What Does O Positive Blood Type Mean?
Having O positive (O+) blood type means you have red blood cells that lack both A and B antigens on their surface (making you blood group O in the ABO system) and possess the RhD antigen (making you Rh positive). 1
ABO Blood Group Component
Your red blood cells do not express A or B antigens, which defines you as blood group O. 1 This is the most common blood type in many populations and occurs when you inherit O alleles that do not encode functional glycosyltransferases needed to create A or B antigens. 2
- As a recipient: You can only receive O positive or O negative blood, since you naturally have antibodies against both A and B antigens in your plasma. 1
- As a donor: Your blood can be given to patients with A+, B+, AB+, or O+ blood types, making you a relatively universal donor for Rh positive recipients. 1
Rh (RhD) Component
The "positive" designation means your red blood cells express the RhD antigen. 1 Approximately 85% of people are Rh positive. 1
- Clinical significance for women: If you are a woman of childbearing potential with O positive blood, you do not require RhD negative blood in emergency situations, unlike RhD negative women who need RhD negative blood to prevent alloimmunization and potential hemolytic disease of the newborn in future pregnancies. 1
- Emergency transfusion: In life-threatening hemorrhage when your blood type is unknown, you would ideally receive O RhD negative blood, but O RhD positive blood is acceptable for males and postmenopausal females. 1
Clinical Implications
For routine transfusions: Pre-transfusion testing determines your ABO and RhD status to detect any red cell antibodies and confirm compatibility with donor units, a process that typically takes approximately 45 minutes. 1
In emergency situations: Group-specific blood (O positive in your case) can be rapidly issued within 10-20 minutes of the laboratory receiving a properly labeled sample, which is safer than using universal donor O negative blood when time permits identification. 1
Disease associations: Population studies have identified that O blood group is associated with slightly decreased risks for certain conditions, including kidney stones and SARS-CoV-2 infection, compared to other blood groups. 3, 4