You can be one of eight different blood groups, namely O+, O-, B+, B-, A+, A-, AB+ or AB-. Your blood group is determined by the presence of small proteins on your red cells (called antigens):
- If you are Group A, you have A proteins on your red cells
- If you are Group B, you have B proteins on your red cells
- If you are Group AB, you have A and B proteins on your red cells
- If you are Group O, you have neither A nor B proteins on your red cells
The words ‘positive’ or ‘negative’ that follow your ABO blood group refer to the presence of a different protein on your red cell called RhD:
- You are ‘positive’ if you have RhD proteins on your red cells or ‘negative’ if you don’t.
Blood groups are important because patients must receive the correct type of blood according to their blood group. The tricky part is that there are antibodies in patients’ blood that can attack the A or B red cell proteins if someone is given blood that is not the correct group, which can be very dangerous.
It is not necessary for you to know your blood group, because in the event that you ever require a blood transfusion, we will check this ourselves and make sure you receive compatible blood.
Group O individuals are known as “universal donors” because their blood can be given to any patient, regardless of their blood group. The reason for this is that the Group O red cells don’t have A or B proteins on their surface, so blood group antibodies cannot harm them. Type O blood is very useful in emergency situations when there is not time to confirm the blood group of the patient before transfusion.
Group AB individuals, on the other hand, are known as “universal recipients”. This means that they can receive any type of blood because they lack the antibodies that can react with the A and B proteins on the red cells.