Which blood type is the universal donor?
General information only. This article explains the basics and is not medical advice. For anything about your own health, talk to a doctor or other qualified professional.
Quick answer
O negative (O−) is known as the universal red blood cell donor. Its red cells have no A, B or RhD markers (antigens), so they can usually be given to patients of any blood type, which makes it vital in emergencies when there’s no time to test. Only about 7% of people in the US have O-negative blood.
How blood types work
Your blood type depends on markers called antigens on the surface of your red blood cells.
| Blood type | A antigen | B antigen | Your immune system makes antibodies against |
|---|---|---|---|
| A | ✓ | B | |
| B | ✓ | A | |
| AB | ✓ | ✓ | Neither |
| O | A and B |
A third marker, the RhD factor, makes blood positive (+) if present or negative (−) if absent. If a patient receives red cells with antigens their body doesn’t recognize, their immune system can attack them.
Why O negative works for almost everyone
O-negative red cells have no A, no B and no RhD markers, so there’s nothing for most recipients’ antibodies to react against. Hospitals and ambulances often keep O-negative blood ready for trauma cases and newborns. Before a routine transfusion, blood is still carefully tested and matched.
Universal recipient and plasma donor
| Role | Blood type | Why |
|---|---|---|
| Universal red cell donor | O− | No A, B or RhD antigens |
| Universal red cell recipient | AB+ | Has all three antigens, so no antibodies against them |
| Universal plasma donor | AB | Its plasma has no anti-A or anti-B antibodies |
How common is each type?
In the US, roughly:
| Type | Share of people |
|---|---|
| O+ | 37% |
| A+ | 36% |
| B+ | 9% |
| O− | 7% |
| A− | 6% |
| AB+ | 3% |
| B− | 2% |
| AB− | 1% |
Percentages vary by country and ancestry.
Who discovered blood types?
Austrian scientist Karl Landsteiner discovered the A, B and O groups in 1901, making safe transfusions possible. He won the Nobel Prize in 1930. To learn more about donating, contact your national blood service.
For what other blood cells do, see what white blood cells do.
Sources
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