Human biology

Blood Types

The eight main blood groups, who can donate to whom, and how common each is in the UK and worldwide.

The ABO and Rh systems

Your blood type is set by antigens — markers on the surface of your red blood cells — and the antibodies in your plasma. Two systems matter most:

  • ABO system: whether your cells carry the A antigen, the B antigen, both (AB) or neither (O).
  • Rh (D) system: whether you also carry the RhD antigen — positive if you do, negative if you don't.

Combining them gives the eight main types (O+, O−, A+, A−, B+, B−, AB+, AB−). Matching matters for transfusions: O− is the "universal donor" for red cells (safe for almost anyone in an emergency), while AB+ is the "universal recipient".

UK population

Approximate share of the UK population (NHS Blood and Transplant).

A-8%
A+30%
AB-1%
AB+2%
B-2%
B+8%
O-13%
O+35%

World population

Broad global estimate — the mix varies widely between populations.

A-2%
A+27%
AB-1%
AB+5%
B-2%
B+22%
O-3%
O+38%
ABO group: Group O Group A Group B Group AB

The eight blood types

A-
A negative
UK 8% · World 2%

Carries the A antigen but is Rh (D) negative.
A+
A positive
UK 30% · World 27%

A common type carrying the A antigen and Rh (D) positive.
AB-
AB negative
UK 1% · World 1%

The rarest of the eight main blood types.
AB+
AB positive
UK 2% · World 5%

The "universal recipient" — carries A, B and Rh antigens.
B-
B negative
UK 2% · World 2%

Carries the B antigen but is Rh (D) negative — one of the rarer types.
B+
B positive
UK 8% · World 22%

Carries the B antigen and Rh (D) positive.
O-
O negative
UK 13% · World 3%

The "universal donor" for red blood cells — no A, B or Rh antigens.
O+
O positive
UK 35% · World 38%

The most common blood type — no A or B antigens, but Rh (D) positive.
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