helix. — **Figure 3.**A single marrow sample is shared between several tests — from the microscope to genetics.

After the procedure

You are usually advised to keep the dressing dry for a day and avoid heavy physical effort. Ask your doctor which painkiller is safe for mild pain — some medicines, such as aspirin, can increase the risk of bleeding.

While you wait for results

Microscopy results are sometimes ready in a day or two, while genetic results can take from several days to several weeks. Waiting is hard. Ask in advance which result will come when, and who will explain it to you and how.

05A bone marrow test step by step

Four steps — from preparation to results.

1PreparationMedicines, sedation and questions are discussed.

2NumbingThe skin and bone surface are numbed.

3Aspiration and biopsyLiquid marrow and a small bone core are taken.

4LaboratoryMicroscopy, flow cytometry, cytogenetics, molecular tests.

DiagnosisWhether leukemia is present, and which type.

Risk and targetsGenetic changes guide treatment.

Response checkRemission and MRD during treatment.

06Aspiration and biopsy: what is the difference?

	Aspiration	Biopsy (trephine)
What is taken?	Liquid marrow	A small core of bone and marrow
What does it show?	Cell types, blast percentage	Cellularity, structure, fibrosis
Which tests?	Smear, flow cytometry, cytogenetics, PCR/NGS	Histology, immunohistochemistry
How it feels	A brief pulling pain	A feeling of pressure
Time to result	Hours to weeks (depends on the test)	Usually a few days
Special case	A “dry tap” can happen	Especially important if no aspirate is obtained

* Timings vary between clinics and types of test. Ask your hematologist which tests will be done in your case and when the results will be ready.

07Key terms

Bone marrow: The soft tissue inside bones where blood cells are made.
Aspiration: Drawing liquid marrow into a syringe through a thin needle.
Trephine biopsy: Removing a small core of bone and marrow with a thicker needle.
Iliac crest: The upper back edge of the hip bone — the most common sampling site.
Local anaesthetic: Medicine that numbs only a specific area.
Sedation: Medicine that calms you and makes you drowsy.
Cellularity: How densely the marrow is packed with cells compared with other tissue.
Fibrosis: An increase in connective tissue in the marrow (scarring).
Dry tap: When no liquid marrow can be drawn during an aspiration.
Remission: The disappearance of signs of leukemia after treatment.

08Key points

Leukemia starts in the marrow, so a marrow sample is the key test.
Aspiration and biopsy are usually done in the same session.
The back of the hip bone is used most often.
Local anaesthetic is used, with sedation if you wish.
Many tests are run on one sample.
The biopsy shows the structure of the marrow and fibrosis.
Serious complications are very rare.
During treatment the procedure may be repeated to assess response.

09Frequently asked questions

Is it very painful?

The skin and bone surface are numbed, but a brief sharp or pulling pain during the aspiration is common. It usually lasts a few seconds. If you are worried, ask in advance about sedation or other ways to manage pain.

Is the sample taken from the spine?

No. A bone marrow sample is usually taken from the back of the hip bone, and the spinal cord is not touched. Taking spinal fluid (a lumbar puncture) is a completely different procedure and is only done in certain situations.

How will my child cope with this procedure?

Children and teenagers often have sedation or a short general anaesthetic so they do not feel discomfort during the procedure. A calm, honest explanation suited to your child’s age helps.

When will the results be ready?

Microscopy results are often ready in a day or two, and flow cytometry can also be quick. Chromosome and molecular tests can take from several days to several weeks. In urgent cases treatment may start before all the results are in.

When should I call my doctor?

If you have a fever, increasing pain, redness, swelling, or bleeding or discharge from under the dressing, tell your care team straight away.

How many times will this procedure be repeated?

That depends on the type of leukemia and the treatment plan. In acute leukemias the marrow test is usually repeated at certain stages of treatment to assess the response and MRD. Your hematologist will explain the schedule.

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

How will the bone marrow test be done, and how long will it take?
Will I get pain relief or sedation?
What should I watch for after the procedure?
When will the results be ready, and who will explain them?

My questions

12Sources

MedlinePlus (U.S. National Library of Medicine). Bone Marrow Tests
MedlinePlus Medical Encyclopedia. Bone marrow biopsy
MedlinePlus Medical Encyclopedia. Bone marrow aspiration
National Cancer Institute (NCI). NCI Dictionary of Cancer Terms: bone marrow aspiration
National Cancer Institute (NCI). NCI Dictionary of Cancer Terms: bone marrow biopsy
National Cancer Institute (NCI). Adult Acute Myeloid Leukemia Treatment (PDQ®) — Patient Version
National Cancer Institute (NCI). Hairy Cell Leukemia Treatment (PDQ®) — Health Professional Version
American Cancer Society. Tests for Acute Myeloid Leukemia (AML)
American Cancer Society. Tests for Acute Lymphocytic Leukemia
Cancer Research UK. Bone marrow test
Macmillan Cancer Support. Bone marrow biopsy
Testing.com. Bone Marrow Aspiration and Biopsy: What to Know
Blood (American Society of Hematology), 2022. Diagnosis and management of AML in adults: 2022 recommendations from an international expert panel on behalf of the ELN

Medical disclaimerThis information is for educational purposes only and does not replace medical advice.

Last updated: 30 September 2026← Back to the list

Open the interactive site →