Becoming a stem cell donor starts with joining a registry, which takes about 10 minutes online and a free cheek swab at home. You must be between 18 and 35 years old to join, and you’ll need to meet certain health requirements. From there, you wait until you’re potentially matched with a patient who needs a transplant. That match could come in months, years, or never, but staying on the registry keeps you available for someone whose life may depend on it.
Who Can Join the Registry
The age window is 18 to 35. Minors can’t join because donation is a medical procedure requiring informed consent, and people over 35 aren’t eligible to register (though existing members can remain on the registry past that age). Beyond age, a number of health conditions will disqualify you. These include HIV, heart disease (including prior heart attacks, bypass surgery, or pacemakers), autoimmune disorders like multiple sclerosis or lupus, serious liver diseases like hepatitis B or C, and a history of stroke or significant brain injury.
Chronic conditions that affect daily function can also rule you out: asthma requiring daily oral steroids, severe arthritis (rheumatoid, psoriatic, or advanced forms), chronic back pain needing ongoing treatment, and serious kidney problems like polycystic kidney disease in people over 40. Anyone who has previously received an organ transplant, a stem cell transplant, or a tissue transplant from an animal is also ineligible. If you’re unsure about a specific condition, the screening questions during registration will flag it.
How to Register
The main U.S. registry is run by NMDP, formerly known as Be The Match. The process has three steps:
- Order a free swab kit. You’ll answer a few screening questions online to confirm eligibility, then provide a mailing address. The kit typically arrives in 3 to 7 days.
- Swab your cheeks and mail it back. The kit includes instructions and a prepaid return envelope. Your cheek swab samples are processed to determine your tissue type, which gets added to the registry.
- Stay connected. Keep your phone number, email, and address current. Matching is complex, and some donors are contacted quickly while others wait years. The single most helpful thing you can do for patients is remain reachable and committed.
How Matching Works
Stem cell matching isn’t based on blood type. It relies on a set of proteins on the surface of your cells called HLA markers. These markers are inherited, which is why a patient’s best chance of a perfect match is usually a sibling. When no family match exists, doctors search the registry for an unrelated donor whose HLA markers closely align.
The likelihood of finding a match varies significantly by ethnicity. About 90% of white, non-Hispanic patients find a suitable match through the registry. For Hispanic patients, that number drops to roughly 76%. For Black or African American patients, it’s around 62%. This gap exists for two reasons: greater genetic diversity within these populations makes precise matches harder to find, and these groups are underrepresented on donor registries. If you belong to an underrepresented group, your registration carries extra weight.
What Happens If You’re Matched
Being matched doesn’t mean you donate immediately. You’ll go through additional blood tests to confirm compatibility, a physical exam, and a detailed informed consent process. You then donate through one of two methods, and the patient’s doctor determines which one is needed.
Peripheral Blood Stem Cell Donation
This is the more common method. For four or five days before donation, you receive daily injections of a medication that pushes stem cells out of your bone marrow and into your bloodstream. The most common side effects of these injections are bone and joint pain, headaches, fatigue, and general achiness, similar to how you might feel with the flu. Some donors also experience nausea, trouble sleeping, or soreness at the injection site.
On donation day, blood is drawn from one arm, passed through a machine that filters out the stem cells, and returned through your other arm. The process typically takes several hours, and you may need to return for a second session the following day.
Bone Marrow Donation
This is a surgical procedure done under anesthesia. Needles are inserted through the skin into the back of the pelvic bone to withdraw liquid marrow. The procedure takes one to two hours. Afterward, you’re monitored in a recovery room and occasionally kept overnight. Expect tiredness, weakness, and mild back or hip pain in the days following. Most donors return to their normal routine within a couple of days, though full recovery can take up to two weeks. Over-the-counter pain relievers like acetaminophen or ibuprofen are typically enough to manage discomfort.
Costs and Financial Support
You won’t pay for any medical costs related to your donation. The patient’s insurance or the registry covers all medical exams, the procedure itself, and follow-up care. Federal programs also exist to reimburse donors for travel, lodging, and meals associated with evaluation, the donation procedure, and medical follow-up for up to two years afterward. If your employer doesn’t offer paid leave for donation, some registries can help navigate that as well.
Long-Term Safety
A large prospective study tracked over 21,600 donors, including more than 14,500 who donated through the blood-draw method and over 7,100 who donated bone marrow. Researchers found no increased risk of blood cancers, other cancers, autoimmune diseases, or blood clotting events in either group. The rates of these conditions among donors matched what you’d expect in the general population. Both donation methods have strong long-term safety profiles.
Contacting Your Recipient
Donation is anonymous at first. During the first year after transplant, most registries allow donors and recipients to exchange anonymous letters, cards, or emails without sharing identifying details. In the U.S., direct contact (sharing names, meeting in person) requires a one-year waiting period after transplant, and both parties must consent. If your recipient lives in another country, the waiting period may be longer, and some countries prohibit direct contact entirely. If the transplant used cord blood rather than an adult donor’s cells, no contact is possible at all.