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.

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:

1. You will sit in a chair or lie on a bed.
2. A thin plastic tube is inserted into a vein in your arm.
3. The tube is then attached to a bag of blood (called a drip).
4. Blood slowly flows into your body from the drip.
5. 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.

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.

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.

Ask for an urgent GP appointment or contact NHS 111 if:

Call 999 if:

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

• NHS Blood and Transplant: blood services, blood donation and blood transfusion