What are donor stem cell (allogeneic) transplants?

A donor stem cell transplant is a treatment for cancers and conditions that affect the blood cells. This treatment replaces bone marrow that is no longer working properly with healthy stem cells from another person (your donor). It is also known as an allogeneic stem cell transplant.

The donor stem cells make new red blood cells, white blood cells and platelets. This gives you a new, healthy bone marrow. The transplant also gives you your donor’s immune system (white blood cells). This helps your body to get rid of any remaining cancer cells.

Your donor may be a family member or an unrelated donor. Some people may be given stem cells from an umbilical cord.

Donor stem cell transplants are only done in hospitals with specialised transplant units. Some people may need to travel quite far to their nearest unit. You will usually need to stay in hospital for several weeks.

When is a donor stem cell transplant used

A donor stem cell transplant may be used to treat different blood cancers, such as leukaemia, lymphoma and myeloma. It may also be used to treat some other blood conditions.

Deciding to have a donor stem cell transplant

A donor stem cell transplant may increase the chance of being cured, or of getting you into remission more than any other treatment. But it is a very specialised treatment. It can have many side effects and possible complications.

You need to think about the benefits and risks of this treatment before you decide. Your specialist will talk to you about these. Although this can be upsetting, it is important that they tell you about all the possible risks.

You will need some time to think things over before you make your decision. You may want to talk to your family, friends and partner, if you have one. Most transplant units have a nurse specialist, transplant co-ordinator, social worker or counsellor who you can talk to.

It can help to have someone with you when you talk to the hospital team. They can support you and help you understand the information you have been given.

We have more information on making treatment decisions that might help. This includes information about getting a second opinion and giving permission (consent) for the hospital staff to give you the treatment. 

We have information below about some things you might want to think about. 

Risks of a donor stem cell transplant

There have been lots of developments in the care of people having a transplant. But some people will still have serious side effects or complications that may be life threatening.

Your doctor will consider your general health before advising you to have a transplant. They will also explain the side effects and possible complications of a transplant before you start treatment.

There are likely to be times when you feel very unwell. It can take many months, and sometimes up to a couple of years, to fully recover. Some people may not get back to the same level of health they had before their transplant.

The main risks include:


Having a donor stem cell transplant usually affects whether you can get pregnant or make someone pregnant. This is a side effect of high doses of chemotherapy and sometimes radiotherapy. But it will depend on the treatment you have. Your cancer doctor or transplant nurse will explain the risks in your situation.

Research trials

You may be invited to take part in a research trials. Trials and studies are the only reliable way to find out whether a different type of treatment is better than what is already available.

Stages of a donor stem cell transplant

Stage 1: Preparing for a donor stem cell transplant

Your cancer doctor, nurse or transplant co-ordinator will explain why you are being offered this treatment. They explain the benefits and risks of having a transplant. If you decide to go ahead, your doctors start looking for a suitable donor. You have tests to check your general health, and are given advice on preparing for the treatment. Possible donors are asked to give a blood sample to check that their cells match yours.

Stage 2: Having conditioning treatment

Before the transplant, you have conditioning treatment. This is given to

  • get your body ready to accept the donor stem cells
  • weaken your immune system to reduce the risk of it attacking the donor stem cells
  • remove any remaining cancer cells from your body.

Your conditioning treatment usually takes around 1 to 2 weeks. Your doctor will talk to you about the type of conditioning treatment that is best for you. It usually involves having chemotherapy. Some people also have radiotherapy to the whole body, called total body irradiation (TBI). You may also have antibody therapy.

During conditioning treatment, your doctors may talk about days as numbers. The day of your transplant (stem cell infusion) is Day 0. The days before transplant are counted as Day -8, Day -7, and so on. The days after transplant are counted as Day +1, Day +2, and so on.

You usually finish conditioning treatment 24 to 48 hours before the transplant (Day -2 or Day -1).

You may have your conditioning as an inpatient in hospital. Some hospitals may give some of the conditioning treatment while you are still at home or staying in accommodation nearby. Your doctor or nurse will explain where you will have your treatment.

Types of conditioning

There are different types of conditioning treatment. Your conditioning treatment depends on a few factors:

  • the type of cancer you have
  • your age and general health
  • the type of donor you have and if cord blood is being used
  • what chemotherapy or radiotherapy you had in the past.
  • Full-intensity conditioning (myeloablative)

    You have high-doses of chemotherapy, sometimes with total body irradiation. This is done to destroy your bone marrow and immune system.

  • Reduced-intensity conditioning (RIC)

    This uses fewer or lower doses of chemotherapy or radiotherapy than full-intensity conditioning. It weakens your immune system enough to allow the donor stem cells to grow in your bone marrow. But there is less risk of complications.

    The donor stem cells gradually replace your immune system and attack any remaining cancer cells in your body.

