Blood Group and It’s Compatibility

Although all blood is made of the same basic elements, not all blood is alike. In fact, there are four main blood groups, which are determined by the presence or absence of certain antigens – substances that can trigger an immune response if they are foreign to the body. Since some antigens can trigger a patient’s immune system to attack the transfused blood, safe blood transfusions depend on careful blood typing and cross-matching.

There are four main blood groups defined by the ABO system:
• blood group A – has A antigens on the red blood cells with anti-B antibodies in the plasma
• blood group B – has B antigens with anti-A antibodies in the plasma
• blood group O – has no antigens, but both anti-A and anti-B antibodies in the plasma
• blood group AB – has both A and B antigens, but no antibodies

*Blood group O is the most common blood group.

Source: Antranik


Red blood cells sometimes have another antigen, a protein known as the D antigen or Rhesus factor (Rh). If this is present, your blood group is Rh positive (Rh+). If it’s absent, your blood group is Rh negative (Rh-).

This means you can be one of eight blood groups:

  • A Rh positive (A+)
  • A Rh negative (A-)
  • B Rh positive (B+)
  • B Rh negative (B-)
  • O Rh positive (O+)
  • O Rh negative (O-)
  • AB Rh positive (AB+)
  • AB Rh negative (AB-)

Source: Sciencewithmyrt



There are very specific ways in which blood types must be matched for a safe transfusion.

Source: AmericanRedCross



  1. American Red Cross
  2. NHS Choices
  3. Antranik
  4. Science with Myrt
  5. The blood connection