Valuable - universal donor - 6.6% of US donors
O-negative is the universal red-cell donor. With no A, B, or Rh-D antigens on its surface, O-negative blood can be transfused to any patient regardless of their blood type. This makes it the most critical type in emergency medicine, used whenever a patient's blood type is unknown or there is no time to test.
Antigens present
None (no A, no B, no Rh-D)
Antibodies produced
Anti-A, Anti-B
Antigens are proteins on the surface of red blood cells. Antibodies are produced by the immune system against antigens it does not carry. When incompatible blood is transfused, antibodies bind to foreign antigens and trigger a haemolytic reaction.
Select your blood type:
Can donate red cells to:
Universal donor - compatible with all 8 types
Can receive red cells from:
1 compatible type
| Population | Frequency |
|---|---|
| US blood donors (Red Cross estimate) | 6.6% |
| Global population (estimate) | 7.2% |
O-negative makes up approximately 6.6% of US blood donors according to the American Red Cross. This relatively low frequency, combined with extraordinarily high demand in trauma and emergency surgery, means O-negative blood is perpetually in short supply. If you are O-negative, donating regularly is one of the most impactful contributions you can make to your community's blood supply. Whole blood can be donated every 56 days; Power Red (double red cell) donation is available every 112 days.
Several large epidemiological studies have observed that people with blood group O may have a modestly lower risk of venous thromboembolism (blood clots) compared with non-O types, possibly due to lower levels of von Willebrand factor. Conversely, O types may have a slightly higher risk of bleeding. These associations are statistical in nature and do not change clinical management for any individual. O-negative individuals with the Rh-null phenotype (exceptionally rare) are in a special category with unique transfusion needs. Always discuss your specific clinical situation with your physician.
Note: Associations between blood type and disease risk are from observational studies and are not deterministic. They do not change your clinical management. Cite any specific associations with your clinician.
O-negative mothers are Rh-negative. If the father is Rh-positive, the baby may be Rh-positive, creating a risk of Rh sensitisation during delivery. Anti-D immunoglobulin (RhoGAM) is routinely given at around 28 weeks and within 72 hours of delivery to prevent the mother's immune system from forming anti-D antibodies. This prophylaxis has reduced Rh sensitisation rates from 10-20% to under 1%. If you are O-negative and pregnant, ensure your obstetrician is aware of your blood type at your first antenatal appointment.
Full Rh factor pregnancy guide +For solid organ transplant, O-negative follows the same ABO compatibility rules as red-cell transfusion. An O-negative individual can donate an organ to any recipient - the universal donor principle applies here too. As a recipient, O-negative patients can only receive organs from other O-negative donors. This is a significant constraint: O-negative patients on transplant waiting lists have a narrower pool of compatible donors and may wait longer. Paired kidney exchange programs can help bridge some incompatibilities when a willing living donor exists.
ABO compatibility for organ transplant follows the same rules as transfusion - O- can donate organs to: O+, O-, A+, A-, B+, B-, AB+, AB-. However, HLA tissue matching and crossmatch testing are also required, and sensitisation from prior transfusions or pregnancies can restrict compatibility further.
Full organ transplant guide +O-type plasma contains both anti-A and anti-B antibodies. This makes O plasma the most restricted in terms of plasma donation - O plasma is only safe for O recipients. For plasma donation, AB-type donors are preferred because AB plasma has neither anti-A nor anti-B antibodies and can be given to any patient. If you are O-negative, your most valuable contribution is whole blood or red cell donation rather than plasma donation.
Note: Plasma compatibility rules are the inverse of red-cell rules because plasma carries antibodies, not antigens. AB plasma is the universal plasma donor.
Plasma compatibility chart +