Conditioning with chemotherapy

The nurses give you chemotherapy drugs through your central line or PICC line with plenty of fluids. You usually have treatment over several days. Your nurse will explain about the possible side effects and give you drugs to help control them. They will also give you drugs to help prevent infections and reduce the risk of developing graft-versus-host disease (GVHD).

Conditioning with total body irradiation (TBI)

TBI treats your whole body with radiotherapy. If you need this as part of your conditioning treatment, you usually have TBI twice a day for 6 to 8 sessions. If you are having reduced-intensity conditioning, you may have 1 or 2 low doses.

Possible side effects of TBI include:

  • skin changes
  • tiredness
  • feeling sick
  • diarrhoea
  • loss of appetite
  • dry mouth
  • sore mouth.

These can happen a few days later. The radiographers will explain how to manage the side effects and how to care for your skin.

Conditioning with antibody therapy

You may also be given antibody therapy to help damage (suppress) your immune system. This allows the donor cells to grow and make new blood cells. The drug also reduces the risk of graft-versus-host disease (GVHD).

The most common antibody drugs used for conditioning are:

  • Alemtuzumab (a targeted therapy drug)
  • ATG (antithyroglobulin)

You have the antibody drug as a drip. Some people may have an allergic reaction to it. This is more common after the first dose. The reactions are not usually severe. Your nurse will give you drugs to reduce the risk of a serious reaction and will monitor you closely.

Common symptoms include:

  • an itchy rash
  • a fever and sometimes shivering (rigors)
  • feeling short of breath.

Stage 3: Collecting your donor’s stem cells

While you are having the conditioning treatment, your donor’s stem cells are collected from their blood or bone marrow. The stem cells are collected 1 or 2 days before the transplant. It takes 3 to 4 hours, usually as a day patient.

We have more information about collecting stem cells from a donor.

Stage 4: Having the transplant

You have your transplant of donor stem cells 1 or 2 days after conditioning treatment has finished. The transplant day is known as Day 0.

Your nurse gives you the stem cells as a drip (infusion) through your central line or PICC line. It is like having a blood transfusion.

Some people have mild side effects while the stem cells are being given, such as feeling sick or breathless. Your nurse will give you drugs through your central line before the stem cell infusion. This is to reduce the risk of an allergic reaction. They monitor you carefully during and after the stem cell infusion.

If the stem cells were frozen, you and your visitors might notice a strong smell like sweetcorn. This can last for a few days after the infusion. It is from the preservative used to protect the stem cells during freezing.

Immunosuppressant drugs

Your doctors will give you drugs to suppress your immune system and the new immune system from your donor. These are called immunosuppressant drugs. They help to prevent graft-versus-host disease (GVHD). This is when your cells and the new stem cells react against each other.

Different drugs can be used. You will have either ciclosporin or tacrolimus. They are often given with other drugs such as methotrexate or mycophenolate.

You usually start taking them in the days before your transplant and keep taking them for a few months. It is very important to take them.

Immunosuppressant drugs have side effects. Your doctor or nurse will tell you about these.

Stage 5: Waiting for your new blood cells to grow

The stem cells travel through your blood to your bone marrow. They then begin to make new blood cells. This is called engraftment.

It can take from 10 days to 3 weeks before some of the new blood cells are released into the blood. If you had a cord blood transplant, it can take longer. This means you will have low numbers of red blood cells, white blood cells and platelets in your blood for some time. This can cause side effects, including:

  • infection – because of low white blood cells
  • bleeding – because of low platelets
  • anaemia – low red blood cells.

You will have blood samples taken every day to check your blood count. You may need transfusions of blood or platelets to help. You may also need antibiotics. Your transplant team will care for you and monitor you very closely for complications.

You may be given a drug called G-CSF as an injection. It helps your bone marrow to make new blood cells. This reduces the length of time you are at risk of side effects.

Stage 6: Recovering after your transplant

When your blood cells have recovered, and you are well enough, you can go home. Your doctor or nurse will tell you what you should do to reduce the risk of getting an infection. You will have regular appointments at the day unit or outpatient clinic to check recovery. It may take months to recover from a transplant.

Going into hospital

If you are having your conditioning treatment in hospital, you will go in 1 to 2 weeks before the transplant. Or you may go in during, or after, the conditioning treatment. You may be in a room of your own, but it depends on the unit you are in.

The nurses will suggest what to take to keep you busy and make you more comfortable. Most hospitals have TVs, but you may also want to take a tablet or laptop, books, magazines or games, or personal things, like photos.

Take some comfortable, loose-fitting clothes. Soft, cotton materials are best. Tops with buttons make it easier when you are being examined. An eye mask and ear plugs may help you sleep better.

Ask the nurses for advice about the toiletries you should bring.


Visitors, especially close family, friends and your partner, if you have one, are important. They give you support and help you stay in touch with life outside hospital. Some units have rooms for family members to stay overnight if they have far to travel.

Most units are flexible about visiting, but different hospitals have different rules. You may be restricted to a certain number of visitors each day. This is to help protect you from infection. Any visitor who has, or thinks they have, an infection should not visit you. The nurses will explain more about this to you.

