Why a person with type O blood Cannot receive a transfusion of type A blood?

O negative blood is missing both the A antigen and the B antigen and does not contain the protein for Rh positive blood. This means that it’s missing those things that could cause a bad reaction during a blood transfusion and can be given to any blood type. But this also means that people with O negative blood can only receive O negative blood.

What does this mean for you if you have O negative blood?
Become a blood donor!  If you have O negative blood, you can only receive O negative blood, so you want to help ensure that there’s always a good supply on the shelves. If you’re scheduled for a surgical procedure, you can always donate your own blood in advance and be given that during the procedure. But what about an unexpected medical emergency? That’s when O negative donors save lives!

Interested in finding out what blood type you are?  
If you don’t know you’re blood type, the blood center will test your blood when you donate and let you know your blood type. 

A blood transfusion is the transfer of blood or a blood component from one healthy person (a donor) to a sick person (a recipient). Transfusions are given to increase the blood's ability to carry oxygen, restore the amount of blood in the body (blood volume), and correct clotting problems.

In the United States, about 21 million blood transfusions are given every year. Typical transfusion recipients include

  • People who have been injured

  • People undergoing surgery

  • People receiving treatment for cancers (such as leukemia Overview of Leukemia Leukemias are cancers of white blood cells or of cells that develop into white blood cells. White blood cells develop from stem cells in the bone marrow. Sometimes the development goes awry... read more )

  • People receiving treatment for other diseases (such as the blood diseases sickle cell disease Sickle Cell Disease Sickle cell disease is an inherited genetic abnormality of hemoglobin (the oxygen-carrying protein found in red blood cells) characterized by sickle (crescent)-shaped red blood cells and chronic... read more

    Why a person with type O blood Cannot receive a transfusion of type A blood?
    and thalassemia Thalassemias Thalassemias are a group of inherited disorders resulting from an imbalance in the production of one of the four chains of amino acids that make up hemoglobin (the oxygen-carrying protein found... read more )

In the United States, the Food and Drug Administration (FDA) strictly regulates the collection, transportation, and storage of blood and its components. These regulations were developed to protect both the donor and the recipient. Additional standards are upheld by many state and local health authorities, as well as by organizations such as the American Red Cross (see Eligibility Requirements) and the AABB (formerly, the American Association of Blood Banks). Because of these regulations, giving blood and receiving blood are very safe.

However, transfusions still pose risks for the recipient, such as allergic reactions Overview of Allergic Reactions Allergic reactions (hypersensitivity reactions) are inappropriate responses of the immune system to a normally harmless substance. Usually, allergies cause sneezing, watery and itchy eyes, a... read more

Why a person with type O blood Cannot receive a transfusion of type A blood?
, fever and chills, excess blood volume, and bacterial and viral infections. Even though the chance of contracting AIDS, hepatitis, or other infections from transfusions is remote, doctors are well aware of these risks and order transfusions only when there is no alternative. Before ordering a transfusion (except in an emergency), doctors explain the risks of transfusion to people and ask them to sign a document affirming that they understand the risks and giving their consent for transfusion (called informed consent Informed Consent Before performing any invasive test or providing medical treatment, doctors must obtain permission from a competent patient in a manner that is informed and voluntary. The process is known as... read more ).

Rarely, some donors may also develop side effects following donation, including giddiness, low blood pressure, nausea, and tingling/numbness or bruising at the site of needle insertion for the blood draw.

Blood typing

People have different blood types. Blood type is determined by whether certain antigens (complex sugar or protein molecules that can trigger an immune response) are present on the surface of red blood cells. Blood cell antigens include blood group antigens A and B and Rh factor.

The four main blood types are A, B, AB, and O (distribution in general population)

  • A: Antigen A (but not B) is present. (40%)

  • B: Antigen B (but not A) is present. (10%)

  • AB: Antigens A and B are present. (5%)

  • O: Neither antigen A nor B is present. (45%)

Also, blood may be Rh-positive (Rh factor is present on the surface of the red blood cells, 85% of people) or Rh-negative (Rh factor is absent, 15% of people).

Normally, if people lack an A and/or a B antigen, they have naturally occurring antibodies against the antigen or antigens that they lack. For example, people with blood type A have naturally occurring anti-B antibody, and people with blood type O (who lack both A and B antigens) have naturally occurring anti-A and anti-B antibodies. In addition to A and B antigens, there are several other blood group antigens also present on red blood cells. However, people do not have naturally occurring antibodies against these antigens. Such antibodies develop only if people are exposed to these antigens by transfusion.

Some blood types are far more common than others. In the United States, the most common blood types in whites are O-positive (37%) and A-positive (33%), followed by B-positive (9%), O-negative (8%), A-negative (7%), AB-positive (3%), B-negative (2%), and AB-negative (1%).

Compatible Blood Types

Why a person with type O blood Cannot receive a transfusion of type A blood?

A blood transfusion is safest when the blood type of the transfused blood matches the recipient's blood type and Rh status (in other words, the blood types are compatible). Therefore, before a transfusion, blood banks do a test called a type and cross-match on the donor's and the recipient's blood. This test minimizes the chance of a dangerous or possibly fatal reaction.

In addition, the recipient's blood is checked for certain antibodies to red blood cells. Such antibodies can cause a reaction to transfused blood.

However, in an emergency, anyone can receive type O red blood cells. Thus, people with type O blood are known as universal donors. People with type AB blood can receive red blood cells from a donor of any blood type and are known as universal recipients.

Recipients whose blood is Rh-negative must receive blood from Rh-negative donors (except in life-threatening emergencies), but recipients whose blood is Rh-positive may receive Rh-positive or Rh-negative blood.

More Information

The following are some English-language resources that may be useful. Please note that THE MANUAL is not responsible for the content of these resources.

    • AABB: Association for the Advancement of Blood and Biotherapies: Information for Donors and Patients: Provides information for patients and blood donors about blood donation safety and procedures and answers frequently asked questions

    • American Red Cross Eligibility Criteria: Alphabetical: Provides information regarding eligibility to donate blood and blood products

      Can a person with blood type O accept blood type A?

      Type O-positive blood can be transfused to any positive blood type: A-positive, B-positive, AB-positive, and of course other O-positives. Patients with O-positive blood can receive blood transfusions from other O-positives or O-negative donors. The ideal donation types for O+ donors are whole blood or Power Red.

      What happens if Type O receives type A blood?

      If a patient receives a blood type that is incompatible, antibodies that the patient already has in his or her blood will attack the donor red blood cells and destroy them.

      Why can't type O blood receive type AB blood?

      Type AB blood has both A and B antigens, and type O blood has neither A nor B antigens. Your immune system will produce antibodies against any blood antigens you don't have in your own blood.

      Who can type O receive a blood transfusion from?

      Those with O positive blood can only receive transfusions from O positive or O negative blood types.