Quick answer
A positive (A+) means red blood cells carry the A antigen and the RhD antigen. A+ red cells can generally be given to A+ and AB+ recipients, and A+ people can generally receive red cells from A+, A−, O+, and O− donors.
What A+ means
The letter A indicates that red cells display the A antigen on their surface and that the plasma typically contains anti-B antibodies. The plus sign indicates the RhD antigen is present.
Because A+ people have anti-B antibodies, they should not receive red cells carrying the B antigen (types B and AB). Because they are Rh-positive, they can receive either Rh-positive or Rh-negative red cells.
A positive is one of the more common blood types in many populations, which generally makes compatible red cells easier to source for A+ recipients.
| Property | Value |
|---|---|
| ABO group | A |
| Rh (D) status | Positive (RhD antigen present) |
| Red cell antigens | A, RhD |
| Plasma antibodies (typical) | anti-B |
Compatibility summary
General red cell and plasma compatibility for A+ 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 | A+, AB+ | O−, O+, A−, A+ |
| Plasma (ABO only) | A, O | A, AB |
See the full compatibility chart for all eight types.
Inheritance context
A person with type A blood may have inherited two A alleles (AA) or one A allele and one O allele (AO). The A allele is dominant over O, so both genotypes appear as type A.
Rh-positive status can come from two D alleles (DD) or one D and one d (Dd). Two Rh-positive parents can therefore still have an Rh-negative child if both carry a d allele.
Two type A parents can have type A or type O children under the standard model, but not type B or AB.
Work through specific parent combinations with the baby blood type calculator, or find which parent types could produce a A+ 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.