Why a blood transfusion is done
A blood transfusion can help if you've lost a lot of blood, or if you have certain health conditions that affect your blood or bone marrow.
You may need a blood transfusion if you do not have enough healthy red blood cells. This is called anaemia and it can be caused by:
- losing a lot of blood from an accident, surgery or giving birth
- having a condition that affects the red blood cells or bone marrow, such as sickle cell disease or thalassaemia
- having treatment such as radiotherapy or chemotherapy
You may also need a blood transfusion if you have a condition which means your blood does not clot as well as it should. This can mean you bleed a lot, or for longer than usual.
Depending on your condition, you can be given a transfusion containing:
- red cells – to help with anaemia
- platelets – to help your blood clot
- plasma – to help your blood clot
Sometimes other treatments will be tried before you have a blood transfusion. The doctor will tell you about any alternatives.
What happens when you have a blood transfusion
Blood transfusions take place in hospital.
A doctor or nurse will talk to you about what's going to happen and answer any questions.
You'll have a blood sample taken before starting the blood transfusion, to check the donor blood is the right blood group for you.
You'll usually be asked to sign a consent form. But if a blood transfusion is needed in an emergency, for example during surgery, it might not be possible to get your consent.
How a blood transfusion is given
During a blood transfusion:
- You will sit in a chair or lie on a bed.
- A thin plastic tube is inserted into a vein in your arm.
- The tube is then attached to a bag of blood (called a drip).
- Blood slowly flows into your body from the drip.
- When the transfusion is finished, the drip and tube are removed.
Your pulse, temperature and blood pressure will be checked before, during and after a blood transfusion.
A blood transfusion usually takes up to 4 hours, but it can take longer depending on how much blood you need.
After the procedure
You can usually go home after a blood transfusion unless you are very unwell.
Many people will start feeling better within 24 hours of getting a blood transfusion.
Before you leave hospital, the healthcare team will give you information about possible side effects and complications to look out for.
Side effects of a blood transfusion
Many people have no side effects from having a blood transfusion.
You might have mild symptoms such as:
- a high temperature or feeling hot or shivery – you may be given paracetamol
- a rash on your skin – you may be given an antihistamine
Slowing down or stopping the transfusion usually helps these symptoms.
It's rare, but it's possible to have a serious allergic reaction to a blood transfusion.
Tell your healthcare team immediately if you have any trouble breathing. They will know how to treat a serious allergic reaction.
Possible complications of a blood transfusion
A blood transfusion is a common and safe procedure.
Complications are rare but can include:
- infection – the chance of this is very low because donor blood is tested for a range of infections before it's given to you
- an allergic reaction
- having too much iron in your blood – there is a small chance of this if you have lots of blood transfusions
Complications can happen a few hours, days or even weeks after having a blood transfusion.
Urgent advice: Ask for an urgent GP appointment or contact NHS 111 if:
You have had a blood transfusion and:
- you have a high temperature or feel hot and shivery
- you have aching muscles for no reason
- you're feeling sick or vomiting
- you have blood in your pee, you're peeing very little or your pee is very dark
- you're bleeding from your mouth, bottom, nose or eyelids
- the whites of your eyes or your skin turn yellow – this can be harder to see on brown or black skin
- you have lower back pain
Tell them you recently had a blood transfusion.
You can call 111 or get help from 111 online.
Immediate action required: Call 999 if:
- you have severe difficulty breathing
- your mouth or throat is tingling or swelling
- you have chest pain
Tell them you recently had a blood transfusion.
Do not drive yourself to A&E.
The person you speak to at 999 will give you advice about what to do.
Can I donate blood after a blood transfusion?
If you've had a blood transfusion since 1980, you can no longer be a blood donor. This is a precaution against variant Creutzfeldt-Jakob disease (vCJD).
Find out more
Page last reviewed: 16 January 2025
Next review due: 16 January 2028