A positive, O negative, AB negative and universal donors…what does it all mean? How does blood type affect us, and what are the important things we need to know? Here are some of the basics.
Although everyone’s blood does the same thing, not all blood is the same. Blood types classify blood, so healthcare providers can determine whether one person’s blood is compatible with another’s.
Blood types are determined by the presence or absence of certain antigens. Antigens are substances in blood that can trigger an immune response if they are foreign to the body. Sometimes antigens can trigger a patient’s immune system to attack blood from a blood transfusion. Because of this, safe blood transfusions depend on careful blood typing and cross-matching. Do you know what blood type is safe for you if you need a transfusion? Blood transfusions and organ transplants depend on donors and recipients having compatible blood types. Blood types include A, B, AB and O.
Also, there is Rh-negative blood vs. Rh-positive blood. If you have the Rh factor protein, your blood type is positive (+), and if you don’t, it’s negative (-). Rh-negative blood is given to Rh-negative patients, and Rh-positive or Rh-negative blood may be given to Rh-positive patients. The rules for plasma are the reverse. It can get kind of confusing. Taking all this information into consideration, there are eight distinct common blood types:
- A positive (A+)
- A negative (A-)
- B positive (B+)
- B negative (B-)
- AB positive (AB+)
- AB negative (AB-)
- O positive (O+)
- O negative (O-)
The most common blood type in the United States is O positive (O+).
The least common blood type in the United States is AB negative (AB-).
Rare Blood Types
There are more than 600 other known antigens, the presence or absence of which creates “rare blood types.” Your blood type is considered rare if you lack antigens that 99% of the people are positive for. If you somehow lack an antigen that 99.99% are positive for, your blood type is extremely rare.
Other blood group systems include the:
- Duffy blood group
- K antigen (or Kell) group
- Lutheran blood group
- Kidd blood group
These blood groups are rare. A general definition of a rare blood type is one that happens at a rate of 1 per 1,000 people or fewer.
One of the world’s rarest blood types is Rh-null. Fewer than 50 people in the world have this blood type. It’s so rare that it’s sometimes called “golden blood.”
How are blood types inherited?
You inherit your blood type the same way you inherit your eye color – from your biological parents. Both the ABO genes and the Rh factors come from your parents. Due to the many possible combinations, you might not have the exact same blood type as your parents.
Which blood types are compatible?
An important part of blood donation is ensuring that someone receiving blood (recipient) has a compatible blood type with someone donating blood (donor). See chart below for details on which types can donate to and receive from others.
How can you find out your blood type?
You can ask your physician. Sometimes they have your blood type listed in your record. Another way to find out, which would be helpful to you and others, is to volunteer to donate blood if you’re eligible.
How does blood type affect pregnancy?
A fetus may inherit its Rh factor (either positive or negative) from either parent. There may be problems if a mother is Rh negative and carrying a fetus with blood that’s Rh positive.
During your first visit to your obstetrician, you’ll take a blood test to determine your blood type and screen for antibodies. If your body reacts to Rh-positive red blood cells, your anti-Rh antibodies can begin to attack the fetus’ red blood cells.
To prevent this from happening, you’ll receive Rh immunoglobulin (RhIg). RhIg is a medicine that blocks antibodies from attacking the fetus’ blood.
Can your blood type change?
Most likely, you will have the same blood type all your life. In rare cases, however, blood types can change. The change usually relates to unique circumstances, such as having a bone marrow transplant or getting certain types of leukemia or infections. Not all of these changes in blood type are permanent.