Blood Groups and Types

Human blood is grouped into 4 types: A, B, AB, and O. Each letter refers to a kind of antigen, on the surface of red blood cells. 

The Rh factor

Each blood type is also grouped by its Rhesus factor. Blood is either Rh positive (Rh+) or Rh negative (Rh-). About 87% of Americans have Rh+ blood. 

Rhesus refers to another type of antigen, or protein, on the surface of red blood cells. The name Rhesus comes from Rhesus monkeys, in which the protein was discovered.

Blood Transfusions 

Blood types become especially important when a blood transfusion is necessary. In a blood transfusion, a patient must receive a blood type that is well-matched with his or her own blood type—that is, the donated blood must be conventional by the patient's own blood. If the blood types are not compatible, red blood cells will clump together, making clots that can block blood vessel and cause death. 

Type O– blood is careful the worldwide donor because it can be donated to people of any blood type. Type AB+ blood is considered the worldwide recipient because people with this type can receive any blood type. 

Blood type	Percent of Americans with this type	Who can receive this type
O+	37%	O+, A+, B+, AB+
O-	6	All blood types
A+	34	A+, AB+
A-	6	A+, A–, AB+, AB–
B+	10	B+, AB+
B-	2	B+, B–, AB+, AB–
AB+	4	AB+
AB-	1	AB+, AB–

Did You Know?

•Certain blood types are more common in certain country. In China, over 99% of the population has Rh+ blood. 

•Different kinds of animals have different kinds of blood. Dogs have 4 blood types; cats have 11; cows have about 800. 

•Some people think blood type tells about character. Legend has it that Type A is calm and dependable; Type B is creative and excitable; Type AB is thoughtful and emotional; and Type O is a sure leader.

•In Japan, the idea of blood type as personality type is so popular that Japanese ask “What's your blood type?” about as often as Americans ask “What's your sign?”