What is the least common blood type?

The Least Common Blood Type

The AB-negative (AB-) blood type is the least common blood type in the general population, occurring in only about 0.06% of people. 1

Blood Type Distribution

• The ABO blood group system combined with the Rhesus (Rh) factor creates eight main blood types: A+, A-, B+, B-, AB+, AB-, O+, and O- 2
• Blood type distribution varies by population and ethnic ancestry, with some blood types being more common in certain regions 1
• In general population studies, the AB blood group is consistently the least common ABO type, representing only about 5-8% of people 3, 4
• When combined with Rh-negative status (which occurs in approximately 5.5% of people), AB-negative becomes extremely rare 3

Blood Type Rarity Hierarchy

• AB-negative is the rarest of the eight main blood types 1
• B-negative is the second rarest blood type 4
• Other rare blood types include:
  • The Bombay blood group (Oh phenotype), which is extremely rare at 0.004% prevalence 3
  • The p phenotype, which is defined by the absence of high-prevalence antigens and is associated with difficulties finding compatible blood for transfusion 5

Clinical Significance of Rare Blood Types

• Individuals with rare blood types may face challenges finding compatible blood for transfusion in emergency situations 5
• For AB-negative individuals specifically:
  • They can only receive AB-negative or other Rh-negative blood types 2
  • They can donate plasma to all blood types (universal plasma donor) but their red blood cells can only be given to other AB-negative recipients 2
• Blood banks must maintain inventories of rare blood types or have access to rare donor registries for patients with uncommon blood types 5

Blood Type Conversion Research

• Research is ongoing to develop enzymatic methods to convert A, B, and AB blood types to O type (universal donor) 6
• This conversion would be particularly valuable for rare blood types like AB-negative, potentially increasing the available blood supply for emergency transfusions 6

Geographic Variations

• Blood type distribution shows regional differences:
  • In some South Indian populations, O is the most common blood group (38.75%), followed by B (32.69%), A (18.85%), and AB (5.27%) 3
  • In certain North Indian regions, B is the most common blood group 3
  • The prevalence of Rh-negative blood is approximately 5.5% across different Indian populations 3, 4

Understanding the distribution of blood types is essential for blood bank inventory management and transfusion services, particularly for ensuring availability of rare types like AB-negative for patients who need them 4.