How do I find out my blood type?
Give blood, if you can. It’s the usual free way in the UK. GPs don’t routinely test it. Home kits are quicker, but 1 in 6 home readings in one study didn’t match medical records.
On this page
How can I find out my blood type?
Give blood. NHS Blood and Transplant tests your first donation and tells you your type a few weeks later. It then shows in your online donor account and the NHS Give Blood app.
Asking your GP rarely works. The NHS says GPs do not routinely check blood groups. And you can’t usually find it in the NHS App.
| Way | What happens | Good to know |
|---|---|---|
| Give blood | Your first donation is tested. You get your type a few weeks later. | Free. First-timers must be 17 to 65 and weigh 50kg to 158kg. |
| What’s Your Blood Type event | You sign up as a donor, then have a free finger-prick test. It takes about 5 minutes. | Gives your likely type. It’s confirmed when you give blood. |
| Pregnancy | Every pregnant woman has a blood group test. | It’s offered at your first antenatal appointment, at 8 to 12 weeks. |
| Home kit | You prick your finger and read a card yourself. | Quick, but less reliable. |
Sources: NHS Blood and Transplant; NHSBT: who can give blood; NHS: blood groups; NHS: HDFN
You must also be generally fit and well. You’ll need to wait if you’re ill, pregnant, had a baby in the last 6 months or had a recent tattoo or piercing.
Not sure you can give? Call NHS Blood and Transplant on 0300 123 23 23 before you book.
How does a blood group test work?
Your red blood cells carry markers called antigens. Your plasma, the liquid part of blood, carries antibodies. The NHS says these decide your blood group.
How a lab finds your group
- 1
Take blood
A sample from a vein, or a few drops from a finger.
- 2
Add antibodies
Your red cells are mixed with anti-A, then anti-B.
- 3
Look for clumps
Clumps with anti-B but not anti-A mean group B.
- 4
No clumps
No reaction to anti-A or anti-B means group O.
Source: NHS: blood groups
Think of antigens as name badges on your cells. Antibodies are guards that attack certain badges your cells don’t carry.
That’s why getting blood from the wrong group can be life-threatening. Someone in group B has anti-A guards, so they attack group A cells.
| Group | Badges on red cells (antigens) | Guards in plasma (antibodies) |
|---|---|---|
| A | A | Anti-B |
| B | B | Anti-A |
| AB | A and B | None |
| O | None | Anti-A and anti-B |
Sources: NHS: blood groups; NHS Blood and Transplant
The plus or minus is a separate badge called RhD. Have it and you’re RhD positive. Lack it and you’re negative. That makes 8 blood groups in all.
When you get your result, write down the plus or minus too. A+ and A- are different blood types.
Are at home blood type tests accurate?
The card itself did well in one study. US researchers tested 200 hospital samples with a home card. It matched the hospital lab’s positive or negative result in 199 of them.
At home it did less well. In a US study, 288 people aged 14 to 50 did and read their own card. Where a medical record showed their type, their reading matched it 83.5% of the time.
Sources: Younes 2023; Dethier 2025
That’s the 1 in 6 from the top of this page. A clinician reading the same cards matched the record 92.3% of the time. Both studies checked only the positive or negative part.
Used a home kit? Treat the answer as your likely type until giving blood confirms it. For more on doing these tests well, see how to do a finger-prick test and how accurate finger-prick tests are.
What are the most common blood types in the UK?
O positive. The NHS says almost half the UK, around 48%, is group O. About 85% of people are RhD positive.
| Blood type | Share of UK donors |
|---|---|
| O positive | 36% |
| A positive | 28% |
| O negative | 14% |
| A negative | 8% |
| B positive | 8% |
| B negative | 3% |
| AB positive | 2% |
| AB negative | 1% |
These are donors, not everyone, and they’re rounded. O negative is called the universal type. NHS Blood and Transplant says it’s safe for everyone to receive O negative red cells. The NHS says that’s true in most cases.
The NHS says O negative is often used in emergencies when a patient’s type isn’t known yet. If you find you’re O negative, that’s one more reason to keep giving.
Why does my blood type matter?
It comes up in two main places: getting blood and having a baby. Before a transfusion, the hospital tests your blood against donor cells anyway. So knowing your type won’t replace that check.
In pregnancy, the minus matters. If you’re RhD negative and your baby is positive, you may make antibodies that break down your baby’s red blood cells. That’s called haemolytic disease of the fetus and newborn (HDFN).
So if you’re negative, the NHS tests your baby’s type from a sample of your blood. If the baby is positive, you’ll be offered an anti-D injection to stop those antibodies forming.
Your blood type checklist
- Check you can give blood: first-timers must be 17 to 65 and weigh 50kg to 158kg.
- Book on the NHS Blood and Transplant website or call 0300 123 23 23.
- Can’t give blood yet? Look for a What’s Your Blood Type event near you.
- Used a home kit? Treat the answer as your likely type until giving blood confirms it.
- Write your type down with the plus or minus. A+ and A- are different blood types.
- Pregnant and RhD negative? Ask your midwife about the anti-D injection.
Sources: NHS Blood and Transplant; NHSBT: who can give blood; NHS: HDFN
Curious what else the NHS won’t test on request? See blood tests the NHS won’t do.
When to speak to a GP
Your blood type isn’t a health problem, so there’s nothing to treat. Speak to a GP or midwife if:
- You’re pregnant and haven’t had your first antenatal appointment. The blood test is offered at 8 to 12 weeks.
- You’re pregnant and RhD negative, and want to know if you need the anti-D injection.
- You’ve been told you have antibodies from a past transfusion or pregnancy, and you’re pregnant again.
- A home kit says you’re negative and you’re pregnant. Tell your midwife rather than relying on the card.
Contact your doctor, midwife or health visitor urgently if you’ve been told your baby may have HDFN and they show signs of jaundice or anaemia.
Jaundice signs are yellow skin or whites of the eyes, dark yellow pee or pale poo. On brown or black skin, yellowing is easier to see on the palms or soles.
Anaemia signs are pale skin and breathing faster than usual. On brown or black skin, paleness is easier to see on the nails or inside the eyelids. With either, your baby may be sleepy and not feeding as well as usual.
Want to read the rest of your NHS results? See NHS App blood test results.