Bone marrow is collected using a hollow needle inserted into a large bone, most often the back of the hip. The exact process depends on why the marrow is being collected: a small sample for diagnostic testing, a larger harvest from a donor for transplant, or stem cells filtered from the bloodstream as an alternative to surgical extraction. Each method uses a different approach, but all start with the same basic principle of accessing the spongy tissue inside your bones where blood cells are made.
Where Bone Marrow Is Collected From
In adults, nearly all bone marrow samples come from the posterior iliac crest, the bony ridge at the top back of your hip. This spot is preferred because the bone is close to the surface, the marrow cavity is large, and the area is relatively safe to access without risking damage to major organs or nerves. Occasionally the front of the hip is used instead.
In rare cases, marrow can be drawn from the breastbone, though this is limited to fluid samples only, not solid tissue biopsies. In infants younger than about 12 to 18 months, the lower leg bone is sometimes used because it still contains enough active marrow at that age.
Bone Marrow Biopsy: The Diagnostic Procedure
A bone marrow biopsy is ordered when doctors need to understand what’s happening inside your blood-producing system. It helps diagnose blood cancers like leukemia and lymphoma, unexplained anemia, infections that have spread to the marrow, and other conditions where standard blood tests aren’t giving enough information.
The procedure itself typically takes about 30 minutes. You lie on your side or stomach, and the skin over your hip is cleaned and numbed with a local anesthetic like lidocaine. A special hollow needle is then pushed through the outer layer of bone into the marrow space. Two samples are usually taken: a liquid aspirate (marrow fluid drawn into a syringe) and a core biopsy (a tiny cylinder of solid marrow tissue). Most people feel a brief, deep pressure or aching sensation when the marrow fluid is pulled out, even with the numbing agent in place, because the inside of the bone can’t be fully anesthetized.
Several levels of sedation are available depending on the situation and your anxiety level. Local anesthesia alone handles pain at the skin but won’t make you drowsy. Minimal sedation keeps you awake but more relaxed. Conscious sedation makes you very drowsy, and you may not remember the procedure afterward. Full general anesthesia is rarely needed for a standard biopsy. Some providers also prescribe anti-anxiety medication beforehand, and simple strategies like distraction techniques or having a caregiver present for comfort can help.
Complication rates are very low. A large study of 775 procedures found an overall complication rate of just 0.3%. The most common issues are minor bleeding or soreness at the needle site. After the procedure, you’ll have a small bandage over the area and can typically return to normal activities within a day or two, though the site may feel tender for a few days longer.
Donating Bone Marrow for Transplant
Donating marrow for a patient who needs a transplant is a more involved process than a diagnostic biopsy. It’s a surgical procedure done under general anesthesia in a hospital. Doctors use large hollow needles to draw marrow from both sides of the donor’s pelvic bones, collecting enough to supply the recipient with healthy stem cells. The donor’s body naturally replenishes the donated marrow within a few weeks.
Because it’s a surgery, it carries risks that a simple biopsy doesn’t: reactions to anesthesia, infection, nerve or muscle damage, and soreness or injury at the hip where the needles were inserted. These complications are uncommon, and donors are carefully screened beforehand. Most donors experience hip soreness and fatigue for one to two weeks after the procedure. The collected marrow is processed in a laboratory before being infused into the recipient.
Joining a Donor Registry
If you’re interested in becoming a potential bone marrow donor, you can join the National Marrow Donor Program registry online. The process starts with a simple cheek swab to determine your tissue type, which is then entered into a database and compared against patients who need a match.
The registry focuses recruitment on people ages 18 to 35, because medical research shows younger donors provide the best outcomes for patients and the greatest chance of transplant success. Doctors actively prefer donors in this age range. You need to be in generally good health and willing to donate to any patient in need. Conditions like heart disease, diabetes, or hepatitis can disqualify you or require updating your registry status. Being on the registry doesn’t guarantee you’ll ever be called. If a match is found, you’ll go through additional testing and medical evaluation before any donation happens.
Peripheral Blood Stem Cell Donation: The Alternative
Not all “bone marrow donations” actually involve a needle in your hip. The majority of stem cell donations today use a method called peripheral blood stem cell (PBSC) collection, which skips surgery entirely.
For five days before the donation, you receive daily injections of a medication called filgrastim, which ramps up stem cell production and pushes those cells out of the marrow and into your circulating blood. On donation day, blood is drawn from one arm, passed through a machine that filters out the stem cells, and returned to your body through the other arm. This process, called apheresis, is similar to donating plasma or platelets. Most PBSC donations take 4 to 8 hours and are completed in a single session, though some require a second day.
The entire process from start to finish, including pre-donation appointments, injections, and the collection itself, averages 20 to 30 hours spread across 4 to 6 weeks (not counting travel). Common side effects from the filgrastim injections include bone pain, headaches, and fatigue, which resolve after you stop the medication. The donor’s medical team, not the donor, determines whether surgical marrow harvest or PBSC collection is the better option for the patient’s needs.