Quick answer
O positive (O+) means red blood cells carry neither the A nor B antigen but do carry the RhD antigen. O+ red cells can generally be given to O+, A+, B+, and AB+ recipients, and O+ people can generally receive red cells only from O+ and O− donors.
What O+ means
O indicates no A or B antigens on red cells. Plasma from type O people typically contains both anti-A and anti-B antibodies, which is why O recipients can only receive type O red cells.
The plus sign indicates the RhD antigen is present, so O+ recipients can receive either Rh-positive or Rh-negative red cells.
O positive is the most common blood type in many populations and is heavily relied on by blood services for Rh-positive recipients.
| Property | Value |
|---|---|
| ABO group | O |
| Rh (D) status | Positive (RhD antigen present) |
| Red cell antigens | RhD |
| Plasma antibodies (typical) | anti-A, anti-B |
Compatibility summary
General red cell and plasma compatibility for O+ under the simplified ABO/Rh model. Real transfusions also depend on antibody screening and crossmatching.
| Product | Can give to | Can receive from |
|---|---|---|
| Red blood cells | O+, A+, B+, AB+ | O−, O+ |
| Plasma (ABO only) | O | A, B, AB, O |
See the full compatibility chart for all eight types.
Inheritance context
Type O has only the OO genotype under the standard model. Each parent must have contributed an O allele, so parents may be type A (AO), B (BO), or O (OO), but not AB.
Rh-positive status can be DD or Dd.
Two type O parents are expected to have only type O children under the standard model.
Work through specific parent combinations with the baby blood type calculator, or find which parent types could produce a O+ child with the parent calculator.
Limitations
- Blood type can only be confirmed by laboratory testing. Family history, calculators, and self-report are not substitutes.
- Compatibility rules on this page are general educational summaries. Real transfusion decisions also depend on antibody screening, crossmatching, product type, and clinical judgment.
- Rare variants such as the Bombay phenotype, cis-AB, and weak or partial D expression can produce results that differ from the simplified ABO/Rh model.