What are blood groups?

Blood groups are complex chemical systems found on the surface of blood cells. The two main blood group systems in transfusion practice are the ABO system and the Rh(D) type. Identification of the correct blood group is important to prevent reaction following transfusion.

Within the ABO system, people can be one of four groups - O, A, B or AB, while in the Rh(D) system they can be either Rh(D) positive or Rh(D) negative. Each system is inherited independently of the other. As a result, there are eight main blood groups.

The Givers/Receivers chart shows the compatibility of different blood groups. For example, an A negative patient may receive blood from an O negative or an A negative donor.

  • Rh(D) negative patients should not normally receive Rh(D) positive red cells, this is particularly important in women of childbearing age.
  • Type O is the most common blood type with around 50% of New Zealanders having this blood group.
  • Type O negative donors are referred to as "the universal donors" because in an emergency their red cells can be transfused to people who have any blood type. Because any patient can receive type O negative blood, there is a particular need for O negative donors to give regularly

Also see the Education section for learning aids to use in the classroom to educate students about blood.

O is for Extra Ordinary Leaflet (pdf, 565 KB)

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