Quick answer
A negative (A−) means red blood cells carry the A antigen but not the RhD antigen. A− red cells can generally be given to A−, A+, AB−, and AB+ recipients, and A− people can generally receive red cells only from A− and O− donors.
What A− means
The A indicates the A antigen is present on red cells, with anti-B antibodies typically in plasma. The minus sign indicates the RhD antigen is absent.
Rh-negative recipients are generally given Rh-negative red cells to avoid forming anti-D antibodies. This narrows the compatible donor list for A− people to A− and O−.
A− red cells are useful to blood services because they can be given to both Rh-negative and Rh-positive recipients of type A and AB.
| Property | Value |
|---|---|
| ABO group | A |
| Rh (D) status | Negative (RhD antigen absent) |
| Red cell antigens | A |
| 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−, A+, AB−, AB+ | O−, A− |
| Plasma (ABO only) | A, O | A, AB |
See the full compatibility chart for all eight types.
Inheritance context
Type A can result from AA or AO genotypes. Rh-negative status requires two d alleles (dd), meaning each parent contributed a d allele.
An A− person's parents could each be Rh-positive (if both are Dd) or Rh-negative. The ABO side could come from A, B, AB, or O parents depending on their genotypes.
Rh-negative status is relevant during pregnancy; see the Rh factor and pregnancy page for how clinicians screen and manage it.
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.