The Blood Matters Blog ·

Can My Blood Type Change?

While it's highly likely that you will have the same blood type throughout your life, there are a few occurrences that could lead to a change.


Do you know your blood type? Are you sure?

You might be surprised to learn that there are actually multiple instances in which a person’s blood type can change. These occurrences are very rare and are typically the result of a health episode or medical procedure, but they do happen. Prepare to marvel at the human body’s remarkable adaptability.

Way No. 1: Bone Marrow Transplant

One of the most well-documented instances of blood type change occurs after a bone marrow transplant. The bone marrow is responsible for producing red blood cells, white blood cells and platelets, and in certain medical conditions like leukemia, the patient’s diseased bone marrow can be replaced with healthy donor marrow. If the patient and donor have different blood types, a successful bone marrow transplantation leads to a shift toward the donor’s blood type.

Way No. 2: Blood transfusion

It’s also possible for a person who experiences significant blood loss to temporarily manifest a different blood type if they are transfused with a large volume of blood. For example, an AB patient may receive enough O blood units during a transfusion that nearly all of their red cells type as group O. Within a few months, the patient’s bone marrow should naturally replace the transfused blood with his or her original blood type.

Way No. 3: Bacterial Infection

A highly unusual occurrence of blood type change within A groups happens when a bacterial infection in the intestines produces an enzyme that alters the A blood group molecule to closely resemble the B molecule. Known as the “acquired B phenomenon,” this usually affects patients battling colon cancer, bowel obstruction or sepsis.

Fortunately, if you have had a transplant, transfusion, or bacterial infection and have concerns about how this might affect your blood type, our lab professionals here at OBI can quickly identify your blood type during its typical testing and blood donation processing.

Additionally, if you need a blood transfusion, blood bank professionals are required to conduct safety and compatibility tests to ensure that you receive the correct blood. If a hospital has difficulty verifying a patient’s blood type, our reference lab is ready to help out.