What Are the 3 Rarest Blood Types?

Medically Reviewed on 3/2/2022

What does blood type mean?

Blood type determines who you can donate blood to and who you can receive it from.
Blood type determines who you can donate blood to and who you can receive it from.

You must have heard about the terms “blood group” or “blood type.” If you ever have undergone surgery or been admitted to a hospital for medical conditions, your doctor might have examined your blood for various parameters, such as blood counts and blood type. Your blood contains various cells and the liquid portion is called the plasma. The red blood cells or RBCs present in the blood carry certain molecules, called antigens, on their surface that determine what blood group you have. The antigens depend on the genes you inherit from your parents. These antigens may be grouped in various categories to form a system for blood typing called the ABO system. Based on this classification, your blood group maybe

  • A: This type of blood group means the RBCs have the antigen called antigen A on their surface. Apart from the ABO antigens, there is another important antigen on the RBC surface called the Rh antigen. If a person with blood group A bears Rh antigen on their RBCs, the blood group is called A+ (A positive). Likewise, if the Rh antigen is absent the person will be A- (A negative).
  • B: People with the B antigen on the RBC surface have blood group B. This can also be either blood group B+ or B- based upon the Rh antigen status.
  • O: Blood group O means that both antigens A and B are absent from the RBC surface. Blood group O can be O- (O negative) or O+ (O positive) depending upon the absence or presence of the Rh antigen on the surface of the RBCs.
  • AB: Some people may have both the antigens, A and B, on the surface of the RBCs. When both antigens are present, the blood group is called the AB blood type. This may also be AB- or AB+ depending on the absence or presence of the Rh antigen on the surface of the RBCs.

The table below includes various blood types.

Table 1. Blood Types

A negative (A-) A positive (A+)
B negative (B-) B positive (B+)
AB negative (AB-) AB positive (AB+)
O negative (O-) O positive (O+)

What are the 3 rarest blood types?

The blood types vary depending on the genetic makeup of an individual. Since there are differences in the distribution of genes in different parts of the world, the rarest and most common blood groups also vary in different populations across the globe. The rarest blood type in the United States is

  • the AB- (AB negative) blood type, which is seen in just 0.6 percent of people followed by
  • B- (found in 1.5 percent of the United States population) and
  • AB+ (present in just 3.4 percent of people in the United States).

Table 2. The Various Blood Types and Their Prevalence in the United States

Blood type

Prevalence in the United States (Percentage

of the United States population)

A negative (A-) 6.3%
A positive (A+) 35.7%
B negative (B-) 1.5%
B positive (B+) 8.5%
AB negative (AB-) 0.6% (Rarest)
AB positive (AB+) 3.4%
O negative (O-) 6.6%
O positive (O+) 37.4%


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What is the importance of blood type?

Your blood group varies depending on the tiny molecules called blood group antigens that are present on the surface of your red blood cells or RBCs. The antigens depend on the genes you inherit from your parents. These antigens also determine the presence of certain antibodies against blood group antigens in your blood. Thus, a person with blood group A will not have antibodies against the A antigen in their blood. Similarly, a person with AB type of blood will not have antibodies to both blood group antigens A and B. The presence of the antibodies is responsible for the blood transfusion reactions that occur when incompatible blood is transfused into a person. Your blood group determines the blood type you can receive and who you can donate your blood too.

Table 3. Blood Type Compatibility for Transfusion

Blood type Can donate blood to people with these blood groups Can receive blood from people with these blood groups
A negative (A-) A-, A+, AB-, AB+ A-, O-
A positive (A+) A+, AB+ A+, A-, O+, O-
B negative (B-) B-, B+, AB-, AB+ B-, O-
B positive (B+) B+, AB+ B+, B-, O+, O-
AB negative (AB-) AB-, AB+ AB-, A-, B-, O-
AB positive (AB+) AB+ All Blood Types
O negative (O-) All Blood Types O-
O positive (O+) O+, A+, B+, AB+ O+, O-

It has also been observed that people who have certain blood types are prone to certain maladies. It has been observed that people with blood group A are most prone to throw clots and have heart disease. <i>H pylori</i> infection is associated most with people who have O type blood. People with B type blood are most susceptible to TB and <i>E coli</i> infections. These associations are mostly due to a specific subset of the cell proteins present along with the blood group antigens.

