Which Blood Type Is the Rarest Globally?

Searching online for the rarest blood type can leave you with more confusion than clarity. In brief, AB negative is the scarcest among the eight primary blood types. The American Red Cross reports that fewer than 1% of U.S. donors have AB negative blood. Globally, AB negative remains rare, with its prevalence ranging from 0.06% to 3% depending on the country. In the United States, only 0.6% of the population possesses this blood type.

However, the reality is that numerous other blood types are even rarer than AB negative, and scientists may still uncover new, even more uncommon ones in the future.

Before exploring the rarest blood types, let's first understand the basic composition of blood. Every individual's blood, irrespective of type, consists of plasma. Within this plasma, the following elements are suspended:

The surface of red blood cells features proteins and sugars known as antigens. These act as identifiers for each cell type. The four primary antigens define the four main blood groups: A, B, AB, and O.

Blood type A carries the A antigen, type B has the B antigen, and type AB contains both A and B antigens. In contrast, type O lacks both A and B antigens. These ABO blood types are further categorized as Rh positive or Rh negative. Rh, derived from the Rhesus protein, is another marker found on red blood cells. Individuals with this Rh factor are Rh positive, while those without it are Rh negative.

The positive or negative Rh factor divides the four primary blood groups into eight distinct types. According to the Stanford Blood Center, the U.S. population distribution is as follows:

For those curious about blood type distributions in other nations, BabyMed.com offers a detailed chart. Blood type is inherited, so certain countries may have higher concentrations of specific blood types based on their ethnic demographics.

Understanding your blood type is crucial, as it determines which blood you can safely receive during a transfusion. Receiving an incompatible blood type can trigger a dangerous immune reaction. Individuals with AB positive blood are known as "universal recipients", able to accept blood from any type, though they can only donate to others with AB positive blood. Conversely, those with O negative blood are termed "universal donors", as their blood is compatible with all types, though they can only receive O negative blood. O positive donors can give to other positive blood types, such as A positive or AB positive, which covers approximately 80% of the U.S. population, making O blood highly sought after.

Individuals with rare blood types often encounter difficulties during medical emergencies, as finding matching donors can be a significant challenge.

The Rarest Blood Types

Some individuals may lack Rh antigens entirely, resulting in a blood type known as Rhnull. This type was first identified around 50 years ago in an Aboriginal Australian and remains exceptionally rare, with fewer than 50 individuals documented to possess Rhnull blood.

Rhnull is often called "golden blood" due to its immense value. It is considered a universal blood type for those with rare Rh system blood types, making it lifesaving in emergencies. However, individuals with Rhnull blood can only receive donations from other Rhnull donors.

Other blood types are equally rare, if not rarer, than Rhnull. As of 2022, the International Society of Blood Transfusion, an organization dedicated to advancing transfusion science, recognizes 44 blood group systems encompassing 354 red cell antigens.

These figures are constantly evolving, with new antigens being discovered and added to blood group systems, while others may become obsolete as new research emerges. This makes it nearly impossible to definitively identify the rarest blood type in existence.