Also Known As
Bone Marrow Examination
Formal Name
Bone Marrow Aspiration and Biopsy
This article was last reviewed on
This article waslast modified on
April 25, 2018.
At a Glance
Why Get Tested?

To evaluate the number and appearance of blood cell precursors in the bone marrow; to evaluate the structure and adequacy of the blood cell-producing marrow; to help investigate or diagnose a disease or condition affecting the bone marrow or blood cell production

When To Get Tested?

When you are anemic without an obvious cause; when you have or are suspected of having a blood-related disorder or cancer that may be affecting blood cell production; sometimes when a health practitioner is investigating a fever of unknown origin, especially when you have a weakened immune system (immunocompromised)

Sample Required?

A bone marrow sample collected primarily from the hip bone (pelvis); sometimes collected from the sternum in adults or the tibia (shin bone) in infants

Test Preparation Needed?


You may be able to find your test results on your laboratory's website or patient portal. However, you are currently at Lab Tests Online. You may have been directed here by your lab's website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab's website or portal, or contact your healthcare practitioner in order to obtain your test results.

Lab Tests Online is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called "normal" values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

For more information, please read the article Reference Ranges and What They Mean.

What is being tested?

Bone marrow is the soft and sponge-like tissue found inside the body's larger bones that produces blood cells. Bone marrow aspiration and biopsy are procedures used to collect and evaluate bone marrow cells and structure.

Bone marrow has a honeycomb or sponge-like structure, consisting of a fibrous network that is filled with liquid. The liquid portion contains blood (hematopoetic) stem cells, blood cells in various stages of maturation, and "raw materials" such as iron, vitamin B12, and folate that are required for cell production.

The primary function of the bone marrow is to produce red blood cells (RBCs), platelets, and white blood cells (WBCs). The number and type of cell being produced at any one time is based on the cell function, blood loss, and a normal, continual replacement of old cells.

A bone marrow aspiration collects a sample of the fluid that contains cells so that they can be examined under a microscope and/or evaluated with other tests. A biopsy collects a cylindrical core sample that preserves the marrow's structure. The biopsy sample is evaluated to determine the relationships of bone marrow cells to one another and the overall cellularity – the relative ratio of marrow cells to fat and other constituents present in the sample.

Red Blood Cells (RBCs)
Red blood cells, also called erythrocytes, transport oxygen throughout the body. RBCs typically make up about 40-45% of the blood volume and usually survive in circulation for about 120 days. The marrow produces RBCs at a rate that replaces old RBCs that age and degrade or are lost through bleeding, striving to maintain a relatively constant number of RBCs in the blood.

White Blood Cells (WBCs)
There are five different types of white blood cells: lymphocytes, neutrophils, eosinophils, basophils, and monocytes. Each plays a different role in protecting the body from infection.

Platelets, also called thrombocytes, are cytoplasmic fragments of very big cells seen in bone marrow called megakaryocytes and are essential for normal blood clotting.

In the bone marrow, a stem cell undergoes development and differentiation to become one of these different types of blood cells. Those that differentiate into lymphoid cells subsequently develop into lymphocytes. Other precursors further develop and differentiate into granulocytes (neutrophils, eosinophils, basophils), monocytes, platelets, or red blood cells (erythrocytes).

The cells are released from the bone marrow into circulation when they are fully mature or near full maturity. Thus, the population of cells within bone marrow will typically include cells in various stages of development, from very immature to almost fully mature.

Bone marrow aspiration and/or biopsy as "tests" include both the collection of marrow samples and the evaluation of the cells and structure under the microscope.

  • A specialist microscopically examines slides of stained smears of the fluid from an aspiration. The cells are evaluated according to number, type, maturity, appearance, etc. and compared to those in the blood using results from a complete blood count (CBC) and blood smear.
  • The specialist also evaluates the structure and cellularity of the marrow sample from a biopsy.

For example, if leukemia is present, or another cancer has spread into the marrow, it can be diagnosed through these examinations, and the type and severity of the disease (the stage) can be established.

Depending on what condition(s) a health practitioner suspects or is investigating, a number of other tests may be performed on the marrow sample. A few examples include:

  • In the case of leukemia, tests to determine the type of leukemia may be done. These include special stains or the determination of antigenic markers (for example, immunophenotyping by flow cytometry) to provide information on the type of leukemia present.
  • Special stains may also be used to evaluate iron storage in the marrow and to determine whether an abnormal erythroid precursor with iron particles surrounding its nucleus (so-called ringed sideroblasts) is present.
  • A chromosome analysis and/or fluorescence in-situ hybridization (FISH) analysis may be ordered to detect chromosomal abnormalities in the case of leukemia, myelodysplasia, lymphoma, or myeloma.
  • Molecular tests such as BCR-ABL1 or JAK2 mutation may be performed on a sample of bone marrow to help establish a diagnosis.
  • Bone marrow may be cultured to look for viral, bacterial, or fungal infections that can cause a "fever of unknown origin." Certain bacteria and fungi can also be detected by special stains.

