Why Are Rare Blood Types More Common Than You Think?

Updated on September 18, 2019
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Lela is a Certified Medical Laboratory Scientist (ASCP) with 38 years of experience in the medical industry and blood banking.

Percentage of Blood Types Worldwide Estimate (1):

Average estimate of blood type distribution of the 8 common blood types
Average estimate of blood type distribution of the 8 common blood types | Source

The eight major blood types procedure

The first thing a blood bank technologist will do when typing your blood is to discover the major blood antigens and antibodies in your test sample.

We will mix your red blood cells with two reagents called Anti-A and Anti-B(2):

  1. If only the A test is positive (clumping of the red cells is seen), then you are in Group A
  2. If only the B test is positive, then you are in Group B
  3. If both the A and B test are positive, then you are in Group AB
  4. If neither the A or B test are positive, then you are in Group O (Interesting fact: the O stands for the number zero indicating no reaction is present.)

The next test we will do is for the Rh factor. We use one or two reagents here, the D test, and/or the DC (D control) test. The Rh factor was discovered in Rhesus monkeys, but this genetic marker is not limited to monkeys, it is found in humans also, and is signified by the capitol letter, D.

  1. If the D test is positive and the D control test is negative, you are D+, or what used to be called Rh Positive.
  2. If the D test is negative and the D control test is negative, you are D-, or Rh Negative. A secondary test with 37°C incubation is done to confirm that no D+ cells are present. This is called the "weak D" test.
  3. If both the D and DC are positive, the test must be repeated as some protein is covering and interfering with the D receptors. Wash the cells with normal saline and repeat.

After these two determinations are made, a second technologist must confirm the ABO Rh by duplicate testing if the patient will be getting a transfusion of compatible red blood cells. This is called a group and type confirmation.

What is the rarest blood group and type?

As you can see from the chart above, the "rarest" blood type is AB Negative at 0.6% frequency in the world wide blood type distribution. This is actually not all that rare as there are about 7.5 billion people on the planet.

So, the number of people with AB Negative blood would be an estimated count of roughly four million people!

That's not really "rare". It is called "low frequency" instead.

To get to the really rare types of blood, we have to go a bit further down the antigen typing trail.

But wait! That's not all there is to blood typing and compatibility testing.

Blood Antigen Typing
Blood Antigen Typing | Source

Your blood can be positive or negative for these antigens too!

According to Wikipedia, there are more than 200 minor blood groups in addition to the four major blood groups of A, B, AB, and O; and the Rh D typing.

Before doing compatibility testing for red cell transfusions, a technologist will test your blood with a screening panel of cells that are positive for the unexpected antigens in the Rh, Kell, Duffy, Kidd, Lewis, P, MNS, Lutheran, and other systems.

If your plasma reacts with a cell that is positive for any of these antigens, we must identify the corresponding antibody in your blood.

We cannot give you blood that is positive for any antigen that you have an antibody to.

This will cause a transfusion reaction ranging from mild to severe. It can even cause death.

The antigen screening test is limited to these antigen blood types. If we still cannot identify your rare antibody, then we must do more specialized testing.

The third step in cross-matching blood is to do a donor and recipient compatibility test to make sure the donor blood we choose is not going to cause a reaction in the recipient.

Examples of rare, or special blood types:

Blood Type
Yes, it is special
No, it is not special
O+, O-, A+, A-, B+, B-, AB+, AB-
Rh Negative
Unexpected Antigen +

What is the rarest blood type that includes unexpected antibodies to blood antigens?

This is where we start getting into truly rare blood types.

Some antigens are specific to certain areas of the world's indigenous population. These antigens developed during our genetic evolution. Some populations have the gene for "rare" antigens.

Rumors and superstitions grew up around these "rare" or "golden" blood types. Blood is still thought of as "magic", or "containing the soul", or "alien" in some ways.

All of these notions are simply related to genetic evolution and incompatibility of antigens versus antibodies.

The rarest blood type I have seen in 38 years of transfusion services is the Lutheran A antibody in a patient that needed Lutheran A Negative blood. Unfortunately, 98% of the world's blood is Lutheran A antigen Positive.

We cannot give you blood that is positive for any antigen that you have an antibody to.

This is the "golden rule" of compatibility testing! This is what makes a blood type rare, or golden, or alien. It is simply a question of compatibility and frequency of occurrence.

Why do you think rare blood types are special?

So called rare blood types are definitely not special, or rare, or magical, or alien, or golden. They are, in fact, something that you DO NOT want to have!

