Blood Stem Cell Donation: How It Works, Who Can Donate, and What to Expect
Updated: 6 days ago
Written and medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026 · How we review
Quick Answer
Blood stem cell donation is a procedure that collects healthy blood-forming cells from a donor's bloodstream for a person who needs a stem cell (bone marrow) transplant. After 4–5 days of daily filgrastim injections, a machine filters stem cells from the blood over about 4–6 hours a day for 3–4 days. Side effects are usually mild and short-lived. [1]
What the research says
Blood stem cell donation has fewer serious problems than marrow surgery. In a study of 9,494 U.S. donors, serious adverse events occurred in 0.56% of blood stem cell donors compared with 2.38% of bone marrow donors. Cancer, autoimmune disease and blood clots were no more common after donation. (Pulsipher et al., Blood, 2014)
Serious events are rare across tens of thousands of donations. Teams in 35 countries reported on 51,024 donations: severe adverse events occurred in about 7 per 10,000 donations, and blood cancers in donors did not exceed the rate expected in the general population. (Halter et al., Haematologica, 2009)
Ten years of donor follow-up found no deaths. In 1,105 Swiss donors (80% gave blood stem cells), no fatal complications occurred, serious collection-related events stayed near 1%, and cancer and autoimmune disease rates did not exceed general population rates. (Rüesch et al., Bone Marrow Transplantation, 2022)
Key takeaways
Blood stem cell donation is the most common way to donate stem cells.
Joining the registry starts with a health questionnaire and a cheek swab.
Daily injections for 4–5 days come before the collection.
Collection is done through the veins in your arms, not through surgery.
Side effects are usually mild and short-lived.
Donating does not raise your risk of blood problems or cancer.
What is blood stem cell donation?
Blood stem cell donation is the procedure doctors use to collect blood-forming stem cells from a donor's bloodstream for a stem cell transplant. [1]
Blood stem cells are the young cells in your bone marrow that grow into red blood cells, white blood cells and platelets.
Each year, about 18,000 people in the U.S. learn they have a disease, such as a blood cancer, that a stem cell transplant could help treat. [1] [2]
People donate blood stem cells for three reasons:
As part of their own treatment
To help a close family member who needs a transplant
To help a stranger, by joining a donor registry
What are the ways to donate stem cells?
Method | How it works | How common |
Blood stem cell donation | Stem cells are filtered from your blood through the veins in your arms | The most common method |
Bone marrow donation | Stem cells are taken directly from the bone marrow | Less common |
Umbilical cord blood donation | Parents can choose to donate cord blood after a baby is born | Only possible at birth |
Why do people need donated blood stem cells?
People need donated blood stem cells when a blood cancer or blood disorder damages the stem cells in their bone marrow, so a transplant can replace them with healthy donor cells. [1]
The new cells then start making healthy red cells, white cells and platelets.
Stem cell transplants are used to treat many conditions, including:
Leukemia
Multiple myeloma
Myelodysplastic syndrome
Myeloproliferative disorders, such as polycythemia vera
How are blood stem cell donors and patients matched?
Blood stem cell donors and patients are matched by comparing human leukocyte antigens (HLA), markers on your cells that tell your immune system what belongs in your body and what does not. [1]
The more HLA markers match, the better the donated cells can build new, healthy blood cells and a new immune system.
Donor type | Who they are | Match level |
Close family member | A biological parent or sibling | May be a full match |
Unrelated donor | A stranger found through a donor registry | Matched by HLA testing |
Haploidentical donor | A first-degree family member | At least half of the patient's HLA markers match |
Where are unrelated donors found?
Donor registries keep records of people who have agreed to donate. In the U.S., a national registry holds this list. Transplant teams can also search international registries to find a match. [2]
How do you become a blood stem cell donor?
To become a blood stem cell donor, you fill out a health questionnaire, give a cheek swab for HLA typing and join a donor registry; if you match a patient, you then complete a blood test, counseling, a physical exam and further blood tests. Each step protects both you and the patient. [1]
Fill out a health questionnaire. You share your health history and contact details and sign an agreement to join the registry. Some medical conditions rule out donation.
Give a cheek swab. A cotton swab collects cells from inside your cheek for HLA typing. You can do this at a donor center or with a mail-in kit. Your HLA type is added to the registry.
Wait for a match. The registry contacts you if your HLA type closely matches a patient. This can take months or even years.
