Blood types are determined by the presence or absence of certain antigens, a molecule or molecular marker that the immune system can recognize as either part of the body or as a foreign intruder. The existence or absence of two antigens, A and B, on the surface of red blood cells determines the four main blood groups:
- Type A: Has only A antigens on the red blood cells.
- Type B: Has only B antigens on the red blood cells.
- Type AB: Has both A and B antigens on the red blood cells.
- Type O: Has neither A nor B antigens on the red blood cells.
Additionally, there is a protein called the Rh factor, which can be either present (+) or absent (–), creating the eight most common blood types: A+, A-, B+, B-, AB+, AB-, O+ and O-. Your blood type is inherited from your parents, like other genetic traits such as eye color or hair type.
Blood typing and cross-matching are critical to safe blood transfusion because antigens can active the body’s immune system, and in some cases, attack transfused blood. Some blood types are not compatible, and hospitals must give the correct blood type in a transfusion. Using the wrong blood type can cause serious health problems or even death. That’s why donations from all blood types are important.
Check out the interactive pie chart to the right to learn more about the eight main blood types. Other antigens exist that create what are considered rare blood types outside the main eight types. To learn more about those blood types, check out the rare blood types section below.
You do not need to know your blood type to donate blood. As a matter of fact, a benefit of donating blood is learning your blood type post-donation.
Is One Type More Valuable Than Another?
Donations of all blood types are needed to help save lives. Sometimes a particular blood type will be in short supply and donations for that blood type will be urgently needed.
Type O-, often called the “universal” blood type, is almost always in demand because O- red blood cells can be transfused to anyone regardless of their blood type.
People with Type AB blood are universal plasma donors because their blood plasma can be used by anyone. Blood plasma is used to help trauma and burn victims, people with clotting problems, leukemia patients and many others. This is the rarest blood type, occurring in only 5% of the population.
Your donation of red blood cells, platelets, or plasma can make a lifesaving difference for someone in our community. While all blood types are needed, some are more conducive to particular types of blood donations, such as platelets or double red cells. Ask your phlebotomist the best way you can save a life.
Why Your Donation Matters
When you donate blood with Kentucky Blood Center, know that your donation will be maximized to help save as many local lives as possible. When a donor makes a whole blood donation, in most cases that product will be separated into individual components to address specific needs of patients in Kentucky. Different conditions call for different treatments. Among the many reasons why a donor may need blood include:
- Trauma
- Cancer
- Disease
- Blood disorder
- Surgery
- Organ transplant
- Childbirth
One in four people will need a blood transfusion in their lifetime, and someone in the U.S. needs blood every two seconds. In 2023, there were 10,328,000 red blood cell transfusions, 2,220,000 platelet transfusions, 1,882,000 plasma transfuions and 1,171,000 cryoprecipitate transfusions.
To meet the various needs of patients at more than 70 hospitals, KBC needs 400 donors a day.
Rare and Uncommon Blood Types
While most people fit into the eight blood groups, not everyone fits into those main types. There are more than 35 other blood groups and more than 600 other known antigens.
Matching matters, and whether you fall into one of the main eight blood groups or have a special mix of proteins and sugars (antigens) that give you a rare blood type, KBC is committed to ensuring blood is available for every type of blood.
To learn more about rare and uncommon blood types, click below.
