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. The ABO antibodies (anti-A and anti-B) are naturally occurring - present from infancy against whichever A or B antigen you lack. The Rh anti-D antibody is different: Rh-negative people do not carry it from birth and only form it after exposure to Rh-positive blood through transfusion or pregnancy (sensitisation), which is why anti-D immunoglobulin is given to prevent it. 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 around 13-16% 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 +Updated 2026-04-27