Question 1

What determines blood type?

Accepted Answer

Blood type is determined by the presence or absence of antigens (A and B) on red blood cells and the Rh factor (positive or negative). This gives the 8 main blood types: A+, A-, B+, B-, AB+, AB-, O+, O-. Blood type is genetically inherited from your parents and remains constant throughout your life.

Question 2

What is the universal donor and universal recipient?

Accepted Answer

O- (O negative) is the universal red blood cell donor — it can be given to any blood type because it lacks A, B, and Rh antigens that could cause immune reactions. AB+ (AB positive) is the universal red blood cell recipient — it can receive from any type. Note these rules differ for plasma and platelets: AB is the universal plasma donor, and O is the universal plasma recipient.

Question 3

What happens if you receive incompatible blood?

Accepted Answer

A transfusion with incompatible blood can cause a hemolytic transfusion reaction, where the immune system attacks the donor blood cells. This causes symptoms ranging from mild (fever, chills) to severe (kidney failure, shock, death in serious cases). This is why blood type testing before transfusion is critical in medical settings.

Question 4

What blood type is most common?

Accepted Answer

Blood type frequency varies by population. Globally, O+ is the most common (about 38%), followed by A+ (27%), B+ (22%), AB+ (6%), O- (7%), A- (6%), B- (2%), and AB- (1%). East Asian populations have higher B frequency, while Native American populations are predominantly O.

Question 5

What is Rh incompatibility in pregnancy?

Accepted Answer

Rh incompatibility occurs when an Rh-negative mother carries an Rh-positive baby. During delivery, fetal blood can enter the mother's circulation, causing her to develop Rh antibodies. In subsequent pregnancies, these antibodies can cross the placenta and damage the Rh-positive fetus's red blood cells (hemolytic disease of the newborn). This is prevented with Rh immunoglobulin (RhIg) shots during pregnancy.

Donor ↓ / Recipient →	A+	A-	B+	B-	AB+	AB-	O+	O-
A+	✓	–	–	–	✓	–	–	–
A-	✓	✓	–	–	✓	✓	–	–
B+	–	–	✓	–	✓	–	–	–
B-	–	–	✓	✓	✓	✓	–	–
AB+	–	–	–	–	✓	–	–	–
AB-	–	–	–	–	✓	✓	–	–
O+	✓	–	✓	–	✓	–	✓	–
O-	✓	✓	✓	✓	✓	✓	✓	✓

Blood Type Compatibility

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Comments & Feedback

Donor ↓ / Recipient →	A+	A-	B+	B-	AB+	AB-	O+	O-
A+	✓	–	–	–	✓	–	–	–
A-	✓	✓	–	–	✓	✓	–	–
B+	–	–	✓	–	✓	–	–	–
B-	–	–	✓	✓	✓	✓	–	–
AB+	–	–	–	–	✓	–	–	–
AB-	–	–	–	–	✓	✓	–	–
O+	✓	–	✓	–	✓	–	✓	–
O-	✓	✓	✓	✓	✓	✓	✓	✓

Donor ↓ / Recipient →	A+	A-	B+	B-	AB+	AB-	O+	O-
A+	✓	–	–	–	✓	–	–	–
A-	✓	✓	–	–	✓	✓	–	–
B+	–	–	✓	–	✓	–	–	–
B-	–	–	✓	✓	✓	✓	–	–
AB+	–	–	–	–	✓	–	–	–
AB-	–	–	–	–	✓	✓	–	–
O+	✓	–	✓	–	✓	–	✓	–
O-	✓	✓	✓	✓	✓	✓	✓	✓

Donor ↓ / Recipient →	A+	A-	B+	B-	AB+	AB-	O+	O-
A+	✓	–	–	–	✓	–	–	–
A-	✓	✓	–	–	✓	✓	–	–
B+	–	–	✓	–	✓	–	–	–
B-	–	–	✓	✓	✓	✓	–	–
AB+	–	–	–	–	✓	–	–	–
AB-	–	–	–	–	✓	✓	–	–
O+	✓	–	✓	–	✓	–	✓	–
O-	✓	✓	✓	✓	✓	✓	✓	✓