Blood Groups

ABO & Rh Blood Group Systems Explained

5 min readREDDAR Radar Room

Understanding blood groups is essential not just for medical professionals but for every potential donor and recipient. The ABO and Rh systems are the most clinically significant.

The ABO System

The ABO blood group system classifies blood into four types based on the presence or absence of antigens on red blood cells: A, B, AB, and O.

  • Type A: Has A antigens, anti-B antibodies
  • Type B: Has B antigens, anti-A antibodies
  • Type AB: Has both antigens, no antibodies (universal recipient)
  • Type O: No antigens, both anti-A and anti-B antibodies (universal donor)

The Rh System

The Rh factor refers to the presence (+) or absence (–) of the RhD antigen. A person is either Rh-positive or Rh-negative. This matters enormously during pregnancy and transfusions.

Why O Negative is the Universal Donor

O negative blood can be given to anyone regardless of their blood type. This makes it invaluable in emergencies when there's no time to determine the patient's blood type. O negative donors are always in critical demand.

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