Blood group compatibility.
Pick your group below and see, in plain words, who you can give blood to and who can save you. The full donor-to-patient table is further down.
Pick your blood group
If you are O-, you can give to
O- · O+ · B- · B+ · A- · A+ · AB- · AB+
8 of 8 groups can safely receive your red cells.
If you need blood, O- can receive from
O-
1 of 8 groups can save you.
You are the universal red cell donor. Any patient in Nigeria can take your blood, which is why hospitals call O− first in an emergency — and why O− runs out fastest.
Full compatibility chart
Rows are the patient receiving blood. Columns are the donor. A filled cell means that transfusion is safe for red cells. O− can give to everyone; AB+ can receive from everyone.
| Patient \ Donor | O- | O+ | B- | B+ | A- | A+ | AB- | AB+ |
|---|---|---|---|---|---|---|---|---|
| O- | ✓ | – | – | – | – | – | – | – |
| O+ | ✓ | ✓ | – | – | – | – | – | – |
| B- | ✓ | – | ✓ | – | – | – | – | – |
| B+ | ✓ | ✓ | ✓ | ✓ | – | – | – | – |
| A- | ✓ | – | – | – | ✓ | – | – | – |
| A+ | ✓ | ✓ | – | – | ✓ | ✓ | – | – |
| AB- | ✓ | – | ✓ | – | ✓ | – | ✓ | – |
| AB+ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
Blood group and genotype are not the same test
In Nigeria the two are usually checked together, so people often mix them up. They answer different questions.
Blood group
A, B, AB or O, plus positive or negative. It describes the markers on your red cells and it decides whose blood can safely be transfused into you. This is the test that matters for donating and receiving blood.
Genotype
AA, AS, SS and other combinations. It describes the haemoglobin genes you inherited and it is what sickle cell screening looks at. It is a separate result from your blood group — an O+ person can have any genotype.
Questions about what a genotype result means for you or your family belong with a doctor, not a web page. Background reading: WHO on blood transfusion safety.
Common questions
- How many blood groups are there?
- Eight in everyday use. Four ABO groups — A, B, AB and O — each in a positive or a negative version. That is where A+, A−, B+, B−, AB+, AB−, O+ and O− come from.
- What do the plus and minus mean?
- They stand for the Rhesus (Rh) factor. Positive means your red cells carry the RhD protein; negative means they do not. A negative patient must not be given positive blood, which is why negative groups are always in shorter supply.
- Which blood group is the universal donor?
- O negative. O− red cells carry none of the A, B or RhD markers, so any patient can receive them. That makes O− the group hospitals reach for before a patient's own group is confirmed.
- Which blood group is the universal recipient?
- AB positive. An AB+ patient can safely receive red cells from all eight groups.
- Why does O negative matter most in an emergency?
- When a patient is bleeding out, there is no time to type and cross-match. O− can be given straight away to anyone, so it is the group emergency rooms burn through and the hardest one to replace.
Now put your group to work
Spark Blood matches patients in Nigerian hospitals with nearby donors of the right group, in minutes rather than hours.