Free blood compatibility checker: see who you can donate to and receive from by ABO and Rh type, with universal donor status.
Blood transfusion compatibility depends on a simple but critical principle: donated blood must not carry antigens that the recipient's immune system will attack. The ABO system (types A, B, AB, O) and the Rh factor (positive or negative) together determine who can safely give blood to whom.
This checker shows you exactly which blood types are safe donors and recipients for any given blood type. If you know your Rh factor, enter it for precise results including Rh compatibility. If you don't know your Rh factor, select 'Unknown' to see ABO-level compatibility.
The compatibility matrix visualizes all 8×8 donor-recipient pairs — green cells show compatible combinations, and your selected type is highlighted. Use it to understand why O-negative is the universal donor and AB-positive is the universal recipient.
This tool follows standard ABO/Rh transfusion protocols used worldwide. It provides educational information — always consult medical professionals for actual transfusion decisions.
Transfusion compatibility depends on antigen-antibody reactions. If donated blood has antigens that the recipient's immune system recognizes as foreign, antibodies will attack the donor cells. Type O blood has no A or B antigens, making it safe for anyone in ABO terms. Rh- donors can give to both Rh+ and Rh- recipients, but Rh- recipients should only receive Rh- blood to avoid developing anti-Rh antibodies.
O-negative (O-) is the universal donor because red blood cells completely lack A, B, and Rh antigens — meaning no recipient will have an immune reaction against them. AB-positive (AB+) is the universal recipient because their plasma has no anti-A or anti-B antibodies and can accept both Rh+ and Rh- blood. In emergencies when the patient's blood type is unknown, O- blood is used first.
No. Rh-negative patients should only receive Rh-negative blood to avoid Rh sensitization — a condition where the immune system produces antibodies against the Rh antigen, which can cause dangerous reactions in future transfusions or pregnancies. Rh-positive patients can safely receive both Rh+ and Rh- blood. If you don't know your Rh status, use the 'Unknown' option to see ABO-level compatibility.
AB plasma contains no anti-A or anti-B antibodies, and Rh+ recipients can accept both Rh+ and Rh- red cells. So AB+ can receive red blood cells from any ABO/Rh type in an emergency.
Yes, but eligibility rules are about the donor's health, not just type. Some countries ask donors to avoid recent tattoos, travel, or illnesses; type O- donors are especially valuable because their blood can be used for anyone.
It can be compatible, but family donation still requires the same cross-matching. Some hospitals discourage directed donation from partners because of transfusion-related reactions in pregnant women — always follow your blood bank's guidance.