How is the sample collected for testing?

The bone marrow aspiration and/or biopsy procedure is performed by a doctor or other trained specialist. Both types of samples may be collected from the hip bone (iliac crest). Marrow aspirations are sometimes collected from the sternum (breastbone) of adults. In infants, samples may be collected from the tibia (shin bone). Sometimes, a bilateral iliac procedure is performed.

The most common collection site is the iliac crest (top ridge) of the back of the hip bone. Before the procedure, the patient's blood pressure, heart rate, and temperature are measured and evaluated to make sure that they are within normal limits, and some patients are given a mild sedative. The patient is then asked to lie down on his or her stomach or side for the collection, and the person's lower body is draped with cloths so that only the area surrounding the site is exposed.

The site is cleaned with an antiseptic and injected with a local anesthetic. When the site has numbed, the health practitioner inserts a needle through the skin and into the bone. For an aspiration, a syringe is attached to the needle to collect a small amount of marrow. For a bone marrow biopsy, a special needle is used that allows the collection of a solid core (a cylindrical sample) of marrow.

Even though the patient's skin has been numbed, the patient may feel brief but uncomfortable pulling and/or pushing pressure sensations during these procedures. After the needle has been withdrawn, a sterile bandage is placed over the site and pressure is applied. The patient is then asked to keep the collection site dry and covered for about 48 hours.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

Accordion Title
Common Questions
  • How is it used?

    Bone marrow aspiration and biopsy are procedures used to evaluate the blood cells within the bone marrow, as well as its structure. They are performed in conjunction with a complete blood count (CBC) and blood smear to provide information about the health of the bone marrow and capability for blood cell production, including red blood cells (RBCs), white blood cells (WBCs), and platelets.

    These are not routine tests, and the majority of people will never have them done. However, they are useful in helping to detect, diagnose, monitor and/or stage a number of diseases and conditions that can affect the bone marrow and blood cell production.

    A specialist who has expertise in the diagnosis of blood-related disorders performs the examination and evaluation of bone marrow samples. This process determines, for example:

    • The M/E ratio—this is short for myeloid/erythroid ratio. This calculation compares the number of myeloid cells (WBC precursors) to erythroid cells (RBC precursors).
    • Differential—determines whether cells in each lineage (WBC, RBC, platelet-producing cells) show orderly and complete maturation, and whether the cells are present in normal proportion to one another.
    • Presence of any abnormal cells, such as leukemic or tumor cells.
    • Cellularity—the volume of cells is compared to the volume of other components of the bone marrow, such as fat.
    • The structure of the bone marrow, including the sponge bone (trabecular bone)

    Using the information from the examination, a bone marrow aspiration and/or biopsy may be used to help:

    • Determine the cause of unexplained low or high blood cells counts, including too few or too many white blood cells (leukopenia or leukocytosis), red blood cells (anemia or polycythemia) or platelets (thrombocytopenia or thrombocythemia)
    • Identify the cause of abnormal or immature blood cells present in the blood, as detected by a CBC or a blood smear
    • Diagnose cancer originating in the bone marrow, e.g. leukemia, multiple myeloma
    • Diagnose other bone marrow disorders such as myelodysplastic syndrome (MDS)
    • Diagnose and stage a variety of other types of cancers, such as lymphoma, breast or lung cancer, that may involve or have spread to the bone marrow
    • Diagnose conditions that affect the marrow and its fibrous structure, such as myelofibrosis
    • Evaluate for a bone marrow infection if a person has a fever without an apparent cause (fever of unknown origin)
    • Determine if an individual has a chromosomal abnormality
    • Diagnose a disorder associated with iron storage that may cause stored iron to diminish

    If a person is being treated for a non-hematopoietic cancer, a bone marrow aspiration and/or biopsy may be ordered to evaluate the response to treatment to determine whether suppressed marrow function is beginning to return to normal.

    In addition to microscopic evaluation of the cells and structure, additional tests may be performed, depending on the purpose for testing:

  • When is it ordered?

    These tests are not routinely ordered. However, they may be ordered when results of other tests, such as a CBC and/or blood smear, are abnormal and a bone marrow examination is warranted.

    Bone marrow examination may be ordered when an individual's medical history, physical examination, and signs and symptoms suggest that the presence of a disease affecting the bone marrow.

    The tests may be ordered when staging certain cancers such as Hodgkin and Non-Hodgkin lymphomas or when it is suspected that other cancers have spread to the bone marrow.

    A bone marrow biopsy and aspiration may also be ordered at intervals when a person is being treated for a cancer other than a blood cancer to evaluate whether marrow function is being suppressed and, if it is, when its function begins to recover.

  • What does the test result mean?

    The laboratory report for these tests may include a description of the cells seen or the appearance of the bone marrow environment. Results from a complete blood count (CBC) and blood smear are usually included. Typically, the specialist provides an interpretation of the findings and any other details that might be important in the diagnosis, staging, or treatment of the disease.

