You can find out your blood group by giving blood.
To find out someone’s blood group, a sample of their blood has to be taken and tested. However, GPs do not routinely check people’s blood groups.
When is someone’s blood group checked?
Healthcare professionals sometimes need to know a person’s blood group for medical reasons.
If you need a blood transfusion, the blood group you receive must be compatible with your own blood group. Your blood type will therefore be tested before you receive a blood transfusion, to make sure the two are compatible. Giving someone blood from the wrong group can be potentially life-threatening.
If you’re pregnant, your blood will be tested to see if it’s rhesus negative or positive. You can find information about rhesus disease in the Health A-Z. Some women are rhesus negative. This isn't usually a concern for a first pregnancy, but it may affect the next baby if you get pregnant again.
Healthcare professionals will also check a person’s blood group before they:
- give blood
- have an operation (surgery)
- donate an organ for transplant
Give blood and find out your blood group
Your blood group will be checked if you give blood through the National Blood Service, so it can be matched to someone with the same blood group or one that is compatible.
Some blood groups cannot be mixed with each other because chemicals in the blood (antigens) can attack one another, causing the blood to clot.
Your blood will be tested before you give blood, and your blood group will be recorded on your donor card.
Last Updated: 18 November 2011