Give a blood sample. If you are a close match, the transplant team uses it to confirm the match.
Meet a counselor. You review the requirements, procedure and risks, then sign an informed consent form.
Have a physical exam and blood tests. These confirm that you have no condition that would stop you from donating.
Who cannot donate blood stem cells?
People outside the registry's age limit or with certain health conditions, such as HIV/AIDS, hepatitis B or C, heart disease or bleeding disorders, cannot donate blood stem cells. The two main factors are age and health history. [1]
In the U.S., only people aged 18 to 40 can join the national registry as new donors. The limit exists because many people develop health conditions as they get older that would rule them out. Age limits can differ in other countries.
Condition | Why it matters |
HIV/AIDS | Rules out donation |
Severe arthritis, such as rheumatoid arthritis | Rules out donation |
Autoimmune diseases that affect the whole body | Rules out donation |
Bleeding or clotting disorders, such as hemophilia or deep vein thrombosis | Rules out donation |
Brain injury | Rules out donation |
Cancer, or chemotherapy or radiation therapy, or cancer treatment in the past 5 years | May rule out donation |
Chronic hip, back or spine pain treated with medicine | Rules out donation |
Chronic Lyme disease | Rules out donation |
Diabetes that needs insulin | Rules out donation |
Heart disease: past heart attack, angioplasty, bypass surgery, valve replacement or pacemaker | Rules out donation |
Hepatitis B or hepatitis C | Rules out donation |
Kidney disease | Rules out donation |
This list is not complete. If you want to donate but are unsure whether you qualify, ask a doctor to review your health history.
What happens before blood stem cell donation?
Before blood stem cell donation, confirmed donors repeat some health tests about 30 days ahead and then receive one filgrastim injection a day for 4–5 days to move stem cells into the blood. Once you are a confirmed match, the donor center schedules your collection days. [1]
Final health check
About 30 days before donation, you repeat some tests to make sure nothing has changed since you joined the registry. These may include:
Chest X-ray
Electrocardiogram (ECG)
Complete blood count (CBC)
Comprehensive metabolic panel
Infectious disease tests
Pregnancy test for women
Filgrastim injections
If you are healthy enough to donate, you get a medicine called filgrastim. It tells your bone marrow to make more stem cells and release them into your blood.
Most people get one injection a day for 4–5 days before donation.
Possible side effect | What helps |
Bone pain | Over-the-counter acetaminophen or ibuprofen |
Headache | Over-the-counter acetaminophen or ibuprofen |
Mild fever | Over-the-counter acetaminophen or ibuprofen |
Nausea | Ask the donor center team for advice |
Trouble sleeping | Ask the donor center team for advice |
These side effects usually go away soon after the injections stop. Rarely, filgrastim can enlarge or rupture the spleen, so get medical help right away for pain in the upper left belly or the tip of the shoulder.
Eating and drinking
There are no food or drink restrictions. It does help to:
Drink plenty of fluids for a few days before donation
Eat breakfast on the morning of your appointment
What to bring
Ask the donor center whether you need someone to drive you there and back. You may also want a favorite pillow, something to read, or games on your phone or tablet.
What happens during blood stem cell donation?
During blood stem cell donation, a machine collects stem cells from blood drawn through a needle in one arm and returns the rest of the blood through a needle in the other arm. Doctors sometimes call this step "harvesting" the cells. [1]
You sit in a comfortable chair or lie on a bed.
A needle is placed in a vein in each arm.
One needle connects to a thin, flexible tube (catheter) that carries your blood to a machine.
The machine collects the stem cells from your blood.
The tube in your other arm returns the rest of your blood to you.
The stem cells are collected in a bag and stored for the patient.
Each session takes about 4–6 hours, and collecting enough cells usually takes 3–4 days.
Side effects during collection
Side effects are rarely serious. The blood returned to you contains a medicine that stops it from clotting. This medicine can lower your calcium level, which may cause:
Muscle cramps
Lightheadedness
Tingling
Your donor team may give you a calcium supplement to ease these symptoms.
How long does recovery take after blood stem cell donation?
Most people recover from blood stem cell donation as soon as each session ends and can return to work or their normal routine afterward. [1]
You can return to work or your normal routine after each session.
Filgrastim side effects usually fade once the donation process is complete.
Contact the donor center care team if you have any questions or concerns.
