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Blood types

3-minute read

Your blood type, also known as your blood group, is decided by the genes you inherit from your parents.

What are blood types?

Your blood type is determined by antibodies – proteins in your blood that search out foreign substances, such as germs – and by proteins found on the surface of the red blood cells.

Being given the wrong type of blood can be very dangerous. If you receive blood with the wrong sort of antigens, your body’s immune system could attack it. It is also possible for a mother and her baby to have incompatible blood types, and this will need treatment while the mother is pregnant.

If you need a blood transfusion and you don’t know your blood type, or your blood type isn’t available, then there are other blood types that can be safely given to anyone.

The different blood types

There are four different types of blood – A, B, AB and O. These names indicate whether your blood’s red cells carry the A antigen, the B antigen, both A and B antigens, or neither antigen.

Each of the 4 blood groups can be classified as either Rhesus positive or Rhesus negative. The Rhesus system looks at different antigens on the surface of the red blood cells. If you have an antigen called the RhD antigen, you are Rhesus positive, and if you don’t you are Rhesus negative. More than 4 out of 5 Australians are Rh positive.

The most common blood type in Australia is O positive and the least common is AB negative.

The table below lists each of the blood types, including how common they are across the Australian population.

Blood type How many Australians have it About this blood type
O+ 40% This is the most common blood type.
O- 9% O- can be safely given to any patient, regardless of their blood type.
A+ 31% Type A platelets (a component of blood that is important for clotting) can be safely given to any patient.
A- 7%
B+ 8% Type B is more common in South Asian and black communities.
B- 2%
AB+ 2%
AB- 1% This is the rarest blood type.


What if I need a blood transfusion?

People may need a blood transfusion if they lose a lot of blood; their blood is low in certain components such as red cells, platelets or plasma; because they have a medical condition such as cancer, anaemia or a bleeding disorder; or because they are having surgery.

If you need a transfusion, you will receive blood that has been collected by the Australian Red Cross Lifeblood from voluntary donors. All blood is rigorously checked for infections such as HIV and hepatitis. You will also have careful identification checks before the transfusion to make sure you receive the right blood type.

Receiving the wrong blood type in a transfusion is extremely rare. If you did get the wrong blood type, you could have a serious reaction. This could be life threatening so you would need treatment quickly.

Why donating blood is important

Donated blood can be turned into different medical treatments, depending on which blood type you have. For example, whole blood from type A, type O positive and type O negative is always needed. People with type AB or type B can donate plasma, which is vital for patients with injury, severe burns or blood diseases.

Donating blood can save someone else’s life. To find out if you’re eligible, and to learn more, visit the Australian Red Cross Lifeblood website or call 13 14 95.

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Last reviewed: November 2017

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