Bone marrow is taken using a needle inserted through the bone into the soft, spongy marrow inside. The procedure is done at the back of the hip bone in most cases, takes about 15 to 30 minutes, and involves either withdrawing liquid marrow, a small cylinder of solid marrow tissue, or both.
Two Types of Samples
There are two distinct procedures, and they’re often performed together in a single visit. In a bone marrow aspiration, a hollow needle is inserted through the bone and a syringe is used to pull out a small amount of the liquid portion of marrow, roughly 0.3 to 0.5 milliliters. That’s less than a tenth of a teaspoon. Taking more than that risks diluting the sample with regular blood, which makes it harder to analyze.
In a bone marrow biopsy, a larger needle is used to extract a small cylinder of solid marrow tissue. This core sample needs to be at least 2 centimeters long (about the width of a nickel) to give the lab enough material to work with. Together, the liquid and solid samples show whether your marrow is producing normal blood cells and can help diagnose blood cancers, infections, and other marrow disorders.
Where the Sample Is Taken
The back of the hip bone, called the posterior iliac crest, is the standard site. It’s the bony ridge you can feel at the top of your pelvis toward your lower back. This spot is preferred because the bone is close to the surface, the marrow space is large, and it’s far from vital organs. In some cases, particularly for aspiration only, the breastbone can be used instead.
You’ll typically lie on your side or stomach with the hip area exposed while everything else is draped off.
How the Area Is Numbed
The skin, the tissue underneath, and the surface of the bone itself are all numbed with a local anesthetic, most commonly lidocaine. This is done in layers: first a small injection just under the skin to create a numb patch, then a deeper injection down to the bone’s surface (the periosteum). Before proceeding, the doctor tests whether the numbing worked by gently pressing the bone with the needle tip and asking if you feel any sharp pain.
Some patients also receive light sedation through an IV, typically a calming medication that reduces both pain and anxiety. For children or patients who need deeper sedation, a combination of sedation drugs or inhaled pain-relieving gas (a mix of nitrous oxide and oxygen) can be used. The gas can be self-administered by breathing through a handheld device before and during the procedure.
Step by Step: The Aspiration
Once the area is numb, a small cut is made in the skin with a blade. A special aspiration needle with an inner rod (called a stylet) is pushed through the incision and pressed against the bone. The doctor advances the needle by slowly rotating it clockwise and counterclockwise, drilling through the hard outer layer of bone.
When the needle breaks through into the softer marrow cavity, there’s a noticeable drop in resistance. At that point, the inner rod is removed and a syringe is attached. The actual aspiration, the moment the marrow is pulled into the syringe, lasts only a few seconds. This is the part most people describe as the most uncomfortable: a brief, deep pulling or cramping sensation in the hip. It’s sharp but short-lived, and it’s caused by the suction drawing marrow out of the bone, which the local anesthetic can’t fully block.
Step by Step: The Biopsy
If a solid tissue sample is also needed, it’s usually taken right after the aspiration through the same skin incision or a nearby spot. A slightly larger, specially designed needle is inserted through the bone the same way. Once inside the marrow cavity, the needle is advanced and rotated to cut and capture a small cylinder of solid marrow. The needle is then withdrawn with the core sample inside it.
This part can produce a feeling of pressure or deep aching in the hip. Like the aspiration, the most intense sensation typically lasts only seconds.
What It Feels Like
The numbing injections sting, similar to any local anesthetic. Once the area is numb, you’ll feel pressure as the needle is pushed into bone, but it shouldn’t be sharp. The aspiration pull is the sensation people remember most: a sudden, deep ache or tugging feeling that fades quickly. The biopsy portion involves similar pressure. Overall, most people rate the discomfort as moderate and brief rather than severe.
If you’ve been given IV sedation, you may feel drowsy or slightly out of it during the procedure and may not remember much of it afterward.
Recovery and Aftercare
After the needle is removed, pressure is applied to the site for several minutes to stop bleeding, and a bandage is placed over the area. You’ll need to keep the bandage on and dry for 24 hours. No showers, baths, or swimming during that time.
If you received sedation, you may feel lightheaded afterward. You shouldn’t try to stand or walk until the numbness and dizziness fully pass. Soreness at the site is normal and can last a few days. Bruising is common and will look black and blue before fading on its own over the following week or so. Most people return to normal activities within a day or two, though the site may feel tender when you press on it or lie on that side for a bit longer.
Risks
Bone marrow procedures are considered very safe. Serious complications like significant bleeding or infection are rare. The most common aftereffects are soreness and bruising at the site, both of which resolve without treatment. People taking blood-thinning medications may have a slightly higher risk of bleeding and should let their doctor know beforehand.