What are the risks and benefits of blood stem cell donation?
Blood stem cell donation can give a patient a real chance to overcome a serious illness, while its risks are mostly short-term side effects, and it does not raise the donor's risk of blood problems or cancer. [1] [3]
Benefits | Risks |
You give someone a real chance to overcome a serious illness | Short-term side effects from the daily injections |
The patient may be a sibling, relative, friend or stranger | Cramps, tingling or lightheadedness during collection |
Recovery is fast for most donors | Very few overall risks |
— | Donating does not raise your risk of blood problems or cancer |
Do blood stem cell donors and patients ever meet?
Blood stem cell donors and patients can meet, but only if both agree. The healthcare and transplant organizations that coordinate the donation also arrange these meetings. [1]
Conclusion
Blood stem cell donation asks for a few days of your time, a short course of injections and some long sessions in a comfortable chair. In return, it can give a person with a blood cancer or blood disorder a chance at a healthy life.
Most donors recover right after the last session, and serious problems are rare. If you are thinking about it, the first step is simple: a health questionnaire and a cheek swab.
Ready to take the next step? Talk to your doctor about whether you qualify, then contact a donor registry to join. Want to understand the conditions a transplant can treat? Explore our bone marrow failure guide and keep learning in our health library.
Frequently asked questions
Is donating blood stem cells painful?
The collection itself works like a long blood donation, with a needle in each arm. The daily injections beforehand can cause bone pain, headache or mild fever, which over-the-counter pain relievers usually ease.
How long does blood stem cell donation take?
Each collection session takes about 4–6 hours. Most donors need 3–4 days to collect enough cells, after 4–5 days of daily injections.
What is the age limit for stem cell donation?
In the U.S., people aged 18 to 40 can join the national registry as new donors. Other countries may set different limits.
Is blood stem cell donation the same as bone marrow donation?
No. Blood stem cell donation filters stem cells from your bloodstream through your arm veins. Bone marrow donation takes the cells directly from the bone marrow. Blood stem cell donation is the more common method.
Does donating stem cells increase my risk of cancer?
No. Donating blood stem cells does not increase the risk of a blood disorder or cancer.
Can I eat before donating stem cells?
Yes. There are no food restrictions. Eat breakfast on the day of your appointment and drink plenty of fluids in the days before.
How soon can I go back to work after donating?
Most people return to work or their normal routine after each donation session.
Will I meet the person who receives my stem cells?
Only if both you and the recipient agree. The transplant organizations involved can arrange the meeting.
What are the side effects of filgrastim injections?
The most common side effects are bone or muscle aches, headache and tiredness. They usually go away within a few days after donation.
Can I change my mind after joining the donor registry?
Yes, donating is always voluntary. If you decide not to donate, tell the registry as early as possible, because a patient may be getting ready for transplant.
Related reading
Bone Marrow Donation: Who Can Donate and How It Works explains how bone marrow donation works.
Allogeneic Stem Cell Transplant: Process, Risks and Recovery explains donor stem cell transplants.
Helpful external resources
References
Cleveland Clinic. Blood Stem Cell Donation: What It Is, Process & How It Helps. Cleveland Clinic. Last updated November 17, 2023. https://my.clevelandclinic.org/health/treatments/blood-stem-cell-donation
U.S. Health Resources and Services Administration. About. HRSA Blood Stem Cell. Last reviewed June 2026. https://bloodstemcell.hrsa.gov/about
Pulsipher MA, Chitphakdithai P, Logan BR, et al. Lower risk for serious adverse events and no increased risk for cancer after PBSC vs BM donation. Blood. 2014;123(23):3655-3663. PMID: 24735965. https://doi.org/10.1182/blood-2013-12-542464
Halter J, Kodera Y, Ispizua AU, et al. Severe events in donors after allogeneic hematopoietic stem cell donation. Haematologica. 2009;94(1):94-101. PMID: 19059940. https://doi.org/10.3324/haematol.13668
Rüesch M, Amar El Dusouqui S, Buhrfeind E, et al. Basic characteristics and safety of donation in related and unrelated haematopoietic progenitor cell donors - first 10 years of prospective donor follow-up of Swiss donors. Bone Marrow Transplantation. 2022;57(6):918-924. PMID: 35379914. https://doi.org/10.1038/s41409-022-01656-z
Medical disclaimer
This article is for general education and does not replace advice from your own doctor.
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