A form asks for your blood group. Maybe it is a midwife, a travel plan or the donor centre. You half remember "A something", and you cannot say whether it was positive or negative.
The quickest way to know for certain is a blood group test at Blood London: one blood sample at 117a Harley Street, which reports your ABO group and your RhD status. The test is £83.75 plus the £50 blood draw, £133.75 in total, with your result in 2 days, and you can walk in any day. Book the Blood Group (ABO) test.
"Most people only want their blood group because something's come up: a trip, a pregnancy, giving blood. It's one small sample, and once you know it, you know it for life."
Dr Mohammad Bakhtiar, Clinical Lead, GMC 4694470
One result, read from left to right
Take a result that reads A positive. It has two parts, and each answers a different question.
The letter is your ABO group. Red blood cells can carry an A marker, a B marker, both or neither, and the test shows which you have: A, B, both (group AB) or neither (group O).
The word after it is your RhD status. Your cells either carry the RhD marker (positive) or lack it (negative). Four groups and two RhD results give eight possible answers:
| ABO group | If RhD present | If RhD absent |
|---|---|---|
| A | A positive | A negative |
| B | B positive | B negative |
| AB | AB positive | AB negative |
| O | O positive | O negative |
So A positive means you carry the A marker and the RhD marker.
Who can give blood to whom
The same two parts decide which donations suit which patients, which is why services ask for your group at all. A positive blood can go to A positive and AB positive patients, and an A positive patient can receive from A and O donors of either RhD type. Group O negative has no A, B or RhD markers, so it is the group hospitals reach for in an emergency, and AB positive patients can receive from every group.
Free ways to find out, and when a private test makes sense
You can find out your group without paying. Blood donation services tell their donors, and your maternity team checks it at your booking appointment if you are pregnant. Both depend on timing: a donor session may be weeks away, and the pregnancy check comes at a set point.
A private test suits the person who needs the answer now, for a form, a trip, a sports or work requirement, or simply to put the result in their own records. It is one sample, with the result in 2 days.
Hospitals test your blood themselves before any transfusion, so a private result is for planning and for your records, not a substitute for their checks.
What the visit involves
You come to 117a Harley Street, have one blood sample taken, and leave. We are open Monday to Friday 09:00 to 18:00 and Saturday and Sunday 10:00 to 14:00, and you can walk in without an appointment, as our guide to walk-in blood tests in London explains.
The 2 days run from when the sample reaches the lab, which happens the same day it is taken. Our guide to how long blood test results take shows how that clock works for other tests.
If you are having blood taken anyway, other tests can join the same visit, and the £50 draw is charged once. A full blood count gives a wider picture of your blood cells, and the Gold blood profile covers more markers in one go. You can browse the popular blood tests or see all our private blood tests in London.
Questions people ask
Does my blood group ever change?
It stays the same through your life, which is why one test is enough. A stem cell or bone marrow transplant is the main exception, because the donor's cells replace your own.
Might my blood group already be on record?
Possibly. If you have given blood, been pregnant or had surgery, a result may already exist. A donor card or your maternity notes would show it. If you cannot find one, the test above gives you a fresh result in 2 days.
Does the test tell me anything else about my health?
It reports your ABO group and your RhD status, nothing more. For a view of your blood cells, add the full blood count at the same visit.
Know your group in 2 days
One sample, one visit, and a result you keep for life. Walk in to 117a Harley Street any day, or book the Blood Group (ABO) test online for £83.75 plus the £50 draw.