Antibodies in the recipient’s plasma attack red cells with antigens they lack, so red cell compatibility follows the recipient’s antibodies. For plasma it is the reverse. Rh-negative people should receive Rh-negative red cells, especially girls and women who may become pregnant.
How to use the Blood Donor Compatibility Calculator
- ABO group
- Rh type
Results update as you type, and every field accepts the units shown in its menu.
How it works
Choose your ABO group and Rh type.
Inputs explained
| Field | What to enter |
|---|---|
| ABO group | Choose one: A, B, AB, O |
| Rh type | Choose one: Rh positive, Rh negative |
What each result means
- You can give red cells to = ([ABO group] – 1)×2 + [Rh type] – 1
- You can receive red cells from = ([ABO group] – 1)×2 + [Rh type] – 1
- You can give plasma to = [ABO group] – 1
- You can receive plasma from = [ABO group] – 1
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
Red cells: O− is the universal donor, AB+ the universal recipient
Plasma: AB is the universal plasma donor, O the universal plasma recipient
Worked example
Inputs — ABO group: O; Rh type: Rh positive.
Results — You can give red cells to = All Rh-positive types; You can receive red cells from = O+, O−; You can give plasma to = O only; You can receive plasma from = Everyone.
Key terms
- ABO
- Blood group system with A, B, AB and O types.
- Rh
- Rhesus D antigen (positive or negative).
Frequently asked questions
What is the universal donor?
O negative for red cells; AB for plasma.
What is the rarest blood type?
AB negative in most populations.
Why is O negative in such demand?
It can be given in emergencies before a patient's group is known.