What it measures
- ABO blood group
- Rhesus (RhD) factor
Why know your blood group?
Your blood group never changes, so it’s useful to know for your medical records, travel and blood donation. It matters most in pregnancy.
Blood groups and pregnancy
If you’re RhD negative and your baby is RhD positive, your body can make antibodies against your baby’s blood cells. This rarely affects a first pregnancy but can affect later ones. It’s prevented with anti-D injections, which your NHS maternity team will arrange if you need them. Knowing your blood group early helps you understand your care plan.
You’ll receive a clear report showing your ABO group and RhD status.
Who it’s for
- Pregnancy or planning a pregnancy
- Curiosity, travel or personal medical records
- Before donating blood
How to prepare
- Drink plenty of water beforehand; it makes the sample quicker and easier to take.
- You don’t need to fast.
Blood Group Test: your questions
What is the most common blood group in the UK?
O positive is the most common blood group in the UK, followed by A positive.
Can my blood group change?
No. Your blood group is inherited and stays the same throughout your life, except in very rare cases such as after a bone marrow transplant.
Information on this page is general and doesn’t replace advice from your GP, midwife or consultant. If you feel unwell or are worried about symptoms, contact your GP, call NHS 111 or, in an emergency, 999.