What Is Special About Blood Type O Positive?

Medically Reviewed on 12/19/2022
o positive blood type
People with blood group O-positive can donate blood to other O-positive people, as well as all other positive blood types (A+, B+, and AB+).

Blood group O-positive (O+) is the most common blood type among Americans.

  • About 43 percent of Americans have an O blood type of which O-positive accounts for about 38 percent of the population.
  • It is also the most needed blood type because it is most commonly required during blood transfusions. 

People with blood group O-positive can donate blood to not only other O-positive people but also all other positive blood types (including A+, B+, and AB+). More than 80 percent of people have a positive blood type, making O-positive blood in high demand. It is, thus, also the blood type whose shortage may occur often owing to its huge need.

  • During emergencies in patients with unknown blood groups requiring blood transfusion, O-positive blood is the preferred type to be transfused.
  • This may be done in patients with severe injuries such as road traffic accidents and other emergencies.
  • The O-positive blood type is preferred because it has minimal risk of reactions and because it is more readily available than the O-negative blood group.

Cytomegalovirus (CMV)-negative people with an O-positive blood group are also called “heroes for babies.” CMV negative means those individuals who have not been exposed to cytomegalovirus. O-positive and CMV-negative blood type is the safest blood type that can be transfused to immunocompromised newborns.

Although O-positive people can donate blood to people with any positive blood type, they can only receive blood from O-positive and O-negative (O−) people. 

Research suggests that people with blood group O have a lower risk of heart diseases and memory problems (including dementia) than the rest of the population.

What are the various blood types?

Your blood group is determined based on the presence or absence of certain substances, called blood group antigens, on the surface of your red blood cells (RBCs).

Your blood group is determined by the genes you inherit from your parents. There are two major blood group antigens called “A” and “B.”

  • If your RBCs have A antigen on their surface, you are said to have blood group A.
  • If B antigen is present instead of A on the surface of your RBCs, you are said to have blood type B.
  • If both A and B antigens are present, the blood type is called AB.
  • In individuals where both A and B antigens are absent, the blood type is called the O blood group.

Besides these antigens, there is a protein called the Rh factor whose presence or absence decides whether your blood type is negative or positive. For example, if you have A antigen and Rh factor on your RBCs, your blood type will be A positive (A+); however, if A antigen is present but the Rh factor is absent, your blood type will be called A negative (A−). 

The various blood types are explained in the table below:

Table. Various blood types and their blood group antigen and Rh factor
Blood type Blood group antigen Rh factor
A+ A present, B absent Present
A− A present, B absent Absent
B+ B present, A absent Present
B− B present, A absent Absent
AB+ Both A and B antigens present Present
AB− Both A and B antigens present Absent
O+ Both A and B antigens absent Present
O− Both A and B antigens absent Absent


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Which blood group is called the universal donor?

The blood group O-negative is called a universal donor because it can donate blood to any person regardless of their blood type. It is also used for blood transfusion in newborns.

Like donors who are O-positive with CMV negative, people with O-negative blood type who is also CMV negative are called heroes for babies at the red cross society. 

People with O-negative blood groups can only receive O-negative blood, which is a blood group that is high in demand. It is present in a mere 7 percent of the population.

  • Due to its relative rarity and high demand, blood group O-negative is often met with a shortage.
  • Hence, healthy people with this blood type O-negative are encouraged to donate blood and contribute to saving many lives.

Data suggest that although 50 percent of the US population is eligible to donate blood, a mere 5 percent donate blood. If you are among the eligible population, you must consider donating blood so that it may be used when someone needs it.

Before the blood groups were discovered, people were transfused blood without matching or typing. This resulted in several complications and even deaths.

Blood transfusion these days is only done after blood typing. Hence, people with certain blood groups can only donate to and receive from specific blood groups.

Table. Blood group transfusion
Blood group Can donate blood to Can receive blood from
A+ A+, AB+ A+, A−, O+, O−
A− A+, A−, AB+, AB− A-, O−
B+ B+, AB+ B+, B−, O+, O−
B− B+, B−, AB+, AB− B−, O−
AB+ AB+ All blood group types
AB− AB+, AB− AB-, O−, A−, B−
O+ O+, A+, B+, AB+ O+, O−
O− All blood group types O−

Because people with blood group AB positive can receive the blood of any blood group type, they are also called universal recipients. Furthermore, the AB blood type is also called a universal plasma donor, as people with this blood group can donate their plasma (the liquid that remains after blood cells are removed from the blood) to people with any blood type. 

Plasma donation is needed in several conditions such as burns, shock, severe injuries, cancer, certain liver diseases, and certain blood clotting factor diseases.

AB− blood group is the rarest blood type occurring in just 0.6 percent of the US population, whereas the AB+ blood group is present in about 3.4 percent of the people in the United States.

Which blood group is more likely to get COVID-19?

Studies report that there is no relationship between your blood type and the risk of COVID-19 infection. Your blood group also does not influence the risk of having a severe form of COVID-19.

Initially, some studies indicated that some blood groups are more susceptible to COVID-19. These findings, however, have been refuted after analysis of a larger database.

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Medically Reviewed on 12/19/2022
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