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Blood Type Information

What is a blood group?

All people belong to one of four inherited blood groups: A, B, AB, and O. The letters A and B refer to the kind of antigen found on an individual's red blood cells. An antigen is a protein on the cell which triggers an immune response, such as the formation of antibodies, against the antigens which the red cell lacks. For example, a group A individual, when exposed to B antigens, will produce anti-B antibodies.

How is my blood group determined?

You inherit your blood group from your biological parents. This chart shows the potential blood groups you may inherit from your parents.

BLOOD TYPE INHERITANCE
IF PARENTS' BLOOD GROUPS ARE

PARENT 1 

AB

AB

AB

AB

B

A

A

O

O

O

PARENT 2

AB

B

A

O

B

B

A

B

A

O

POSSIBLE CHILDREN'S BLOOD GROUP

O

-

-

-

-

X

X

X

X

X

X

A

X

X

X

X

-

X

X

-

X

-

B

X

X

X

X

X

X

-

X

-

-

AB

X

X

X

-

-

X

-

-

-

-

What are the four basic groups in the ABO system, and what do the group names mean?

Group A
Blood has A antigen on red cells, and anti-B antibody in its plasma.

Group B
Blood has B antigen on red cells, and anti-A antibody in its plasma.

Group AB
Blood has both A and B antigens on red cells but neither anti-A antibody nor anti B antibody in its plasma. AB blood cannot cause the clumping of red cells of any other groups, and therefore persons with AB blood are called universal recipients.

Group O
Blood has neither A nor B antigens on red cells, and both anti-A antibody and
anti-B antibody in the plasma. Group O blood cannot be clumped by any human
blood, and therefore persons with Group O are called universal donors.

What is the Rh factor?

Most people also have an inherited condition of the red blood cells known as the Rh factor, or antigen D. When the D antigen is present, a person's blood type is designated Rh positive. When antigen D is missing, the blood type is classified Rh negative. In general, Rh negative blood is given to Rh negative patients and Rh positive blood to Rh positive patients.

How can I tell what blood type I can receive?

This chart shows what blood types you can receive if you need blood.

IF YOUR TYPE IS

YOU CAN RECEIVE

 

O-

O+

B-

B+

A-

A+

AB-

AB+

AB+

X

X

X

X

X

X

X

X

AB -

X

-

X

-

X

-

X

-

A+

X

X

-

-

X

X

-

-

A-

X

-

-

-

X

-

-

-

B+

X

X

X

X

-

-

-

-

B-

X

-

X

-

-

-

-

-

O+

X

X

-

-

-

-

-

-

O-

X

-

-

-

-

-

-

-

How common are the blood groups in the United States?

The following list shows the percentage of people in the United States with a particular blood type. These percentages may vary in certain sections of the country depending upon the cultural make up of the population.

O Positive 38.4%
A Positive 32.3%
B Positive 9.4%
O Negative 7.7%
A Negative 6.5%
AB Positive 3.2%
B Negative 1.7%
AB Negative .7%

Why are there so many appeals for type O blood?

The Group O donor is called the "universal donor" because their blood can be transfused to people of all blood types. This is why Red Cross is constantly recruiting donors with Group O blood types.

In an emergency, a person may need blood to survive, and if their blood type is not known, type O negative blood is given. In addition, newborns who need blood to survive often need type O negative blood. The Red Cross has a critical need for an adequate supply of type O negative blood to treat community emergencies.

Do blood types differ between ethnic groups?

Yes. For example, about 60 to 70 percent of the Hispanic population represent Type O blood -- the blood type in greatest demand. Only about 45 percent of other ethnic groups are Type O. As our Hispanic population continues to increase, so does the need for Type O blood. Unless we have more Hispanic donors, it will be extremely difficult, if not impossible, to meet this need.

Seasonal shortages of types O and B blood are common because they are in great demand. Many African-Americans have types O and B blood. Nearly 20% of all African-Americans have type B blood, compared to 11% of the Caucasian population.
Blood type, like eye color, is an inherited trait. Some African-Americans have rare blood types that are unique to their ethnic group.

Sickle Cell Disease is a blood disorder found primarily in the African-American community. Patients with Sickle Cell Disease are less likely to have physical reactions to blood donated by other African-American people. An African-American blood type could be the only hope for an individual's survival. The most compatible blood for a transfusion for a critically ill patient is most likely to come from someone with the same ethnic, racial and genetic background as the patient.