🩸 What Is the Rarest Blood Type? All 8 Types Ranked

📊 All 8 Blood Types Ranked

🗺️ Regional Variations

Blood type distribution varies dramatically by region. Type B is most common in Central and East Asia (~25%), while Type O dominates in Central and South America (~70% in some indigenous populations). Rh-negative blood is most frequent in the Basque region of Spain/France (~30%), but nearly absent in East Asian populations (<1%).

🌍 Why the Percentages Shift From Country to Country

The usual eight-type ranking follows standard US estimates, which Stanford Blood Center publishes citing the AABB Technical Manual, 18th edition: 37.4% O positive at the top, 0.6% AB negative at the bottom. They reflect one country's mix of ancestries, so other countries report different numbers.

NHS Blood and Transplant, for example, reports its donors as 36% O positive, 28% A positive, 14% O negative and 1% AB negative, with 77% RhD positive overall (figures accurate at February 2026). The O-negative share is more than double the US estimate, and the RhD-negative share is about half again as large. Part of that gap is ancestry, and part is recruitment: O negative is the type hospitals reach for in emergencies, so blood services work hard to keep those donors on the register.

🧪 What Transfusion Medicine Calls Rare

ABO and Rh are two of the 48 blood group systems recognised by the International Society of Blood Transfusion (ISBT), whose registry currently lists 398 red-cell antigens. Blood banks use a stricter test: NHS Blood and Transplant puts the UK definition at a type occurring in 1 in 1,000 of the population or less, which usually means lacking an antigen almost everyone carries, or several common ones at once. Rhnull and the Bombay phenotype clear that bar easily. AB negative, at about 1 in 167, is the rarest of the eight common types but is still roughly six times too common to qualify.

That threshold is the reason for the International Rare Donor Panel. It was conceived in 1965 under a joint WHO and ISBT initiative and is maintained by the Red Cell Reference department of the International Blood Group Reference Laboratory in Bristol. It holds details of rare donors from 27 contributing countries, plus frozen unit inventories from frozen blood banks around the world: a last resort for types no single national service could stock alone.

Some of the blood that services struggle most to supply is not rare by that definition. NHSBT reports that 47% of Black heritage donors have the Ro subtype, against only 3% of regular donors, and that demand for Ro is rising by 10 to 15% every year. The driver is sickle cell disorder, which NHSBT calls the UK's fastest growing genetic disorder: patients on lifelong transfusions need blood matched beyond ABO and Rh, and about 6,500 donations a month are needed for them. Ro is far too common to meet the 1-in-1,000 bar, yet hard to supply: scarcity depends on who needs a type and who donates it, not just on how many people have it.

⚠️ When "Rh Negative" Isn't a Settled Fact

An estimated 0.2% to 1.0% of people of European descent inherit RHD genes that code for a serologic weak D phenotype. Their red cells carry the D antigen, but too faintly for some tests to call clearly, so the same person can be recorded Rh positive at one hospital and Rh negative at another. About 95% of central Europeans with a serologic weak D result carry weak D type 1, 2 or 3, and these can be managed safely as RhD positive.

That was the conclusion of a work group convened by the AABB and the College of American Pathologists, published in Transfusion in 2015. It recommended RHD genotyping when RhD typing results are discordant, or when a serologic weak D is found in a female of childbearing potential. The group estimated that as many as 24,700 antepartum and postpartum injections of Rh immune globulin are given each year in the United States to such patients, doses genotyping could avoid. The same test protects in the other direction: women whose weak D turns out to be a different RHD variant should still receive conventional Rh immune globulin prophylaxis.

A home typing card will not pick up any of this. Before a transfusion you are typed again from a fresh sample and crossmatched, whatever an old result says. Antigens beyond ABO and Rh are usually tested only when an antibody screen is positive or a patient starts regular transfusions, which is why most people with genuinely rare blood find out only when something forces the question.