How does EldonCard determine blood type?

EldonCard is a newly developed patented test that determines your blood group, which can be used anywhere. It is the cheapest approach to get the most accurate results rapidly within a few minutes without the need for conventional laboratory testing and skilled technicians.

  • The EldonCard blood type test kit uses the basic forward antibody technique of blood hematology for quick and simple determination of your blood type.
  • The most common blood types are A, AB, B, or O, which are determined by the presence of respective antigens (specific proteins present over the red blood cells).

The presence of either of the antigens and special factors on the red blood cells known as the rhesus (Rh) factor determine the blood type. If the Rh factor is absent, then your blood type is Rh-negative, and if it is present, your blood type is Rh-positive.

EldonCard has four small circles, each incorporated with different antibodies.

  • First circle: Named Anti-A and contains antibodies A
  • Second circle: Named Anti-B and contains antibodies B
  • Third circle: Named Anti-D and contains Rh antibodies
  • Fourth circle: Control

When your blood is added to each of these sections, the antigens in your body react with antibodies on the EldonCard to form blood clots. Just by looking at the sections where the blood clots, you can easily determine your blood type.

If clots are seen in the fourth circle (control), it determines that the test is faulty, and you have to get blood grouping done by professionals in a laboratory.

EldonCard summary

  • Correct blood grouping is obtained by comparing blood sample coagulation findings on pretreatment areas of the blood typing test card to a graphic picture chart.
  • The picture chart contains images that show how and where blood clots form for a particular blood type.
  • To create a permanent record, the test card should be filled out with personal identity information and laminated with the accompanying plastic sheet.


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How to read the EldonCard

EldonCard is a small card that contains antibodies incorporated in the circles.

Reading blood clots in the circles will determine your blood group as follows:

  • A positive:
    • A positive means you have antigens A and rhesus (Rh) factor in your blood.
    • Blood clots are seen in the first and third circles in the EldonCard.
  • A negative:
    • A person with A negative blood has antigen A but no Rh factor in the blood.
    • Blood clots are seen only in the first circle on the EldonCard.
  • B positive:
    • The blood contains both antigen B and Rh factors.
    • Blood clots are seen in second and third circles on the EldonCard.
  • B negative:
    • The blood contains antigen B but no Rh factor.
    • The EldonCard shows blood clots only in the second circle.
  • AB positive:
    • AB-positive blood contains both types of antigens A and B, as well as the Rh factor.
    • Blood clots are seen in the first, second, and third circles on the EldonCard.
  • AB negative:
    • This blood type contains both A and B antigens, but the Rh factor is absent.
    • Blood clots are seen in the first and second circles on the EldonCard.
  • O positive:
    • A person with O-positive blood does not have the antigen A or B in the body, but the Rh factor is present.
    • The EldonCard shows blood clots only in the third circle.
  • O negative:
    • An O-negative type of blood does not contain any antigens in the blood.
    • Antigens A and B and Rh factor are absent.
    • The EldonCard will not trigger any blood clots to develop.

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What are the advantages and disadvantages of EldonCard?

Here are the advantages and disadvantages of EldonCard blood tests:


  • EldonCard is easily accessible and can be used anywhere; it is user-friendly and can be used by anyone but requires some caution.
  • It is a secure test in most cases.
  • It can be used to determine the blood group instantly in emergencies such as:
    • Traumatic situations where the person needs an immediate blood transfusion
    • Bedside blood grouping of a person without the hassle of waiting for a lab report
    • Determination of the presence of rhesus factor in a pregnant woman
    • Testing for blood groups in schools and organizations


  • EldonCard does not have any serious disadvantages, and it is almost 99 percent accurate.
  • Only very rare blood group types cannot be determined by the EldonCard.
  • The blood grouping test needs a conventional type of testing by professions only if blood clots are seen in the fourth circle (control).
  • Test kits should be used within 24 hours once exposed to the air.
  • These kits do come with an expiration date from the date of manufacture and should be kept at 98.6°F (37°C) for accurate results.
  • This testing requires pricking the finger for the collection of blood, so it should be done by adults to prevent any unwanted accidents.

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Medically Reviewed on 3/2/2022
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