Quick answer
B positive (B+) means red blood cells carry the B antigen and the RhD antigen. B+ red cells can generally be given to B+ and AB+ recipients, and B+ people can generally receive red cells from B+, B−, O+, and O− donors.
What B+ means
The B indicates the B antigen is present on red cells, with anti-A antibodies typically in plasma. The plus sign indicates the RhD antigen is present.
Because B+ people carry anti-A antibodies, they should not receive red cells with the A antigen (types A and AB).
B positive is less common than O and A types in many populations but is still widely represented among donors.
| Property | Value |
|---|---|
| ABO group | B |
| Rh (D) status | Positive (RhD antigen present) |
| Red cell antigens | B, RhD |
| Plasma antibodies (typical) | anti-A |
Compatibility summary
General red cell and plasma compatibility for B+ 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 | B+, AB+ | O−, O+, B−, B+ |
| Plasma (ABO only) | B, O | B, AB |
See the full compatibility chart for all eight types.
Inheritance context
Type B can result from BB or BO genotypes. The B allele is dominant over O.
Two type B parents can have type B or type O children under the standard model. A type B and a type A parent can have children of any ABO type.
Rh-positive status can be DD or Dd, so a B+ person may or may not carry a d allele.
Work through specific parent combinations with the baby blood type calculator, or find which parent types could produce a B+ 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.