  • If you have "rare" blood, we will have a hard time finding compatible blood for you.
  • If you have "golden" blood, we will not be able to find blood for you at all in the event of an emergency when your life is at stake.
  • If you have "alien" blood, the rumors of extra-terrestrial life are true.
  • If you have "magic" blood, we would want you to donate every 6 to 8 weeks so everyone can have some of your blood.
  • If you have "special" blood, we would want you to donate every 6 to 8 weeks so a person with the corresponding antibody will be able to get a life saving transfusion.

Donating blood saves lives!

Blood is the gift of life.
Blood is the gift of life. | Source

Rh Negative blood, and Can an O+, A+, B+, AB+, or Rh- man marry an Rh- woman (insert A, B, or AB, blood group for the woman)?

Note(3): All Rh Positive women will NOT have the Rh Negative dilemma, but may have a milder form of antibody/antigen reactions in their children which do not have anything in common with the Rh Negative dilemma.

The Rh Negative, "rare", "alien", and "superstition" blood rumor, is that Rh Negative women cannot marry (or conceive with) Rh Positive men because it will affect their children.

Their major blood groups (O, A, B, and AB) do not usually cause the severe form of Hemolytic Disease of the Newborn (HDN), while the Rh factor may cause severe reactions.

Rh Negative mothers often get pregnant by Rh Positive fathers. This is a well known and understood condition caused by antigen/antibody incompatibility.

The first Rh (D) positive fetus will "immunize", or "sensitize", the Rh (D) Negative mother. She will develop antibodies, called Anti-D to the D Positive antigens of the fetus.

Note that this is still an antibody/antigen reaction that occurs naturally, and is not from "alien", "magic", or "special" blood types.

The second and subsequent pregnancies of a sensitized mother with an Rh (D) Positive fetus may develop Hemolytic Disease of the Newborn (HDN). This is the Anti- D antibody in the mother that is attacking and destroying the D Positive antigens on the fetal red blood cells.

Rh-immune Globulin to the rescue!

Modern medicine has developed a vaccine of a sort, called Rh-immune Globulin, brand name, RhoGam®, to protect babies from HDN in Rh (D) Negative mothers.

Rh-immune Globulin tricks the Rh (D) Negative mother's immune system into believing it has already produced Anti-D antibodies, so the immune system relaxes and doesn't make her produce her own more powerful Anti-D antibodies.

The baby may or may not be born with HDN in mothers who have had the Rh-immune Globulin injections to protect the fetus.

The injections are not needed if you are an Rh (D) Negative mother and the child's father is verified to also be Rh (D) Negative. In all other cases, it is highly advisable to get the injections to protect the baby.

Can people of different blood types marry? What are the personality traits of the different blood types?

This question comes up extremely frequently! It is second behind the "rare" blood type questions.

There are some pseudo studies of blood types and their differing personalities. None of these studies are scientifically documented and verified. There is no reason to suspect that genetic blood types affect a person's personality and marriage compatibility.

Genetics regulate our blood types, hair color, eye color, nose shapes, skin tones, and a few thousand other things. What you are born with is what you get. The only gene changing you can do is via a new process called Crispr, and I won't cover that here.

See a marriage counselor before getting married if you are concerned about marriage and personality compatibility. Blood types do not determine if you should marry someone or not.

Please take this poll so I can update this article with blood bank news you can use...

Do you now understand rare blood types?

See results

Technical References:

  1. American Red Cross et al, October 11, 2018, Blood Types & Groups Chart | A, B, AB & O | Red Cross Blood Services, American Red Cross website, published by the American Red Cross Blood Services, https://www.redcrossblood.org/donate-blood/how-to-donate/types-of-blood-donations/blood-types.html
  2. Kedrion Biopharma Inc., October 13, 2018, RhoGAM - FAQ, Fort Lee, NJ, Published by ©2018 Kedrion Biopharma Inc, http://www.rhogam.com/faq/
  3. OLYMPUS AMERICA INC., 056EN01 – Package insert updated in December, 2007, Blood Grouping Reagents, Center Valley, PA, published by: Olympus America, Inc.,PDF.

This content is for informational purposes only and does not substitute for formal and individualized diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed medical professional. Do not stop or alter your current course of treatment. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

Questions & Answers

  • When concerning rare blood types, what does Du or D positive test signify?

    The Rh antigen has a new name! It is now the D, or d antigen. D = Rh Positive, and d = Rh Negative. Du = a weak expression of the D antigen, but is seldom used these days.

© 2018 Lela

What would you like to know about "rare" blood?

Submit a Comment
  • Nell Rose profile image

    Nell Rose 

    20 months ago from England

    My other half has a rare blood type, can't remember which though! Interesting stuff! and really useful for anyone needing to know about blood groups.


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