A bone marrow biopsy is a procedure that removes a small sample of the spongy tissue inside your bones so it can be examined under a microscope. It’s one of the most direct ways to evaluate how well your body is producing blood cells, and it plays a central role in diagnosing and monitoring blood cancers, anemias, and other conditions that affect the marrow. The procedure typically takes about 30 minutes and is performed with local anesthesia, often right in a doctor’s office or outpatient clinic.
What Bone Marrow Does
Bone marrow is the soft, fatty tissue found inside the center of most large bones. It functions as your body’s blood cell factory, producing red blood cells that carry oxygen, white blood cells that fight infection, and platelets that help with clotting. When something goes wrong with this production line, the effects show up in routine blood tests as abnormal cell counts. But blood tests alone can’t always explain why counts are off. A biopsy lets doctors look directly at the source.
Aspiration vs. Biopsy
The terms “bone marrow aspiration” and “bone marrow biopsy” are often used together because both are usually performed at the same time, during the same appointment. They collect different types of samples from the same site.
Bone marrow has both a liquid and a solid component. During the aspiration, a thin needle draws out a small amount of the liquid marrow. This fluid sample is useful for examining individual cells, their shapes, and their proportions. The biopsy follows immediately after, using a slightly larger, hollow needle designed to extract a small cylindrical core of solid bone and the marrow enclosed within it. This core sample preserves the architecture of the tissue, showing how cells are arranged and how densely packed the marrow is. Together, the two samples give a much more complete picture than either one alone.
Why It’s Ordered
Doctors order a bone marrow biopsy when blood test results raise questions that can’t be answered any other way. The most common reasons include:
- Unexplained blood count abnormalities. If your red cells, white cells, or platelets are consistently too high or too low without a clear cause, a biopsy can reveal what’s happening at the production level.
- Diagnosing blood cancers. Leukemia, lymphoma, and multiple myeloma often originate in or spread to the bone marrow. A biopsy confirms the diagnosis and identifies the specific type of cancer.
- Staging cancer. For cancers that may have spread, a marrow biopsy helps determine whether tumor cells have reached the bone marrow, which affects treatment decisions.
- Monitoring treatment. During chemotherapy or other cancer treatments, repeat biopsies track how well the marrow is responding, whether cancer cells are declining, or whether the disease has progressed.
- Evaluating iron storage and other disorders. Conditions like aplastic anemia, myelodysplastic syndromes, and certain infections can also be diagnosed through marrow examination.
What Happens During the Procedure
The biopsy is almost always taken from the posterior iliac crest, the large ridge of bone at the back of your hip. This site is preferred because the bone is close to the surface, easy to access, and rich in marrow. You’ll typically lie on your side or face down on an exam table.
The area is cleaned and numbed with a local anesthetic injected into the skin and down to the surface of the bone. Some facilities also offer light sedation through an IV if you’re particularly anxious or if the procedure is expected to be more involved. Once the area is numb, the doctor inserts the aspiration needle first, drawing out the liquid sample. This part often produces a brief, deep pulling or pressure sensation that the local anesthetic can’t fully block, since it comes from inside the bone rather than the skin.
The biopsy needle goes in next. It’s a larger, hollow needle that cores out a tiny cylinder of bone and marrow, typically just a centimeter or two long. You’ll feel pressure and possibly a dull ache. The entire needle portion of the procedure generally takes about 10 minutes, though your total time at the facility will be longer due to prep and a short observation period afterward.
What the Pain Actually Feels Like
This is the question most people really want answered. The numbing injection itself stings, similar to any local anesthetic. Once the area is numb, the needle insertion feels like deep pressure rather than sharp pain. The moment that catches most people off guard is the aspiration, when the liquid marrow is suctioned out. It creates a sudden, intense pulling sensation deep in the hip that lasts only a few seconds. Patients describe it as unlike anything they’ve felt before, but it’s brief. The biopsy portion that follows tends to feel like firm pressure and twisting.
Pain tolerance varies widely. Some people find it manageable with local anesthesia alone. Others prefer sedation, especially if they’ve had a previous biopsy and know what to expect. If sedation is an option at your facility, it’s worth discussing ahead of time.
Recovery and Aftercare
A small bandage is placed over the site after the needles are removed, and you’ll be asked to lie on your back or apply pressure for 10 to 15 minutes to reduce bleeding. Most people can go home within an hour. Soreness at the biopsy site is normal and typically lasts a few days, sometimes up to a week. Over-the-counter pain relievers and an ice pack usually manage it well.
You’ll generally be advised to keep the site dry for 24 hours, avoid strenuous activity or heavy lifting for a day or two, and watch for signs of infection like increasing redness, swelling, or fever. Serious complications are rare. A large study of 775 procedures found a complication rate of just 0.3%, with significant bleeding and infection being the primary concerns in that small fraction.
What Your Results Mean
The samples are sent to a pathology lab, where a specialist examines them under a microscope and runs additional tests. Results typically take several days to a couple of weeks, depending on the complexity of the analysis. The pathology report covers several key areas.
Cellularity refers to how much of the marrow space is occupied by blood-forming cells versus fat. In healthy adults, the expected cellularity roughly equals 100 minus your age (so a 40-year-old would have about 60% cellularity). Significant deviations can point to conditions like aplastic anemia (too few cells) or leukemia (too many). Morphology describes how the cells look: their size, shape, and maturity. Abnormal-looking cells can indicate cancer or other marrow disorders.
In many cases, the lab also performs genetic testing on the sample, looking for chromosome abnormalities or specific gene mutations that help identify the exact type of blood disorder and guide treatment choices. For blood cancers, these genetic findings often matter as much as the cell appearance in determining prognosis and which therapies are most likely to work.
Your doctor will review the full report with you and explain what the findings mean for your specific situation, including whether further testing or treatment is needed.