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Finding out your blood type is relatively simple. You can:

  • have a test done by your doctor
  • get the information when donating blood
  • take an at-home blood test

Your blood type is comprised of two blood groups: ABO and Rh.

Blood types are based on antigens on the surface of your red blood cells. An antigen is a substance that triggers an immune response by your body against that substance.

ABO blood types group your blood by the presence of specific antigens:

  • Type A has the A antigen
  • Type B has the B antigen
  • Type AB has both the A and B antigen
  • Type O doesn’t have either the A or B antigen

Once your ABO blood type has been determined, it can be further defined by identifying the Rhesus (Rh) factor:

  • Rh-positive. If you have Rh antigens on the surface of your red blood cells, you have Rh-positive blood.
  • Rh-negative. If you don’t have Rh antigens on the surface of your red blood cells, you have Rh-negative blood.

By including the Rh factor, the 8 most prevalent blood types can be identified: A+ or A-, B+ or B-, AB+ or AB-, and O+ or O-.

At your doctor’s office, a clinical laboratory, or a hospital, a phlebotomist (someone trained to draw blood) will use a needle to draw blood from your arm or hand.

That blood will be mixed with antibodies and the reaction will be noted. For example, if your blood cells clump together (agglutinate) when mixed with antibodies against type B blood, you have type A blood.

Next, your blood will be mixed with an anti-Rh serum. If your blood cells respond by clumping together, you have Rh-positive blood.

In at-home blood typing tests, they typically ask that you prick your finger with a lancet and put drops of your blood on a special card.

After putting the blood on the card, you can observe the areas where blood clumps or spreads out, and then match those reactions to an included guide.

Some home testing kits have vials of fluid for your blood, as opposed to a card.

Purchase an at-home blood typing kit here.

One way to find out your blood type is to donate blood.

If you donate to community blood supplies, ask the staff if they’ll be able to tell you your blood type. Many donation centers are able to provide that information.

Typically you won’t get your blood type immediately and may have to wait a few weeks, as blood isn’t commonly tested right away.

About 80 percent of people secrete blood group antigens in other bodily fluids, such as saliva, mucus, and sweat. This group of people is referred to as secretors.

Secretors can have their blood type determined by a saliva or other body fluid test.

Blood typing kits using saliva are available online, but are typically more expensive. Using one of the kits, you’ll first learn whether or not you’re a secretor. If you are, then you’ll be able to determine you ABO blood type.

There are a number of ways you can determine your blood type, including:

  • visiting your doctor
  • going to a hospital or clinical laboratory that tests blood
  • donating blood
  • getting a home testing kit

If you’re in the category of people who secrete blood group antigens in other bodily fluids, you can find out your blood type without having blood drawn.