Blood transfusion

Blood transfusion is a procedure in which you are given blood or blood products from someone else through a vein.

On this page, you can find the following information:

Key points

  1. You might need a blood transfusion because of losing a lot of blood, eg, in an emergency, or your body is not producing have enough red blood cells (anaemia) or chemotherapy is destroying your red blood cells.
  2. Your doctor will advise how much blood is needed in your situation. 
  3. Most people get better after just one unit of blood transfusion. 
  4. In New Zealand, blood only comes from unpaid or voluntary donors. 
  5. Like any other procedure, blood transfusion has its risks and complications, but it is generally a safe procedure and can save many lives. 

What is a blood transfusion?

A blood transfusion is a procedure in which you are given blood or blood products through a vein. The procedure has to be done in hospital or a healthcare facility. 

Where does blood for a transfusion come from? 

In New Zealand, blood comes only from unpaid and voluntary donors. 

Why might I need a blood transfusion?

Red blood cells are needed to carry oxygen around your body to help your body function properly. You might need a blood transfusion because you don't have enough blood or red blood cells. 

This can happen when:

  • you have lost a lot of blood in an emergency situation, eg, in an injury or surgery
  • you have lost too much blood for other reasons, eg, heavy bleeding during a menstrual period or stomach ulcers causing bleeding inside your body
  • your body is not producing enough red blood cells to carry oxygen around your body, eg, due to iron deficiency (anaemia)
  • your body is destroying too many red blood cells, eg, due to chemotherapy.

How safe is a blood transfusion?

A blood transfusion is an extremely safe procedure and treatment. It can save many lives.

Before donor blood is given to you, it is always tested and screened for infections such as HIV/AIDS, hepatitis Bhepatitis C and syphillis. Both your blood and the donor blood are also tested to check for blood group types and antibodies to avoid a reaction due to them not being compatible.

The equipment used to collect blood are all sterile and only used once. 

Your doctor will weigh the benefits against the risks of you having a blood transfusion. If your doctor recommends a blood transfusion, that will mean the benefits are greater than the risks. 

What are the different types of blood components used in a blood transfusion?

Blood components that are used in a blood transfusion include:

  • red blood cells – used to replenish the red blood cells lost in anaemia or severe bleeding
  • platelets – tiny blood cells to stop bleeding
  • fresh frozen plasma and cryoprecipitate – used to replace proteins for blood clotting.

Are extra units of blood transfusion helpful?

Your doctor will advise how much blood you need. Most people get better after just one unit of blood transfusion. However, some people will need more blood.

You may need more blood if you have:

  • severe bleeding that is hard to control
  • severe anaemia and severe chest pain

Although blood transfusion in New Zealand is generally safe, the risks increase if you get more blood. Read more about the risks of a blood transfusion

Recent research found that extra units of blood are not helpful if you don't need them. Read more about blood transfusions for anaemia in hospital – how much do you need? Choosing Wisely, NZ 

What alternatives are available? 

There are other alternatives to a blood transfusion. These include the following:

  • No transfusion – this is when the risks from not having a transfusion are greater than the risks from having a transfusion, so it is not recommended. 
  • Blood substitutes – there is no routine use of blood substitutes for red blood cells, platelets or plasma so far.  
  • Providing blood for yourself – this is also called autologous blood collection. Your blood is collected for your own use in the future. Read more about donating blood for yourself.
  • Directed donations – blood is collected from your relatives or friends. This is not recommended by the New Zealand Blood Service. 

Talk to your doctor to find out what alternative is best for you. 

What can I expect during a blood transfusion?

Your doctor or nurse will explain to you about the process of a blood transfusion, including the risks and side effects. You will need to sign a consent form if you agree to receive a blood transfusion. This is a good time to ask your health providers any questions relating to the process. Your blood sample will also be taken and tested for blood group types and antibodies and matched with donor blood to prevent a reaction due to lack of compatibility. 

Before any blood is given to you, a nurse will check your identification to ensure you are given the correct blood. Similar to a blood test, you will feel a prick or sharp sting when a needle is inserted into your vein, and some pressure when the blood is flowing into your vein. However, you should not feel any pain or discomfort during the process. A nurse will monitor you to make sure you feel fine throughout. 

The time a blood transfusion takes depends on the amount of blood you are receiving. It can range from 1–4 hours. 

What are the risks of a blood transfusion?

The risks of a blood transfusion include:

  • temporary reactions such as a mild fever or skin rash
  • an incompatibility reaction such as kidney failure, breathing difficulties and other life-threatening complications, but this is rare
  • a mild allergic reaction such as a rash or more severe allergic reaction such as fainting, breathing difficulties or cardiac arrest
  • minor virus infections, but this happens only occasionally
  • more serious infections such as hepatitis B and C, HIV/AIDS and HTLV-1 virus are very rare as screening of these infections are done before the procedure, but they can be serious and life-threatening in some cases
  • the desired effect of a blood transfusion not being achieved. 

Seek immediate medical attention from the nearest emergency department or call 111 if you or someone you care for has the following symptoms during or after the procedure:

  • fever
  • chills or cold skin
  • breathing difficulties, cough or wheeze
  • nausea, vomiting, tummy cramps or diarrhoea
  • dizziness or collapse
  • rash
  • chest or back pain
  • fast heartbeat.

Ring Healthline 0800 611 116 for advice if you are unsure what to do.

Learn more

Fresh blood components – your guide to blood transfusion NZ Blood Service
Blood transfusions for anaemia in hospital – how much do you need? Choosing Wisely, NZ 
My guide to blood transfusions NPS MedicineWise, Australia
A general guide to blood transfusion – information for patients and families Health Translations Victoria 
Blood transfusion NHS, UK 
A patient's guide to blood transfusions Cleveland Clinic, US  


  1. Fresh blood components – your guide to blood transfusion NZ Blood Service
  2. Blood transfusion Auckland Regional Health Pathways, NZ 
Credits: Health Navigator Editorial Team.