“Your blood type is determined by which types of sugars or antigens are decorating the surface of the red blood cell,”
The antigens are determined from a combination of your parents’ genes.
Whether your blood type is A, B, AB or O depends on whether you have or don’t have certain antigens, A or B, on your red cells:
- All blood has a base of O antigen
- Type A blood has the A antigen on red cells
- Type B blood has B antigen on red cells
- Type AB blood has both A and B antigens on red cells
- O blood type has neither A nor B antigen on red cells
“O is the most common and basic blood type, followed by A, then B, and finally AB,” Dr. Nance said.
The Rhesus factor, or Rh “decoration,” is what is referred to as the positive or negative. Most Americans are Rh-positive. Those who are O negative are considered universal donors, meaning anyone can receive type O negative blood.
Methods to Identify Yours
1. Clinical test
One of the easiest and most effective ways to determine blood type is to have your doctor perform a test. A professional will draw blood and then perform two tests on the blood sample: forward typing and reverse typing.
During forward typing, the blood sample is mixed with antibodies against type A and B blood. Based on whether the blood cells stick together when mixed with the antibodies, your blood type can be determined from there. If your blood cells stick together when mixed with antibodies against type B blood, you have type B blood. If your blood cells stick together when mixed with antibodies against type A blood, you have type A blood
To confirm the result, the next step is reverse typing, meaning the blood sample without red blood cells -- called a serum -- is mixed with type A and type B blood cells. Type A blood will have antibodies against Type B blood in the sample and type B blood will have antibodies against Type A blood. Type O blood will contain antibodies against Type A and Type B. So, if sticking occurs when the serum is mixed with type B blood cells, you have type A blood, and if sticking occurs when the serum is mixed with type A blood cells, you have type B blood.
2. Donate blood
This is an easy -- and free -- way to determine blood type, but results are not immediate.
If you donate to a blood drive, you can simply ask the staff about your blood type. Blood usually is not tested right away, so it may take up to a few weeks to get results.
3. At-home blood test
At-home tests are relatively straightforward. You will usually start by wiping your finger with an alcohol wipe and then be required to prick your finger with a disposable lancet to draw blood. Then, you will wipe blood on the provided card. Depending on how the blood dries, clumps or spreads, you will be able to compare your blood stain to a results card. Within minutes, you'll be able to determine which blood type you are.