Not all blood is the same. Blood type, also called blood group, is determined by the presence or absence of specific antigens, which can be proteins, carbohydrates, glycoproteins, or glycolipids. Blood type is particularly important during blood transfusions because some blood types are incompatible with one another. If a patient receives an incompatible blood type, their body will attack it like a life-threatening infection rather than a life-saving transfusion.
Blood falls into one of four major blood groups depending upon the presence or absence of two antigens—named A and B—on the surface of its red blood cells (and the opposite antibodies in its plasma). In addition, blood is further classified as either positive (+) or negative (-) depending upon whether it contains a protein known as the Rh factor. Together, the ABO system and the Rh system give us the eight main blood types:
- A positive (A+) — Can donate cells to A+ and AB+
- A negative (A-) — Can donate cells to A+/- or AB+/-
- B positive (B+) — Can donate cells to B+ and AB+
- B negative (B-) — Can donate cells to B+/- and AB+/-
- O positive (O+) — Can donate cells to A+, B+, AB+, and O+
- O negative (O-) — Can donate cells to all types (universal donor)
- AB positive (AB+) — Can donate cells to AB+
- AB negative (AB-) — Can donate cells to AB+/-
As shown above, Type O- blood can be used in transfusions for any blood type. Type O blood is constantly in high demand in hospitals because O- is the universal donor and O+ is the most common blood type. The least common blood types are B- and AB-. Also note that blood group compatibilities are reversed for plasma transfusions. So AB+, which can only donate cells to AB+ patients, becomes a universal plasma donor. Meanwhile O-, the universal cell donor, can only donate plasma to O- patients. In the United States, type O- is the most common blood type. Broken down by race, type O-’s prevalence is 37% among Caucasians, 47% among African Americans, 39% among Asians, and 53% among Latino-Americans, according to the American Red Cross.
The 10 countries with the highest percentage of type O+ blood:
- Chile (85.5%)
- Ecuador (75.0%)
- Peru (70.0%)
- Zimbabwe (63%)
- El Salvador (62.0%)
- Colombia (61.3%)
- Democratic Republic of the Congo (59.5%)
- Mexico (50.09%)
- Venezuela (58.3%)
- Honduras (57.5%)
The 10 countries with the highest prevalence of type A+ blood:
- Armenia (46.3%)
- Norway (41.6%)
- Malta (41.0%)
- Cyprus (40.35%)
- Portugal (39.8%)
- Japan (39.8%)
- Uganda (39.0%)
- Cameroon (38.8%)
- Switzerland (38.0%)
- Turkey (37.8%)
The 10 countries with the highest prevalence of type B+ blood:
- India (38.14%)
- Thailand (36.8%)
- Bangladesh (34.58%)
- Pakistan (34.40%)
- Myanmar (32.7%)
- Vietnam (30.8%)
- North Korea (30.15%)
- Indonesia (28.85%)
- Malaysia (27.37%)
- Nepal (27.1%)
The 10 countries with the highest prevalence of type AB+ blood:
- Bangladesh (16.85%)
- North Korea (11.32%)
- South Korea (10.98%)
- Japan (9.9%)
- Pakistan (9.52%)
- India (8.93%)
- Nepal (8.6%)
- Kazakhstan (8.3%)
- Hungary (8.0%)
- Indonesia (7.96%)