Blood Type Compatibility Tool
Select donor and recipient blood types to check transfusion compatibility, see antigens and antibodies visualized on red blood cells, and explore blood type inheritance with an interactive Punnett square.
Select Blood Types
Donor
transfuse
Recipient
O- (universal donor) is biologically compatible with AB+, but in practice this type is reserved for emergencies when a matching type is unavailable. The recipient can receive a closer match from another blood type.
Donor antigens
None
Recipient antibodies
None
Red Blood Cell Antigen View
Compatible donors for AB+
Can donate O- to
Full Compatibility Matrix
Click any cell to select that donor/recipient pair.
| Donor ↓Recipient → | A+ | A- | B+ | B- | AB+ | AB- | O+ | O- |
|---|---|---|---|---|---|---|---|---|
| A+ | ||||||||
| A- | ||||||||
| B+ | ||||||||
| B- | ||||||||
| AB+ | ||||||||
| AB- | ||||||||
| O+ | ||||||||
| O- |
Reference Guide
ABO Blood Types
The ABO system classifies blood based on which antigens appear on the surface of red blood cells. A person inherits one allele from each parent.
| Type | Antigens | Antibodies |
|---|---|---|
| A | A antigen | Anti-B |
| B | B antigen | Anti-A |
| AB | A and B antigens | None |
| O | None | Anti-A and Anti-B |
AB+ individuals can receive any blood type (universal recipient) because they produce no ABO or Rh antibodies. O- individuals can donate to anyone (universal donor) because their red blood cells carry no antigens to trigger an immune response.
Rh Factor
The Rh factor (also called the D antigen) is a protein that may or may not appear on the surface of red blood cells. People who have it are Rh-positive; those who lack it are Rh-negative.
- Rh+ donor to Rh- recipient - Incompatible. The Rh- recipient will produce Anti-Rh antibodies. A second transfusion can trigger a severe reaction.
- Rh- donor to Rh+ recipient - Compatible. No Rh antigens are introduced, so no immune response occurs.
- Rh incompatibility in pregnancy - If an Rh- mother carries an Rh+ fetus, she may develop Anti-Rh antibodies that cross the placenta in subsequent pregnancies. RhoGAM injections prevent this sensitization.
About 85% of people are Rh-positive. The Rh system is the second most important blood group system after ABO.
Blood Type Inheritance
Blood type is controlled by the ABO gene with three alleles: IA (codes for A antigen), IB (codes for B antigen), and i (recessive, produces no antigen). Each parent passes one allele to each child.
| Genotype | Blood Type |
|---|---|
| IAIA or IAi | A |
| IBIB or IBi | B |
| IAIB | AB (codominant) |
| ii | O |
IA and IB show codominance: if a person inherits both, they express both antigens (AB type). The i allele is recessive; type O only appears when both alleles are i.
Clinical Context
Before any blood transfusion, hospitals perform a type and screen to identify the patient's ABO and Rh groups, then check for unexpected antibodies. A crossmatch test mixes donor blood with recipient serum to confirm compatibility directly.
- O- blood is used in emergencies when there is no time to determine a patient's blood type. Because supplies are limited, it is reserved for trauma and neonatal cases.
- Plasma transfusions follow the reverse rule: AB plasma (no antibodies) can be given to any recipient.
- Platelets are generally type-independent but ABO-matched platelets last longer in the recipient.
- Population frequency - O+ is the most common type worldwide (about 38% in the US). AB- is the rarest (about 1%).