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Blood Group Basics


There are eight blood groups and they are classified using two systems.

  • ABO System
  • Rhesus system


ABO System

The first system is called the ABO System and it has four main groups:

  • O Group
  • A Group
  • B Group
  • AB Group


Rhesus System

The second system is called the Rhesus System and is classified as Rhesus Positive (+) and Rhesus Negative (-). The two systems combine to define the following of eight different blood groups of O-, O+, A-, A+, B-, B+, AB- and AB+.

Blood Group Compatibility

The table below demonstrates blood type compatibility. A person with AB+ blood type can receive blood from all of the major blood type groups. At the other extreme people with O- blood type can only receive blood from donors with the same blood type.

Blood GroupGives to these groupsReceives from these groups
O NegativeAllO- only
O Positive AB+, A+, B+, O+O- and O+
A Negative AB-, AB+, A+, A-O- and A-
A Positive AB+ and A+O-, O+, A-, A+
B Negative B-, B+, AB-, AB+O- and B-
B Positive B+ and AB+O-, O+, B-, B+
AB Negative AB- and AB+O-, A-, B-, AB-
AB Positive AB+ onlyAll


Irish Blood Group Type Frequency Distribution

Blood group O Positive is the most common group in Ireland while AB negative is the least common.

Blood GroupPercentage
O Positive47
A Positive26
B Positive9
O Negative8
A Negative5
B Negative2
AB Positive2
AB Negative1


Current Blood Supply

View the Current Blood Supply here.

National Blood Centre, James's Street, Dublin 8.       Tel: 00 353 1 4322800       Fax: 00 353 1 4322930