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Blood transfusions

Each year about two million units of blood are transfused in England. A unit of blood is about a quarter of a litre.

Why might I need a blood transfusion?

You might need a blood transfusion if you have lost blood in an accident or during an operation. It might also be used if you have severe anaemia. People with anaemia don’t make enough red blood cells and may need a blood transfusion.

Where does the blood come from?

In the UK, National Health Service Blood and Transplant (NHSBT) collect donations from volunteers and carefully check these for infections.

What will happen?

A sample of your blood is taken before you have a tranfusion and sent to the laboratory. Donor blood will be selected that is compatible with your own blood group. There are four main blood groups: A, B, AB and O. These are important if you are having a blood transfusion as the donor's blood group must be compatible with your own.

You will need to wear an identification band showing all your details. This checked against each bag of blood before it is given to you. It is very important that you wear this band to avoid any mistakes.

The blood transfusion is usually given through a tube called a cannula, which is inserted into a vein in your arm. The tube is connected to a giving set, which is attached to the bag of blood. The blood runs through this giving set into your vein. If you need several transfusions it may be given through a vein in your chest (a central line).

How long will it take?

Bags of blood hold about a quarter of a litre, which usually takes about one to two hours to run into your arm. It can sometimes take up to four hours

Does it hurt?

Most people don’t feel anything during the blood transfusion. Some people get a temperature, a rash on their skin, or a headache. You must tell the nurse about any side effects so that treatment can be provided.

Looking forward

If you are having an operation in hospital, make sure you eat a well-balanced diet in the run up to it. Your GP will also be able to give you advice about improving your iron intake. A good diet, enriched with iron, will lessen your chances of needing a blood transfusion after an operation.

More information

Useful links

Link to Living with spinal muscular atrophy and scoliosis by Chrystal, 13
Link to Crohn's Disease Podcast

Last reviewed by Great Ormond Street Hospital: 17 March 2011