If you're going to receive a blood transfusion as part of a planned course of treatment, the doctor, nurse or midwife planning your transfusion will usually obtain your informed consent for the procedure.

In obtaining consent, they should:

• explain why a blood transfusion is required and if there are any alternatives
• explain potential risks or complications associated with the transfusion

There may be circumstances when it's not possible to obtain consent before a transfusion – for example, if someone is unconscious after a major accident.

How blood is given

A sample of your blood will be taken before the transfusion to check that the blood you receive is compatible with your own blood. Read more about blood groups.

You will be asked to state your full name and date of birth, and the details on your identification band will be checked before each bag of blood is given.

Blood is usually given through a tiny plastic tube called a cannula, which is inserted into a vein in your arm. The cannula is connected to a drip and the blood runs through the drip into your arm.

Depending on the underlying condition and the type of other treatment needed, some patients may have a larger tube, which is known as a central line, inserted into a vein in their chest.

Alternatively, a peripherally inserted central catheter (PICC line) may be inserted in the crook of the arm.

During the transfusion

There may be some discomfort when the tube is put into the vein, but you shouldn't feel anything during the transfusion.

You'll be observed at regular intervals, but if you start to feel unwell during or shortly after your transfusion, you should tell a member of staff immediately.

Some people may develop a temperature, chills or a rash. These reactions are usually mild and easily treated with paracetamol or by slowing down the blood transfusion.

Severe reactions to blood are rare. If they occur, staff are trained to recognise and treat them. If you have any concerns, discuss them with your doctor, nurse or midwife.

A single unit of blood can take between 30 minutes and four hours to be given.

Read more about the risks of blood transfusion.