Diana, who received a stem cell transplant, with and her family

Donating your stem cells to a relative

If someone in your family needs a stem cell transplant, you might be able to donate your own stem cells to them. Your relative's medical team may have already asked if you want to donate, or you might be just doing some research.

What’s on this page?

We'll tell you more here about the process of donating stem cells to a family member.

Our Donating stem cells to your relative booklet also has more information on what to expect if you decide to donate.


You should never feel pressured to donate your stem cells, even to a family member. It can feel like a big deal and quite overwhelming so, even if you fully understand the process, you may not want to donate and that is totally OK. Your body is yours alone and this is your decision, no matter how unwell your relative is or how much you love them.

How likely am I to be a match?

You and your relative will be tested for a match based on your human leukocyte antigen (HLA) tissue type. Your HLA is what makes you ‘you’ — it’s a key part of your individual genetic make-up.

HLA types are similar to blood groups but much more diverse. To be a suitable donor, you need to have a tissue type that matches your relative — but matching your blood groups isn’t necessary.

Your HLA type is made up of many genes, but when it comes to matching, we are most interested in six of them. Each one of these has two different versions (called alleles) making 12 in total. You inherit one version from your mother and one from your father. When it comes to matching you with a donor, if 11 of these genes match up it’s called an 11/12 match. If all 12 match then you’ve got yourself a 12/12 match. It’s important that your doctors find the best possible match because this will give your body the best possible chance of accepting your donor’s stem cells.

You can read more about HLA matching on our Finding a donor for your stem cell transplant webpage.

Sibling transplant

If you're the sibling of someone who needs a stem cell transplant, you have a 25% chance of being a match.

You will normally be tested first because a fully matched sibling donor is often the preferred option. Siblings are the people most likely to be a perfect match for their brother or sister because they share the same parents.

Speaking to other people, I recognise how lucky I am. If it wasn’t for George, I would have desperately needed a stranger’s help. It could have been a completely different story.

Will, who received stem cells from his brother to treat acute lymphoblastic leukaemia (ALL)

Haploidentical transplant

In certain situations, your relative’s transplant team may consider using stem cells from a family member that’s a half match. This is called a haploidentical transplant. Siblings have a 50% chance of being a half match, while parents are always a half match for their children, and vice versa. This gives a much better chance of finding a suitable donor.

Read more about the different types of stem cell transplant

Anthony Nolan patient Matt&Family

What happens if I’m a match?

You’ll have a chat with your relative’s medical team before you decide to go ahead with testing. They’ll discuss with you:

  • how they will test to see if you are a match
  • what donating will involve
  • the potential impact donating will have on you.

If you're happy to go ahead, someone in the medical team will take some blood from your arm or swab the inside of your cheek. The sample will then be sent to the laboratory for testing.

If the blood or swab test shows you’re a suitable match and you’re happy to proceed, the medical team will arrange a ‘donor assessment’ and medical screen for you. This is to make sure you’re fit and healthy enough to donate.

Please ask as many questions as you want during this appointment. This meeting is for you and it’s really important that you fully understand what’s involved so you can make an informed decision about donating. It’s also vital that you feel as confident and comfortable about your decision as possible.

What would stop me being able to donate?

There are some conditions and medical complications that would rule out donation. These include a medical history of cancer, stroke, heart attack and major heart surgery.  

You may not be able to donate if you...

  • weigh less than 50kg or have a body mass index (BMI) of over 40
  • have severe lung disease, such as asthma, emphysema or lung fibrosis
  • have uncontrolled high blood pressure or other heart complications
  • have an autoimmune condition
  • have epilepsy or other neurological conditions
  • are at risk of contracting hepatitis C, HIV, malaria or other infections
  • have anaemia, sickle cell disease or thalassaemia
  • have recently given birth

There are also some conditions and medical complications that would prevent you from ever being able to donate. These include a medical history of cancer, stroke, heart attack and major heart surgery. Your relative’s medical team will discuss all these with you and they’ll be happy to answer any questions you may have.

When I was with my sister in hospital, it felt hard to ask questions. I wanted to know whether I’d need time off work or if there’d be any long-term after-effects. The staff were very friendly and supportive and I got the information I needed.


How do I donate my cells?

There are two ways you can donate your stem cells:

  • 90% of people donate via their bloodstream in a process called peripheral blood stem cell (PBSC) collection. You’ll receive a course of injections for a few days before, and then go into hospital for the day where stem cells are collected from your bloodstream over 4-5 hours and filtered out using a special machine.
  • 10% of people donate through their bone marrow. The cells are collected from your hip bone while you’re under a general anaesthetic so you won’t feel a thing. You’ll stay in hospital for two nights.

Your relative’s medical team will decide which type of donation will be best for your situation. They will talk you through each type of donation in more detail at your donor assessment appointment.

Read more about the donation process.

Will I need to donate again?

You may have to donate more cells to your relative at some point, as they may need something called a donor lymphocyte infusion (DLI) — a ‘boost’ of cells to make sure the transplant is working as well as possible. A DLI could also be an option if their original condition has come back.

I can’t put into words how lucky I feel to have been able to donate to my brother. Seeing him get better, and knowing I was able to play a part in his recovery, is the best thing I could have asked for.

Harriet, who donated stem cells to her brother Jake

What if I'm not a match? 

You might feel disappointed and worried if you're not a match. Remember that this isn't your fault, it's simply the luck of genetics. There's nothing you could have done.

If there are no other options within your family, your relative's medical team will likely get in touch with us at Anthony Nolan to begin the search for an unrelated donor. This person may come from our register, the UK registry, or wider global registry. Or, there might be a match within our cord bank.

Be kind to yourself

It can be tough to find out that you’re unable to donate for your relative, especially if finding a matching donor is tricky. It can also be a tough and brave decision to not donate if it’s not right for you, or to find out that your relative’s transplant has failed after you have donated.

In all cases, please try to not feel guilty. The transplant process is not easy and lots of factors can affect the journey and outcome. So it’s important to take a step back and look after yourself.

I wasn’t prepared for my sister’s transplant not working the first time. When you donate to a stranger, you can feel good but walk away. When it’s your family member, it’s much more personal and harder emotionally. There’s more worry. My advice is to prepare yourself mentally and physically.

Mark, who donated stem cells to his sister in 2019 and 2022

Be a champion for Anthony Nolan  

If you aren't a match for your relative, you may be for someone else. You can join the Anthony Nolan stem cell register when the time is right. If you’ve been tissue-typed for your sibling and would like to join the Anthony Nolan register, please contact donor.support@anthonynolan.org

If you’re unable to join the register but you’d still like to help, you can support Anthony Nolan in many other ways. You can volunteer on our behalf, take part in a fundraising event (from a bake sale to a marathon), support our campaigns, or simply make a much-needed financial donation to ensure our lifesaving work can continue in the future.

Information published: 10/01/23

Next review due: 10/01/26