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I never really paid much attention to blood types… I don’t even know my own! But it was interesting to me how some blood types could be universal donors, while others could not. So I decided to take a look into it and provide my insights on them, as well as a quick explanation on what they actually are.

Why do we even have ‘blood types’? Scientists think that we evolved with different blood types to fight off different types of diseases, and it happened through genetic mutations. It is most widely presumed that a long time ago, people in different parts of the world were subject to different bacteria and viruses; hence, their bodies developed ways to become immune to them. One of these ways was the blood type.

We have four types of blood groups. A, B, AB, and O, and there are two factors that make blood groups different from each other: antigens and antibodies. To make it simpler, I can condense this into a few statements:


  1. There are 2 types of antigens — A and B
  2. Group A has A antigens
  3. Group B has B antigens
  4. Group AB has both antigens
  5. Group O has neither of the antigens


  1. There are 2 types of antibodies — anti-A and anti-B
  2. Group A has anti-B antibodies
  3. Group B has anti-A antibodies
  4. Group AB has neither of the antibodies
  5. Group O has both antibodies.

But have you ever seen a + or – sign at the end of the blood grouping? That denotes the Rh factor in the blood. Rh is a another antigen; but unlike A and B antigens, it is a protein. A + means Rh is present, and a – means it is not.

As you may have already guessed by now, A and B antigens are sugars that make your immune system to respond to bacteria, etc. and antibodies are what make blood types reject select other blood types. To put it simply, the body creates antibodies for antigens that you do not have.

This is why we can never mix blood types that do not have the same antigens. (Doctors learned that the hard way.)

If this happens, the antibodies in your blood will destroy the new blood cells. This is called an ABO Incompatibility Reaction. For example, if a type B person is given type A blood, the anti-A antigens in the B blood will destroy the A blood. So we need two other lists that expands on our statements above:

Receiving Blood

  1. Type A (anti-B) can receive blood from A and O types
  2. Type B (anti-A) can receive blood from B and O types
  3. Type O (anti-B and anti-A) can only receive blood from O types
  4. Type AB (no antibodies) is the Universal recipient. I can receive blood from all types.

Giving Blood

  1. Type A (A antigen) can give blood to type A and type O
  2. Type B (B antigen) can give blood to type B and type O
  3. Type O (no antigens) is the Universal Donor. It can give blood to all types.
  4. Type AB (A and B antigens) can only give blood to type AB.

Two charts are not needed to understand both processes (because they are just from two perspectives of the same occurrence). But it does make it easier!

Just to reiterate, somebody can receive blood that has the same or no antigens as them. That will ensure that there are also the same antibodies. somebody can give blood if they have the same antigens as the other type (to ensure that the antibodies do not clash).

If two types of blood are mixed, the blood clumps (agglutinates). The person also shows many symptoms: fever, nausea, pain, aches, etc. The blood clots can clog arteries, which in turn cuts off the blood supply to vital organs. Destroyed blood cells can also damage the kidney. So, if not treated immediately, an ABO Incompatibility reaction can lead to death.

And that’s why it is so important to learn about blood types! Of course, doctors take care of this problem, but it is important to be aware of your own health and safety.

Remember, your knowledge of blood types will never be in vein!


healthline – ABO Incompatibility Reaction

Aggarwal, S. K. Learning Elementary Biology for Class 8 (for ICSE Schools). Goyal Brothers Prakashan, 2015.

Check Out

Canadian Blood Services (for Canadian statistics on blood types)

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