Side effects of donor stem cell transplants

The side effects will depend on several things, including the type of conditioning treatment you had and your general health. People having a reduced-intensity transplant may have less severe side effects. Your hospital team will give you more information about what to expect.

We have more information about the possible side effects of donor stem cell transplants.

After a donor stem cell transplant

Going home

When your blood counts have reached a safe level, your transplant team will talk to you about going home.

You may feel impatient to go home but anxious about leaving the support of the hospital. If you live on your own, you need to arrange for a relative, friend or partner to stay with you. Or the hospital staff can arrange support from carers when you go home.

It can take time to adjust after spending so long in hospital. As you recover, you will find that things gradually shift away from the treatment and back to day-to-day living.

When to contact the hospital

Always carry the 24-hour hospital phone number you have been given. If you are worried about anything, call the number at any time of day or night. The doctors and nurses on the transplant unit always prefer you speak to them rather than risk being unwell at home.

Contact your hospital straight away on the number you have been given if:

  • your temperature goes over 37.5°C (99.5°F)
  • you suddenly feel unwell, even with a normal temperature
  • you have any signs of an infection – such as feeling shivery or short of breath, having a sore throat or cough, having diarrhoea or needing to pass urine often
  • you have any symptoms of GVHD
  • you cannot take your tablets
  • you have a rash on your skin, or any signs of bleeding
  • you have been in contact with someone who has an infectious disease, for example chickenpox or measles.

If you feel unwell and are unable to contact the hospital, ask someone to take you to the nearest hospital accident and emergency (A&E) straight away. You may need to be admitted to hospital. It is quite common for this to happen once or twice. Although this can be worrying for you, it is not a major setback.

The first few months out of hospital

For the first few months, you will have a clinic appointment every week. To begin with, it may sometimes be twice a week. There you will see your specialist doctor and have blood tests.

You may still need blood or platelet transfusions. You are still at risk of infection, because your immune system is weak. You usually need to take drugs, such as antibiotics, anti-viral and anti-fungal drugs. These reduce your risk of infection. You will also continue taking the drugs to reduce the risk of graft-versus-host disease (GVHD). Always take your medicines as they have been explained to you.

You will need to take some precautions and be careful with hygiene as you recover. Your transplant team will explain this to you and tell you how to recognise the signs of infection.

Your team will also check how the treatment has worked. You may have: 

  • tests to check that there are no signs of cancer

    This may be with scans or a bone marrow biopsy. How they check will depend on the type of cancer you have.

  • tests to check how well your donor's cells have engrafted (chimerism)

    Chimerism is a word doctors use to describe how well your donor’s cells have engrafted. After transplant, the aim is for full donor chimerism. This is when all your blood and bone marrow are from your donor. Sometimes chimerism is given as a percentage. It should be as near to 100% as possible.

    Mixed chimerism means some of your own cells are still there. This is more likely if you had reduced-intensity conditioning. Because you had lower doses of chemotherapy, some of your own blood cells survive.

    Sometimes mixed chimerism gradually improves on its own. If it does not get better, doctors can treat it by

    • changing the dose of your immunosuppressant drugs.
    • giving you white blood cells from your donor as a drip into your line (a donor lymphocyte infusion or DLI). The donor white blood cells destroy any of your remaining cells. The aim is to increase the chimerism level to full donor chimerism. The main risk of a donor lymphocyte infusion is that you might develop graft-versus-host disease (GVHD). Your doctor will talk to you about any risks.

Your feelings during treatment

Having a stem cell transplant is probably one of the most stressful things you will ever face. It is emotionally hard, as well as physically demanding.

There may be times when you are anxious, frightened or depressed. You may ask yourself questions like:

  • ‘Is the treatment working?’
  • ‘Will my blood counts ever go up?’
  • ‘How am I going to cope with the side effects?’.

Talking to family and friends about how you are feeling often helps. The nurses and doctors can also give you advice and support. They may be able to put you in contact with someone else who has had a stem cell transplant. Many people find this very useful.

If you are finding it difficult to cope, tell your nurse or doctor. You may find it helpful to talk to someone such as a counsellor. The hospital staff can arrange this for you.

Support from Macmillan

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About our information

  • References

    Below is a sample of the sources used in our stem cell and bone marrow transplants information. If you would like more information about the sources we use, please contact us at cancerinformationteam@macmillan.org.uk

    Carreras, Dunfour, Mohty and Kröger. The European Society for Blood and Bone Marrow Transplantation: Hematopoietic stem cell transplantation and cellular therapies. Springer, Switzerland. 2019. 

    FACT-JACIE International Standards for Hematopoietic Cellular Therapy – product collection, processing and administration. 7th edition. 2018. 

    Anthony Nolan. Operations and patient services user guide. Available from www.anthonynolan.org. Accessed January 2019.

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Dr Anne Parker, Consultant Haematologist.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.

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