Bone Marrow Aspiration

This is an examination in which a needle is inserted into a bone and a portion of the marrow in the bone is removed. This test confirms the diagnosis of anemias, leukemia, or myelomas. It helps determine the cause of decreased blood cells and deficient iron stores. It documents the process of metastasis if there has been a tumor which has spread to bone. It also helps study tumor staging, especially in lymphomas.

There are two methods for sampling bone marrow, an aspirate and a biopsy. The bone marrow, a soft fatty tissue found inside the body's larger bones, is often described as being like a honeycomb – it is a fibrous network filled with a liquid containing cells in various stages of maturation, and "raw materials" such as iron, vitamin B12, and folate that are required for cell production. The bone marrow aspirate provides a liquid sample of cells that can be studied individually, and the biopsy collects a sample that preserves the marrow's structure and shows the relationships of bone marrow cells to one another and the relative amount of marrow cells compared to fat (cellularity).

Red blood cells (RBCs), platelets, and five different types of white blood cells (WBCs) are produced in the marrow as needed, with the number and type of cell being created at any one time based on the use of cells, loss, and a continual replacement of old cells.

The bone marrow biopsy and aspiration provide information about the status of and capability for blood cell production. They are not routinely ordered and in fact the majority of people will never have one done. A marrow aspiration or biopsy may be ordered to help evaluate blood cell production, to help diagnose leukemia, to help diagnose a bone marrow disorder, to help diagnose and stage a variety of other types of cancer (to determine spread into the marrow), and to help determine whether a severe anemia is due to decreased RBC production, increased loss, abnormal RBC production, or to a vitamin or mineral deficiency or excess. Conditions that affect the marrow can affect the number, mixture, and maturity of the cells, and can affect its fibrous structure.


  • No special preparation is needed. The bone marrow aspiration or biopsy procedure is performed by a caregiver. Both types of samples may be collected from the hip bone (pelvis), and marrow aspirations may be collected from the breastbone (sternum). In children, samples may also be collected from a vertebrae in the back or from the thigh bone (femur).

  • The most common collection site is the top ridge of the hip bone (iliac crest). Before the procedure, your blood pressure, heart rate, and temperature are measured and evaluated to make sure that they are within normal limits. You may be given a mild sedative. You will be asked to lie down on your stomach or side. Your 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 is numb, the caregiver inserts a needle through the skin and into the bone. For an aspiration, the caregiver attaches a syringe to the needle and pulls back on the plunger. This creates vacuum pressure and pulls a small amount of marrow into the syringe.

  • For a bone marrow biopsy, the caregiver uses a special needle that allows the collection of a sample of bone and marrow. Even though your skin has been numbed, you may feel brief but uncomfortable pressure sensations during these procedures. After the needle has been withdrawn, a sterile bandage is placed over the site and pressure is applied. You will then usually be instructed to lie quietly until your blood pressure, heart rate, and temperature are normal. You may be instructed to keep the site dry and covered for 48 hours.

  • Complications from the bone marrow aspiration or biopsy procedure are rare, but some individuals may have excessive bleeding at the site or develop an infection.

  • Tell your caregiver about any allergies you have and about any medications or supplements you are taking prior to the procedure.


Cell type / Range (%)

  • Myeloblasts / less than 5

  • Promyelocytes / 1-8

  • Myelocytes

  • Neutrophilic / 5-15

  • Eosinophilic / 0.5-3

  • Basophilic / less than 1

  • Metamyelocytes

  • Neutrophilic / 15-25

  • Eosinophilic / less than 1

  • Basophilic / less than 1

  • Mature myelocytes

  • Neutrophilic / 10-30

  • Eosinophilic / less than 5

  • Basophilic / less than 5

  • Mononuclear

  • Monocytes / less than 5

  • Lymphocytes / 3-20

  • Plasma cells / less than 1

  • Megakaryocytes / less than 5

  • M/E ratio / less than 4

  • Normoblasts / 25-50

Normal iron content is demonstrated by staining with Prussian blue.

Ranges for normal findings may vary among different laboratories and hospitals. You should always check with your caregiver after having lab work or other tests done to discuss the meaning of your test results and whether your values are considered within normal limits.


Your caregiver will go over the test results with you and discuss the importance and meaning of your results, as well as treatment options and the need for additional tests if necessary.


It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.