    In many cases, this information can confirm or rule out a diagnosis and whether the bone marrow is affected by disease, but it can also point out the need for further investigation. For example, a patient with decreased red blood cells (RBCs) and no increase in reticulocytes may have aplastic anemia with suppressed RBC production in the marrow. An evaluation of the bone marrow may confirm this condition, but it does not necessarily tell the health practitioner whether it is due to a primary bone marrow disorder, radiation, exposure to certain chemicals, cancer, cancer treatment, or an infection.

    The health practitioner uses the information from the marrow evaluation and combines it with information from a clinical examination, medical history, blood tests, and a variety of other tests, such as imaging scans and X-rays, to reach a final diagnosis. It can be a straightforward process or it can be a complex diagnostic puzzle. Patients should stay involved in this process by talking to their health care provider before and after a bone marrow biopsy and/or aspiration, asking what the suspicions are, what kind of information is expected from the evaluation, and what follow-up tests might be indicated.

    A variety of disorders and conditions may be identified, monitored, and/or staged with this process. A few examples include:

    • Leukemia is a cancer of the blood cells. It results in the excessive production of one blood cell, resulting in the presence of large quantities of cells that do not function as normal ones do. When leukemic white blood cells (WBCs) crowd out RBC production in the bone marrow, the patient becomes anemic; when they decrease the number of platelets produced, they leave the patient vulnerable to excessive bruising and bleeding. Leukemia of red blood cell (erythroleukemia) in a similar fashion will crowd out WBC and/or platelet precursors.
    • Anemia is a low number of red blood cells and low hemoglobin. The marrow should increase the rate of RBC production whenever the number of RBCs in blood decreases. The increased rate of production continues until there is a sufficient number of RBCs in the blood or until marrow production capacity is reached. If the need exceeds capacity, then the number of RBCs in the blood will decrease and the individual will become increasingly anemic, with symptoms such as pallor, fatigue, and shortness of breath due to decreased oxygen-carrying capacity by the red blood cells. Anemia can also occur if the production of RBC in the marrow is suppressed.
    • Vitamin and mineral deficiencies, such as vitamin B12 and folate or iron deficiency, can lead to the production of large or small or abnormally shaped RBCs and result in specific types of anemia. Though these may be diagnosed by a bone marrow exam, they rarely are, and mainly are diagnosed by blood tests.
    • Diseases such as aplastic anemia that can affect the marrow's ability to produce an adequate number of each of the different blood cell types and release them into circulation. These diseases may affect the overall number of cells produced, the proportion of cells produced, and/or the function of the cells.
    • Some other bone marrow disorders may lead to a deficiency of one or more cell types (e.g., myelodysplastic syndrome) while others result in excess production of a specific type or of a specific clone of a cell—a single cell that reproduces without regulation (e.g., polycythemia vera, essential thrombocythemia).
    • Myelofibrosis is a disorder characterized by the overgrowth of the fibrous network found in the marrow, compressing cells and leading to changes in red blood cell shape and changes in the cell counts.
  • Is there anything else I should know?

    Complications from the bone marrow aspiration and/or biopsy procedure are rare, but occasionally people may have excessive bleeding at the collection site or develop an infection. Individuals should tell their health care provider about any allergies they have and about any medications or supplements they are taking prior to the procedure and should contact their health care provider promptly if they experience persistent or spreading redness or bleeding at the site, a fever, or increasing pain.

  • Will I be given general anesthesia for a bone marrow aspiration and/or biopsy?

    While you will be given a local anesthetic, an injection to numb the area of the collection site, general anesthesia is not usually necessary. However, you may be given a sedative before the procedure.

  • My report includes an M/E ratio. What is it?

    M/E ratio is short for myeloid to erythroid ratio. This is the number of myeloid cells compared to the number of erythroid cells within the bone marrow. Myeloid cells are those that mature into granulocytes (neutrophils, eosinophils, basophils), and erythroid precursor cells mature into red blood cells. This result is not diagnostic of any condition but is an additional piece of information that the health practitioner may use to help determine the health of the bone marrow. For example, in the case of bacterial infection, the M/E ratio will increase due to an elevated number of granulocytic cells, whereas in case of hemolytic anemia, the M/E ratio will decrease due to an increase in erythroid cells.

  • How does a bone marrow aspiration and/or biopsy compare with a bone marrow collection for donation?

    The collection process is similar, but the bone marrow donor goes through a physical and has blood tests done prior to the collection to make sure that he or she is healthy and that the person's sample will be compatible with the person to whom the marrow will be donated. The donor is usually put under general anesthesia during the collection because a larger amount of marrow must be obtained under sterile conditions. The sample is then processed, filtered, and given to the transplant recipient through a vein. The stem cells in the donor sample travel through the bloodstream to the recipient's marrow spaces and, if all goes right, begin to produce red blood cells, white blood cells, and platelets.

View Sources

Sources Used in Current Review

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