Select an ABO blood group and Rh factor to see which blood types can donate to it and which blood types it can donate to, based on standard transfusion compatibility rules.
Important: This tool is for general information and education only. It is never a basis for an actual transfusion decision. Real transfusions always require laboratory cross-matching and confirmation by a qualified health professional.
Compatibility for this blood type
This blood type can donate red cells to:
This blood type can receive red cells from:
These are general ABO and Rh transfusion rules for red blood cells. A real transfusion always requires laboratory cross-matching and testing by a qualified professional, since other blood factors can also affect compatibility.
| Blood type | Can donate to | Can receive from |
|---|
How ABO and Rh compatibility works
Red blood cells carry A and B antigens on their surface, and the plasma carries antibodies against whichever antigens are absent. A group A person has anti-B antibodies, a group B person has anti-A antibodies, group O has both, and group AB has neither. A transfusion is only safe when the donated red cells do not carry an antigen the recipient has antibodies against. The Rh factor adds a simple rule on top of this: an Rh-negative person should only receive Rh-negative blood, while an Rh-positive person can receive either Rh-positive or Rh-negative blood.
Blood donation in the UK
NHS Blood and Transplant runs blood donation across England, with equivalent services in Scotland, Wales and Northern Ireland. The NHS regularly appeals for more O negative and B negative donors, since O negative is needed for emergencies and both groups are in shorter supply relative to demand than A and O positive. Donors can give whole blood roughly every 12 weeks, and NHS Blood and Transplant also collects plasma and platelets separately at dedicated donor centres, which follows a different eligibility and frequency schedule from whole blood donation.
Why O negative and AB positive matter
O negative red cells carry neither A nor B antigens and no Rh factor, so they do not trigger an immune reaction in any recipient, which is why O negative is called the universal donor and is kept in reserve for emergencies. AB positive works the opposite way: since an AB positive person already carries both A and B antigens and the Rh factor, their plasma has no antibodies left to react against, so they can receive red cells from any group, making AB positive the universal recipient.
What this tool cannot tell you
This tool only covers the standard ABO and Rh red cell rules. It does not account for rarer blood group systems, plasma or platelet compatibility (which follow different rules from red cells), or the antibody screening and cross-matching a laboratory performs before any real transfusion.
This tool is for general information only and is not a medical device. A real transfusion always requires laboratory testing and the decision of a qualified health professional. All calculations happen in your browser; nothing you enter is saved or sent anywhere.