Simple blood transfusion

A simple blood transfusion, (also known as a 'top-up') is a treatment used for sickle cell disease


Blood is made up of different types of blood cells and plasma (a straw-coloured liquid, which carries the blood cells around your body). 

The different types of blood cells are:

  • red cells, which contain haemoglobin (the red pigment which carries oxygen to, and carbon dioxide from, the rest of the body)
  • white cells, which fight infection
  • platelets, which are clotting cells

The adult human body contains about 5 litres of blood. Usually, red cells last about 120 days (about 4 months) in the blood. They last for a shorter time in people with sickle cell disease. The red cells are then removed by the body, which means that your body always needs to replace them.

How a blood transfusion works

A blood transfusion is a procedure that puts red cells into your body. This could be a planned procedure or be done in an emergency situation.

During a simple blood transfusion, a few units (bags) of blood are given through a small tube (drip), usually placed in a vein through your arm. 

An exchange blood transfusion (EBT) is another type of blood transfusion, used for sickle cell disease. During an EBT, sickle blood is replaced with blood from a donor who does not have sickle cell disease.  

Why a simple blood transfusion is needed

A simple blood transfusion might be needed if your haemoglobin level falls too low. This can happen during a sickle cell crises, which destroys your red blood cells.

Other reasons for needing a simple blood transfusion are:

  • if you are getting ready for an operation, to lower the chance of complications from the general anaesthetic and the surgery
  • if you are pregnant, to lower the chance of complications to you and your baby


Some of the benefits of a simple blood transfusion are: 

  • feeling more healthy
  • having fewer problems with your sickle cell disease

Simple blood transfusions can also reduce the risk of a stroke.


As with any procedure, having a simple blood transfusion does have some risks and side effects, and it is important that you understand them

Blood safety

In the United Kingdom, we take many precautions to make sure any blood given to you is as safe as possible. 

The main risk from a transfusion is that you could be given the wrong blood by accident. To make sure you receive the right blood, the clinical staff must make careful identification checks. They will ask you to state your full name and date of birth and will check the details on your name band. This is to make sure you receive the correct blood. They will also regularly monitor you during the transfusion (check your blood pressure, temperature, pulse and breathing rate) and ask you how you are feeling.

The risk of contracting a disease, such as hepatitis B and C, or human immunodeficiency virus (HIV), is extremely low. 

  • The risk of getting hepatitis B is about 1 in 900,000, and 1 in 30 million for hepatitis C.
  • The chance of HIV infection from a blood transfusion is less than 1 in 6.5 million.

Creutzfeldt-Jakob disease  is a rare, uncurable brain disease. The possibility of a blood transfusion transmitting variant Creutzfeldt-Jakob disease is extremely small and precautions are taken to reduce this risk.

We now strongly advise that all patients on a transfusion programme are routinely vaccinated against hepatitis B. During the transfusion programme, your immunity to hepatitis B and other viral infections will be regularly reviewed. 

Although the risk of contracting an infection from blood is very low, we recommend that we check you for HIV and hepatitis C infection once a year.

Antibodies against the donor blood

Your blood is matched very closely with the blood of the donor (the person who donated the blood). However, it is possible to develop antibodies against the donor blood, so you need to make the clinical staff aware of any symptoms you have after the transfusion. These antibodies can mean that matched blood is harder to find and can take longer to prepare.

If you have developed antibodies, you will be sent an alert card that says ‘I need special blood’. This is to help make sure that anyone treating you knows that your blood needs to be matched against them. You must show your alert card to clinical staff before you receive a transfusion and in any hospital where you are treated.

Side effects

After having a simple blood transfusion you might have some side effects.

Skin rash 

You might get a skin rash. This can be treated with antihistamines.

High temperature (fever)

You might get a high temperature (fever). This can usually be treated with paracetamol. 

Iron overload (receiving too much iron) 

This is common in people who receive repeated blood transfusions. If needed, excess iron can be removed by taking medicines (injections or tablets). 

Delayed transfusion reactions

Sometimes, a patient has a delayed transfusion reaction. This is where your body abnormally breaks down the blood you have been transfused. 

It can happen within the first 2 weeks of having a transfusion.

Go to the emergency department (A&E) immediately if:

  • you have severe generalised sickle cell pain or crisis
  • you notice blood in your pee (urine), which is a red or cola colour
  • you feel more tired than usual
  • you feel short of breath
  • you have a high temperature (fever)
  • you have a pain in your back

If you have any of these symptoms after you have had a transfusion, it can be a sign of a delayed transfusion reaction and will need immediate assessment. 

You must also tell the medical staff at the hospital that you have had a blood transfusion recently.

If you do not want a blood transfusion

Some people do not want to have blood transfusions, for various reasons.

We would encourage you to discuss any concerns you have about blood transfusions with the sickle team. This is important if you have had severe complications of your sickle cell disease before, or are planning a pregnancy or an operation. This is to allow the haematologist looking after you to consider if there are any alternative treatments that could be offered. The haematologist will make sure your wishes are included in your medical notes. This will be shared with other medical professionals who may be involved in your care to form a plan. We would also encourage you to discuss your objections or wishes with your family members, and in particular your legal next of kin. This is because they may be asked about your wishes regarding blood transfusion if you become unwell. 

We want to involve you in all the decisions about your care and treatment. It is entirely your choice whether to have the transfusion programme or not. We will give you relevant information to help you come to a decision with the sickle cell team. It is important that you understand the information and have the time to ask questions and to make your decision.

If you agree to have the transfusion, you will be asked to give consent and this will be documented on your medical notes. This confirms that understand what the treatment involves, and agree to have it.

If you have agreed to repeated blood transfusion, your consent will be reviewed at least every 6 months. It is up to you if you want to stop having the transfusions. If you do, it is important to discuss this with your haematologist, so that you are clear about how your decision may affect you. Other suitable treatments for you can also be discussed and offered to you at this time.

Read more about our consent process

Resource number: 1978/VER4
Last reviewed: January 2024 
Next review due: January 2027 

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