The Rarest and Most Common Blood Types, and the Universal Donor

What are the eight blood types?

Your blood type depends on whether two antigens, A and B, are on the surface of your red blood cells, which gives four groups: A, B, AB and O. Add the Rh factor, present (+) or absent (-), and you get the eight common blood types. Your blood type is inherited from your parents, like eye colour.

Work out your baby’s likely blood type with the baby blood type calculator.

Who is the universal donor, and who is the universal recipient?

• O negative: the universal red cell donor, used in emergencies before the patient’s blood type is known.
• AB (positive and negative): the universal plasma donor, because the rules for plasma are the reverse of those for red cells.
• AB positive: the universal recipient, who can receive red cells from every blood type.

See who your blood type can give to and receive from in the blood type compatibility chart.

Which blood types are most common and rarest?

Source: Stanford Blood Center. The figures in your country may differ.

The shares vary between populations: the American Red Cross says about 45% of Caucasians are type O, against 51% of African Americans and 57% of Hispanics. So there is no single right figure for every Arab country.

What makes a blood type rare?

Besides A, B and Rh, more than 300 other antigens are known. A blood type is rare if you lack an antigen that 99% of people have, and extremely rare if you lack one that 99.99% of people have.

Why is type O always in demand?

Because O positive is the most common type, so many patients need it, and O negative is the universal type used in emergencies and for newborns with weak immune systems. But every blood type is needed, and every donation can save a life.

How do you find out your blood type?

With a simple blood typing test at any lab, the same test done before you give or receive blood. Many donation centres also tell donors their blood type.

Frequently asked questions

Sources

This guide is based on the following published sources:

1. Blood Types Explained American Red Cross
2. AB Positive, AB Negative Blood American Red Cross
3. Blood Types Stanford Blood Center
4. Blood typing MedlinePlus (US National Library of Medicine)

Content and links last reviewed: 17 October 2026. How we write the tools

This tool gives general guidance based on published rules, which differ by country and change over time. It does not replace a medical assessment. The doctor at the donation centre always makes the final decision. In an emergency, call your local emergency number.