How Blood Type Is Determined And Why You Need To Know
Blood types are determined by the presence or absence of certain antigens – substances that can trigger an immune response if they are foreign to the body. Since some antigens can trigger a patient’s immune system to attack the transfused blood, safe blood transfusions depend on careful blood typing and cross-matching. Do you know what blood type is safe for you if you need a transfusion?
There are four major blood groups determined by the presence or absence of two antigens – A and B – on the surface of red blood cells. In addition to the A and B antigens, there is a protein called the Rh factor, which can be either present (+) or absent (–), creating the 8 most common blood types (A+, A-, B+, B-, O+, O-, AB+, AB-).
Type A Negative
Only 1 in 16 people have A negative blood.
If you have A negative blood you can donate to anyone with a blood type of A or AB regardless of the positive or negative, however if you have A negative blood you can only receive A- or O- blood.
Type A Positive
1 in 3 people are A positive, which is why it is one of the most common blood types.
As you can imagine A positive blood is in high demand, because it is presence in a large percentage of the population.
Patients undergoing chemotherapy treatments also have a high demand for the platelets from those with the A positive blood type
Type B Negative
Less than 2% of the population have B negative blood.
B negative red blood cells can be given to both B and AB patients. B negative patients can only receive blood from other B negative donors or from type O negative donors (who are the universal donors). Since both of those types are fairly rare, the Red Cross works hard to ensure that sufficient supplies are always available.
Type B Positive
About 9% of the population have B positive blood.
B positive red blood cells can be given to both B positive and AB positive patients.
B positive patients can receive blood from B positive, B negative, O positive and O negative donors.
Type O Negative
O negative is the most common blood type used for transfusions when the blood type is unknown. This is why it is used most often in cases of trauma, emergency, surgery and any situation where blood type is unknown. O negative is the universal blood type.
O negative blood type can only receive O negative blood.
O negative donors who are CMV negative are known as Heroes for Babies at the Red Cross because it is the safest blood for transfusions for immune deficient newborns.
Only 7% of the population have O negative blood. Due to the its versatility for transfusions, it is in high demand. In an emergency, it is the blood product of choice. For example, just one car accident victim can require up to 100 units of O neg. Meeting the demand for O negative blood is always a priority for the Red Cross.
O negative is the first blood supply to run out during a shortage due to its universality.
Type O Positive
Type O positive blood is given to patients more than any other blood type, which is why it’s considered the most needed blood type.
38% of the population has O positive blood, making it the most common blood type.
O positive red blood cells are not universally compatible to all types, but they are compatible to any red blood cells that are positive (A+, B+, O+, AB+).
Over 80% of the population has a positive blood type and can receive O positive blood. That’s another reason it’s in such high demand.
In major traumas with massive blood loss, many hospitals transfuse O positive blood, even when the patient’s blood type is unknown. The risk of reaction is much lower in ongoing blood loss situations and O positive is more available than O negative. Type O positive blood is critical in trauma care.
Those with O positive blood can only receive transfusions from O positive or O negative blood types.
Type O positive blood is one of the first to run out during a shortage due to its high demand.
Type AB Negative
Less than 1% of the U.S. population have AB negative blood, making it the least common blood type among Americans.
Patients with AB negative blood type can receive red blood cells from all negative blood types.
Type AB Positive
Less than 4% of the U.S. population have AB positive blood.
AB positive blood type is known as the “universal recipient” because AB positive patients can receive red blood cells from all blood types.
Recent studies show that there is a need for blood transfusions every 2 seconds. The average person can only donate 1 pint of whole blood in a single donation and the shelf life is 42 days, which is why the need to keep replenishing the supply to meet demands is great. 38% of the population in the United States are eligible to donate blood, but only 3% of us actually donate.