Bone marrow is removed in two very different contexts: as a medical procedure to diagnose disease or harvest stem cells, and as a cooking technique to extract rich, fatty marrow from bones for eating. The method depends entirely on which one you’re after. Medical extraction uses specialized needles and takes place in a clinic or operating room, while culinary extraction typically involves roasting bones in a hot oven until the marrow softens.
Removing Bone Marrow for Cooking
If you’re working with beef or veal marrow bones from a butcher, the process is straightforward. Start by soaking the bones in salted ice water in the refrigerator for up to 24 hours. This draws out residual blood and gives you a cleaner-looking result. Replace the water with fresh salted ice water every four to six hours. Soaking isn’t strictly required, but it makes a noticeable difference in appearance and flavor.
When you’re ready to cook, pat the bones dry with a clean towel and preheat your oven to 450°F. Place the bones cut-side up (or fat-side up for canoe-cut bones) on a rimmed baking sheet or in a cast iron skillet. Roast for 15 to 25 minutes, depending on the size of the bones, until the marrow is very hot, soft, and has a jelly-like texture. You’ll know it’s done when the marrow has slightly pulled away from the bone and jiggles when you nudge it. Scoop it out with a small spoon or spread it directly onto toasted bread with a sprinkle of coarse salt.
If you want raw marrow out of the bone (for adding to ground meat or broth), you can push it out of the center of a marrow bone using your thumb or the handle of a wooden spoon after a brief soak in warm water to loosen it slightly.
Medical Bone Marrow Removal: Two Types
In medicine, bone marrow is removed either as a small diagnostic sample (biopsy and aspiration) or in larger quantities for transplant (stem cell harvest). These are fundamentally different procedures with different goals, though both typically draw marrow from the hip bones.
A bone marrow aspiration withdraws liquid marrow through a hollow needle attached to a syringe. A bone marrow biopsy uses a larger, specially designed needle to extract a small cylindrical core of solid marrow tissue. Most of the time, both are done together in a single visit, with the aspiration performed first. The liquid sample lets pathologists examine individual cells under a microscope and run genetic tests, while the solid core shows the overall structure of the marrow, including how densely packed with blood-forming cells it is versus fat.
Where the Sample Comes From
In adults and most children, marrow is taken from the posterior superior iliac crest, the bony ridge at the back of your pelvis that you can feel just above each buttock. This spot is preferred because it contains highly cellular marrow, sits away from vital organs, and isn’t a weight-bearing structure, so recovery is simpler. In very obese patients, the front of the hip bone is used instead because the rear crest can be difficult to reach. For infants younger than 18 months, the inner surface of the shinbone (tibia) is sometimes used for aspiration because it’s more accessible at that age.
What Happens During the Procedure
You’ll lie face down or on your side. The doctor identifies the correct spot on your hip, either by feeling the bony landmarks or using imaging for guidance, and marks the skin. After cleaning and draping the area, they numb the skin and, critically, the surface of the bone itself with a local anesthetic. The bone surface (periosteum) is highly sensitive, so thorough numbing here matters more than anywhere else. Some centers offer deeper sedation for comfort.
A small skin incision is made, and the aspiration needle is advanced through the bone into the marrow cavity. Once inside, the inner rod (stylet) is removed and a syringe is attached. Drawing back on the syringe pulls liquid marrow into it. This is the moment most people describe as a brief, sharp, deep ache, because the suction creates a sensation that local anesthetic can’t fully block. The pull itself lasts only a few seconds. Several syringes may be filled for different lab tests.
For the biopsy, a slightly larger needle is used to cut and capture a small cylinder of solid marrow tissue. The needle is rotated and angled to free the core, then withdrawn. The entire procedure, aspiration and biopsy combined, typically takes about 15 to 30 minutes.
Pain and Complications
Pain is the most common issue. In one study of 274 patients, about 15% reported little to no pain, 30% had moderate pain, and 55% described it as severe. That said, a large English national audit found the overall adverse event rate for the procedure is just 0.07%, making serious complications like significant bleeding or infection rare. Soreness at the biopsy site commonly lasts a few days. You can expect a small bandage over the puncture site, and most people resume normal activities within 24 to 48 hours, avoiding heavy lifting or soaking the area in water during that time.
Bone Marrow Harvest for Transplant
When bone marrow is being collected for a stem cell transplant rather than a diagnostic test, the process is larger in scale. The donor goes to an operating room under general or regional anesthesia. A needle is inserted repeatedly into both posterior hip bones, and sometimes the front of the hips as well, to aspirate marrow in multiple small draws. Up to 1,400 mL of marrow (a little under 3 pints) may be collected in a single session. The marrow regenerates on its own over the following weeks.
There’s also a non-surgical alternative called peripheral blood stem cell collection. Instead of drawing marrow directly from the bones, the donor receives a series of injections over four to five days of a medication that stimulates bone marrow to release stem cells into the bloodstream. On the final day, the donor is connected to a machine that filters stem cells from the blood and returns everything else. This is done through a vein in the arm or, if needed, a temporary catheter. The collection session takes several hours but avoids anesthesia and any needle punctures into bone.
What Happens to the Sample After Removal
Once marrow is extracted, it’s processed immediately. Liquid aspirate is spread onto glass slides (typically at least six), air-dried, and preserved so pathologists can examine cell shapes, count different cell types, and look for abnormal cells. Additional aspirate goes into tubes with preservatives for genetic testing, which can reveal chromosomal abnormalities linked to blood cancers and other marrow disorders. The solid biopsy core is either placed in a fixative solution or gently touched against glass slides to create “touch prep” imprints before being sent to the lab for sectioning and staining. Together, these samples give a complete picture of how the marrow is functioning at both the cellular and structural level.