Most healthy adults between 18 and 60 can be stem cell donors, though registries actively recruit people ages 18 to 35 because younger donors produce better outcomes for patients. Beyond age, eligibility depends on your overall health, medical history, and whether your tissue type matches a patient in need. Here’s what determines whether you qualify.
Age and General Health Requirements
You can join a donor registry like the National Marrow Donor Program (NMDP) at age 18. Medical research consistently shows that cells from younger donors give patients the greatest chance of transplant success, so doctors prefer donors in the 18 to 35 range. You’ll remain on the registry past 35, but recruitment efforts focus on that younger window for a reason: younger stem cells engraft more reliably and carry fewer complications for recipients.
Beyond age, donors need to be in generally good health. You don’t need to be an athlete, but you should be free of serious chronic conditions and able to tolerate either a minor surgical procedure or a blood-filtering process without unusual risk.
Conditions That Disqualify You
A number of medical conditions permanently prevent donation. The overarching concern is protecting both the donor’s safety and the recipient’s health, since donated cells become part of the patient’s immune system. The major disqualifiers include:
- HIV
- Cancer, or cancer treatment (chemotherapy or radiation) within the past five years
- Heart disease, including a prior heart attack, bypass surgery, angioplasty, valve replacement, or a pacemaker
- Hepatitis B or C and other serious liver diseases
- Autoimmune conditions that affect the whole body, such as multiple sclerosis, lupus, chronic fatigue syndrome, or fibromyalgia
- Severe arthritis, including rheumatoid, reactive, or psoriatic arthritis
- Kidney disease, such as polycystic kidney disease (if over 40) or chronic glomerulonephritis at any age
- Bleeding disorders like hemophilia or a history of deep vein thrombosis
- Stroke or significant brain injury, even if you’ve fully recovered
- Insulin-dependent diabetes
- Chronic Lyme disease
- Chronic back or hip pain that requires ongoing treatment like daily medication, physical therapy, or chiropractic care
If your condition isn’t on this list, it doesn’t automatically mean you’re cleared. The transplant team reviews your full medical history before approving you as a donor, and some conditions fall into a gray area that gets evaluated case by case.
How Matching Works
Being healthy isn’t enough on its own. You also need to be a tissue-type match for a specific patient. This matching is based on a set of proteins on the surface of your cells called HLA markers. Transplant teams test four key HLA genes, and because each gene has two copies, the ideal match lines up at all eight points: an 8/8 match. When a perfect match isn’t available, a 7/8 match (one mismatched point) is sometimes acceptable, though it carries higher risk.
Your best odds of matching someone are within your own family. Each biological sibling has roughly a 25% chance of being a full match, though actual rates vary by family size. In countries with larger families, the chance of finding a matched sibling climbs significantly. In Canada, where families tend to be smaller, the probability of a sibling match has dropped to under 25% in recent years. When no family match exists, patients turn to the global registry of volunteer donors.
Why Ethnicity Matters for Matching
HLA types are inherited, so they track closely with ancestry. This creates a stark disparity in the registry. White patients have about a 95% chance of finding a race-matched donor. For ethnic minorities collectively, that number drops to around 33%. The gap exists because the registry has historically had far fewer donors of African American, Hispanic, Asian, Native American, and multiracial backgrounds. If you belong to an underrepresented group, joining the registry has an outsized impact because you may be the only potential match for a patient who shares your genetic heritage.
What Donation Actually Involves
There are two ways to donate, and the transplant team chooses the method based on what the patient needs. About 80% of donations today use the blood-draw method rather than surgery.
Peripheral Blood Stem Cell Donation
This is the more common approach. For several days before donation, you receive injections of a medication that pushes stem cells out of your bone marrow and into your bloodstream. On donation day, blood is drawn from a vein in one arm, passed through a machine that filters out the stem cells, and returned to you through the other arm. The whole process takes four to six hours, and some donors need a second session.
The injections can cause bone pain, muscle aches, headaches, fatigue, and nausea. During the filtering process, you might feel lightheaded or notice tingling around your mouth or cramping in your hands. These side effects typically fade within a couple of days after the injections stop.
Bone Marrow Donation
This is a surgical procedure done under general anesthesia. While you’re unconscious, doctors use a needle to withdraw liquid marrow from the back of your pelvic bone (not the spine). The procedure takes one to two hours. Most donors go home the same day, though some hospitals plan an overnight stay.
You can expect soreness at the collection site for several days. Most people return to work or school within two to seven days, and the median time to feel completely back to normal is about 20 days. Your body replaces the donated marrow on its own within a few weeks.
Infectious Disease Screening Before Donation
Even after you’re confirmed as a match, you’ll go through a round of lab testing before the actual donation. Federal regulations require screening for HIV, hepatitis B, hepatitis C, syphilis, and two viruses called HTLV-1 and HTLV-2 that can affect white blood cells. Donors are also screened for cytomegalovirus (a common virus that can be dangerous for immunocompromised patients) and West Nile virus. These tests protect the recipient, who will be in an extremely vulnerable state when they receive your cells.
How to Join a Registry
Joining is simple and free for people in the preferred age range. In the U.S., you can sign up through NMDP (formerly Be The Match) by providing a cheek swab, either at a recruitment event or through a kit mailed to your home. The swab is used to determine your HLA type, which gets added to the global database. You may never be called, or you could be contacted years later if a patient matches your profile. If that happens, you’ll go through a health screening, additional blood tests, and a detailed consent process before anything moves forward.
Joining the registry is a commitment, not just a gesture. If a patient is matched to you and begins the intensive chemotherapy that destroys their existing immune system, they are completely dependent on receiving your cells to survive. Backing out at that stage can be fatal for the patient. The time to weigh the decision is before you sign up, not after a match is found.