Which Blood Groups Are Rare? Complete Comparison

If you have type O blood, you are not rare. About 45% of people in the US share your blood type. But if you have AB negative, you are in a much smaller group. Only about 0.6% of US donors have it. Blood type rarity depends on where you live and your ancestry. The rarest blood type overall is AB negative, followed by B negative and A negative. But the truly rarest blood type in the world is Rh-null, sometimes called “golden blood.” Fewer than 50 people on Earth are known to have it. This article compares which blood groups are rare, why they matter, and what the evidence actually shows.

What Makes a Blood Type Rare?

Blood types are determined by antigens. These are markers on the surface of your red blood cells. The two most important systems are the ABO system and the Rh system. The ABO system gives you type A, B, AB, or O. The Rh system tells you if you are positive or negative. That gives us eight common blood types.

Rarity happens when a combination of antigens is uncommon in a population. For example, AB negative is rare because only about 3-4% of people have type AB blood, and only about 15% of people are Rh negative. Multiply those numbers together and you get a very small percentage.

But rarity goes deeper than ABO and Rh. There are over 300 other blood group systems. Some people lack antigens that almost everyone else has. That is where truly rare blood types like Rh-null or Duffy-negative come from. The American Red Cross tracks these through the International Rare Donor Registry.

Which Blood Groups Are Rare in the United States?

The data from blood donation organizations is clear. Here is the breakdown of blood type frequencies among US donors according to the American Red Cross:

• O positive: 37.4% — most common
• O negative: 6.6% — universal donor but not rare
• A positive: 35.7% — very common
• A negative: 6.3% — less common but not rare
• B positive: 8.5% — uncommon but not rare
• B negative: 1.5% — moderately rare
• AB positive: 3.4% — uncommon
• AB negative: 0.6% — rarest of the eight standard types

AB negative is the rarest standard blood type in the US. Only about 1 in 167 people have it. B negative is the second rarest, and A negative is third. If you have any negative blood type, you are already in a minority. Only about 15% of people are Rh negative overall.

These numbers shift depending on ethnicity. For example, B positive is more common in Asian populations. AB negative is extremely rare in people of African or Asian descent. The numbers above represent averages across all US donors.

What Is the Rarest Blood Type in the World?

The rarest blood type in the world is not AB negative. It is Rh-null. This blood type has no Rh antigens at all. Almost everyone has some Rh antigens. People with Rh-null are missing all of them. As of 2026, fewer than 50 people worldwide have been identified with this blood type. That is why it is called “golden blood.”

Rh-null is incredibly valuable to medicine. Because it lacks all Rh antigens, it can be given to almost anyone with a rare Rh blood type. The National Institutes of Health and other agencies track these donors carefully. If you have Rh-null, you are encouraged to donate regularly because your blood is irreplaceable for certain patients.

Other truly rare blood types include Duffy-negative, which is common in people of African ancestry but rare in other populations. There is also the Bombay blood type, which is most common in India. People with Bombay blood can only receive blood from other Bombay donors. The American Rare Donor Program lists over 200 rare blood types, but Rh-null remains the rarest known.

How Blood Type Rarity Affects Blood Donation and Transfusions

Blood type rarity matters most in emergencies. If you have a common blood type like O positive, hospitals almost always have your blood in stock. If you have AB negative, supplies are limited. Hospitals may need to request it from regional blood centers.

For people with truly rare blood types, the situation is more serious. If you have Rh-null or Bombay blood, a standard blood transfusion could kill you. Your immune system would attack the donor blood because it contains antigens your body does not recognize. That is why rare donor registries exist. The American Red Cross and the National Institutes of Health maintain databases of rare blood donors. They can ship blood across the country or even internationally when a patient needs it.

Blood type rarity also affects pregnancy. If an Rh-negative mother carries an Rh-positive baby, her body can produce antibodies that attack the baby’s blood. This is called Rh incompatibility. It is preventable with a shot called RhoGAM. But for women with very rare blood types, finding compatible blood for transfusion during pregnancy can be difficult. The CDC and the American College of Obstetricians and Gynecologists recommend early blood type testing for all pregnant women.

Does Blood Type Rarity Affect Your Health?

There is a lot of misinformation online about blood types and health. Some websites claim that rare blood types make you more prone to certain diseases. The evidence does not support most of these claims.

Research published in the journal Blood and other peer-reviewed sources has found some associations. For example, people with type O blood have a slightly lower risk of blood clots. People with type A blood have a slightly higher risk of stomach cancer. But these are small statistical differences. They are not strong enough to change how you should live your life.

There is no credible evidence that rare blood types cause personality traits, determine your ideal diet, or predict your athletic ability. The “blood type diet” is not supported by clinical research. The American Heart Association and the National Institutes of Health do not recommend any health changes based on blood type alone.

The one area where blood type clearly matters is transfusion and pregnancy. If you have a rare blood type, you should know it. You may want to donate blood regularly to help others with your type. But do not worry that your rare blood type is a hidden health risk. The evidence does not show that.

How to Find Out Your Blood Type

Many people do not know their blood type. If you have never donated blood or had a blood test, you may not know. Finding out is simple.

The easiest way is to donate blood. The American Red Cross or your local blood bank will tell you your type for free. They also check for rare types as part of their screening. If you have a rare blood type, they may contact you about becoming a regular donor.

You can also ask your doctor for a blood type test. This is a standard lab test and is usually covered by insurance. At-home blood type kits are available online, but they are not always accurate. The FDA does not regulate them as medical devices. If you want a definitive answer, get tested by a medical professional.

If you are pregnant, your blood type will be tested as part of routine prenatal care. This is important for Rh incompatibility screening. If you are Rh-negative, your doctor will monitor you and may recommend RhoGAM.