The Basics on Blood: What’s Your Type and Can It Change?

Blood samples kept in test tubes for screening in the lab.

Blood typing is important – especially if you plan on receiving a blood transfusion at a hospital, as receiving the wrong blood type can be deadly.

There are four main blood types: O, A, B, and AB. However, there are many subsets of these blood types and rare variations. In the United States 46.6% of people have type O blood, the most common form, followed closely by type A blood with 37.1%.

Your blood type comes from your genes, which means you may have a similar blood type as your parents or your children. The gene is actually located on your ninth chromosome, and it stays with you for life. However, is it possible to override this and change your blood type? I recently received this question on Twitter.

@ThaboKK22: @DrOz Why is it that in the recent 3 years more people are complaining that their blood type has changed?

Before we get into that, let’s start with a little background. What do all these letters mean? No one marks our blood cells with an “A” or “B” with a tiny marker. Our blood type comes from the presence of special sugars (also known as “antigens”) that live on the walls of our blood cells. They exist to let the body know that this particular type of blood belongs to it. (“This cell is mine! See, it has my name on it!”)

Those with type A blood, have a special “A” antigen attached to their blood cells. Those with type B blood have a “B” antigen. Those with type AB blood happen to have both “A” and “B” antigens.

However, those with type O blood don’t have “O” antigens. They actually have no antigens at all! Imagine the “O” to be a big fat zero, for no antigens!

In regard to changing blood type, I’ve heard of this happening, though not frequently. Most times, it’s a matter of confusion; one may get his or her blood tested to surprisingly find out that he or she has type O blood when he or she could have sworn that she had type A blood as a child.

While there have been reports of bone marrow or liver transplants having changed a person’s blood type, a person’s genetics stay consistent. The reported change is most likely due to a testing error. All tests have an error rate, which is why we tend to repeat blood type tests (or type and screens) before major surgeries in lieu of asking what the patient recalls. We have to do it to make sure.

Interestingly, I did find an article in the Telegraph that reveals that scientists have found a way to change a blood type. By using a special bacterial enzyme, they can turn donated type A, B, or AB blood into type O blood in the bag, which happens to be universal donor blood that can be donated to anyone.

This opens up the possibility that germs, viruses, or toxins may have the potential to change one’s blood type within our own bodies.

An article reported on a 4-month-old girl with congenital rubella who had type A blood that eventually switched to type O after weeks of testing. The scientists suspect an enzyme just “ate” the type A antigens, which made this little girl’s blood type appear to be type O. Science and the body never cease to amaze. It’s quite interesting!