Blood transfusions

Cancer treatments can reduce the number of red blood cells in the blood. This is called anaemia. Sometimes cancer can also cause anaemia.

Anaemia can cause feelings of fatigue and breathlessness. This is because without enough red blood cells, the body doesn’t have enough haemoglobin. Haemoglobin is a substance that carries oxygen through the body.

A blood transfusion can relieve the symptoms of anaemia. You will be given blood by a drip into one of your veins. This will increase the number of red blood cells in your blood.

You may be given the transfusion as an outpatient, or you may need to stay in hospital overnight. This depends on how much blood you need to be given. You should feel the benefit of the transfusion within 24 hours.

Because all blood supplies are carefully screened, complications and infection are very rare. But if you have any questions or concerns, please ask your doctor or nurse.


Anaemia is a low number of red blood cells. Many people with cancer will develop it at some point during their illness. This can be due to the cancer or caused by cancer treatment, including chemotherapy and radiotherapy.

If the number of red blood cells in your blood is low, you may become very tired and feel like you have no energy. You may also become breathless. This is because the red blood cells contain haemoglobin (Hb), which carries oxygen around the body.

You will have a blood test to check your haemoglobin level if you have symptoms of anaemia or are having cancer treatment. This is known as a full blood count (FBC). Your doctors may recommend that you have a blood transfusion if your haemoglobin level is low.

Blood transfusions

Blood transfusions are a simple way of treating anaemia. A blood transfusion involves having blood from carefully screened donors.

The transfusion increases the number of red blood cells in your blood, which means that more oxygen can be carried around the body to the tissues and organs. You will have more energy and be less breathless. You should notice an improvement in your symptoms within 24 hours of having the transfusion. But for some people, the benefits may only be temporary and they may need more transfusions.

Before you have a transfusion, your doctor will explain the aims of the treatment to you. They will also give you information to read. This is available in many languages and in large print. You will usually be asked to sign a form saying that you give your permission (consent) for the hospital staff to give the blood transfusion. No medical treatment can be given without your consent.

You may decide not to have a transfusion. It’s important to tell a doctor or your nurse if you decide not to have treatment, so that they can record your decision in your medical notes. You don’t have to give a reason, but it can be helpful to let the staff know your concerns so that they can give you the best advice.

Jehovah’s Witnesses may choose not to accept some types of blood products. If this affects you, talk to your doctor about other treatments or ways of managing your anaemia.

Having a blood transfusion

If you need a blood transfusion, your blood will be cross-matched.  To do this, the doctor or nurse takes a sample of your blood. This is used to find your blood group. This is then closely matched to donor blood. The tests used to cross-match are to make sure the blood is the best match for you and will not make you unwell.

The blood for transfusion is stored in small plastic bags. Each bag is called a unit of blood. You will usually have 2-4 units of blood depending on how anaemic you are.

Blood is given by a drip (infusion) into one of your veins. A nurse will put a short thin tube (cannula) into a vein in your arm or hand. This is then connected to a drip. If you have a central line or PICC line in place for other treatments, your nurse can connect this to your drip instead.

Transfusion of each unit of blood can take up to 4 hours. If you are having 1-2 units of blood, you can usually have it at an outpatient clinic. If you need several units you may need to stay in hospital overnight.

Possible side effects of blood transfusions

Reactions to blood

During the transfusion, you will have your temperature, pulse and blood pressure checked regularly by the nurses. This is to make sure you are not having a reaction to the blood. Common mild reactions can be headaches, a slight rise in temperature or a skin rash. These effects can be relieved by drugs such as paracetamol or by slowing the transfusion down.
Severe side effects from blood transfusions are rare because blood is cross-matched first. The nurses will check you for any reactions. They’ll stop the transfusion and quickly treat any symptoms. Tell your nurse straightaway if you have any chest or back pain, feel sick or are short of breath during your transfusion. Contact the hospital if you have any problems after you get home.

Fluid overload

Rarely, the amount of fluid given in a blood transfusion may put a strain on a person’s heart. This is more likely in people who have a heart condition. If you have heart problems, it may be more difficult to get rid of any extra fluid. Your doctor will give you medicine to help you pass more urine (a diuretic) to help with this.

Tell your doctor or nurse straightaway if you have puffiness or swelling in your hands or feet, or feel short of breath.

Iron overload

Red blood cells contain a small amount of iron. If you have lots of blood transfusions over many months, there’s a very small risk that the iron can build up in your body (called iron overload). If you are at risk, you can have treatment to stop it happening. Your doctor or nurse will explain more about this.

Are blood transfusions safe?

Some people worry that the blood they are given may be infected by disease. People who donate blood are carefully screened for infection or viruses such as hepatitis or HIV. This is to make sure the blood they donate is as safe as possible. All donated blood is tested in the laboratory for infection. Rarely, these tests fail to find an infection, but the risk of being given infected blood is extremely small.

Checking your details

When your blood is cross-matched the nurse will record your name, date of birth, and identification number on the sample.

The nurses will check your details including your blood group several times before they give you a blood transfusion. This is to make sure you are getting the blood that’s matched for you. Before this, they put an identification band on your wrist with details of your name, date of birth and identification number. They check this carefully and also ask you to give your full name and date of birth, before each bag of blood is given.

If you have any concerns about receiving a blood transfusion, talk these over with your doctor or specialist nurse.

Irradiated blood

After some cancer treatments, such as certain chemotherapy drugs or after a stem cell transplant, any blood transfusions you have must be treated first with radiation (irradiated). Your doctor will tell you if this applies to you.

Irradiated blood lowers the risk of the donated blood cells reacting against your own. The radiation won’t damage the blood or make you radioactive. Your doctor will record in your medical notes if you should only have irradiated blood products. They’ll also give you a card to carry in case you’re treated at another hospital. Keep this card with you at all times and remind your hospital team that you need irradiated blood or platelets.

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