Blood test
Blood Group and Crossmatch
This test identifies your blood group and checks compatibility so that blood can be given safely if you need a transfusion.
Quick answer
Blood Group and Crossmatch: what it is and what the results mean
Blood grouping determines your ABO group and Rhesus (Rh) type and screens for antibodies. A crossmatch then tests your blood against donor blood to confirm it is compatible before a transfusion.
- Why it is done: It is done before surgery or procedures where a transfusion may be needed, in pregnancy, and whenever someone may require donor blood, to make sure any blood given is a safe match.
- Understanding results: The result gives your ABO and Rh type (for example O positive) and whether any antibodies are present.
What it is
Blood grouping determines your ABO group and Rhesus (Rh) type and screens for antibodies. A crossmatch then tests your blood against donor blood to confirm it is compatible before a transfusion.
Why it is done
It is done before surgery or procedures where a transfusion may be needed, in pregnancy, and whenever someone may require donor blood, to make sure any blood given is a safe match.
What to expect
It is an ordinary blood test from a vein in the arm. A “group and save” records your blood group and antibody screen; a full crossmatch is done when a transfusion is likely.
Understanding the results
The result gives your ABO and Rh type (for example O positive) and whether any antibodies are present. Compatible donor blood is then selected. In pregnancy, Rh status guides whether anti-D treatment is needed.
Good to know
Risks and limitations
It is a very safe blood test. Samples must be labelled with great care because errors could lead to an incompatible transfusion, so identity checks are strict.
Education and reference only. This explains the test in general terms and is not medical advice. Always follow the specific instructions from the team arranging your test, and discuss your results with your clinician.
Answers
Blood Group and Crossmatch: frequently asked questions
What is the difference between “group and save” and a crossmatch?
A group and save records your blood type and screens for antibodies but does not reserve blood, while a crossmatch specifically matches and prepares donor units for you when a transfusion is likely.
Why is blood group important in pregnancy?
Your Rhesus (Rh) status matters because an Rh-negative mother carrying an Rh-positive baby may need anti-D injections to prevent antibodies that could affect this or future pregnancies.
Related tests
Other blood test investigations
Sources
Where this is drawn from
- NHS — Tests and treatments
- NICE — diagnostic guidance
- British Society for Haematology / relevant professional body
Building patient-education content for tests or procedures?
We create clear, accurate, referenced medical explainers and decision aids for teams.