Blood types
Key facts
- Your blood type is set by antigens on the outside of your blood cells.
- Your blood group is set by genes passed to you by your parents.
- Your blood type has two parts – the ABO group and the Rhesus group.
- If you have a blood transfusion that is incompatible with your blood type, your immune system will attack the new blood.
What are blood types?
Your blood type (or blood group) is set by the chemical structures on the outside of your red blood cells. These chemical structures are called antigens.
An antigen is recognised by your immune system. An antigen that is not known by your immune system is destroyed by antibodies.
The genes you inherit from your parents decide your blood type.
What are the different blood types?
Your blood group depends on your ABO group, and your Rhesus group.
ABO blood group
There are 4 different blood types — A, B, AB and O. These names tell you whether your red blood cells carry the:
- A antigen — Type A
- B antigen — Type B
- A and B antigens — Type AB
- neither antigen — Type O
Rhesus group
The Rhesus group (Rh group) contains around 50 different antigens found on the surface of your red blood cells.
The most important antigen in the group is RhD.
Each of the 4 blood groups can be classified as either:
- Rhesus-positive — you have the RhD antigen
- Rhesus-negative — you don't have the RhD antigen
More than 4 out of 5 Australians are Rhesus positive.
Blood types in Australia
The most common blood type in Australia is O positive (O+) and the least common is AB negative (AB-).
The table below lists each of the blood type and shows:
- how common it is across the Australian population
- what blood types they are compatible with
| Blood type | How many Australians have it | Compatible blood types |
|---|---|---|
| O+ | 38% | O-, O+ |
| O- | 7% | O- |
| A+ | 32% | A+, A-, O+, O- |
| A- | 6% | A-, O- |
| B+ | 12% | B+, B-, O+, O- |
| B- | 2% | B-, O- |
| AB+ | 4% | AB+, AB-, A+, A-, B+, B-, O+, O- |
| AB- | 1% | AB-, A-, B-, O- |
O- blood can be safely given to people with any blood type.
Why should I know my blood type?
Knowing your blood type means that you can:
- have a safe pregnancy
- help others when there are blood shortages
You may be able to find out your blood type by using My Health Record.
If you don't know your blood type, you can book a blood donation to find out.
Blood type and blood transfusions
If you need a blood transfusion, your blood will be tested to make sure the donor blood you receive is compatible (mixes safely).
Blood from a different blood type has different antigens. This means that when your immune system recognises the donor blood cells, it could attack them.
If you need a blood transfusion, in an emergency and there is no time to match your blood type, you will get O- blood. This is because O- blood has no antigens and can be safely given to anyone.
Receiving the wrong blood type in a transfusion can be life threatening and you would need treatment quickly. However, it's extremely rare for this to happen.
Blood type and pregnancy
It's also possible for a pregnant person and their baby to have incompatible blood types. If you have a different blood type to your baby, you may need treatment while pregnant.
You may have a Rhesus negative blood type while your unborn baby has a Rhesus positive blood type. This can lead to Rhesus factor disease.
Rhesus factor disease is when your immune cells attack your baby's rhesus positive cells. This can lead to severe anaemia or death of the baby.
This can be prevented by treating you with anti-D immunoglobulin. This neutralises your baby's rhesus positive blood cells in your blood stream and stops your immune system making antibodies.
Donating blood
Donated blood is always needed. If you want to donate blood, visit the Lifeblood website to find a donor centre and book an appointment.
You can also donate plasma which is vital for patients with:
Plasma can also be given to a pregnant person at risk of Rhesus factor disease.
Donating blood can save someone else's life. It can also be used in different medical treatments, depending on your blood type.
Resources and support
Visit the Australian Red Cross Lifeblood website or call 13 14 95 to:
- learn more about blood groups
- find out if you're eligible for blood donation
You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with you 24 hours a day, 7 days a week.
Learn more here about the development and quality assurance of healthdirect content.
Last reviewed: September 2025
