Blood type is determined by the presence or absence of certain antigens on the surface of red blood cells. Antigens are substances that can trigger an immune response if they are foreign to the body. There are four major blood groups determined by the presence or absence of two antigens, A and B, on the surface of red blood cells. These groups are A, B, AB, and O. In addition to the A and B antigens, there is a protein called the Rh factor, which can be either present (+) or absent (-), creating the 8 most common blood types (A+, A-, B+, B-, O+, O-, AB+, AB-) . Blood type is inherited from your parents, like eye color.

Here is a summary of the blood types and their antigens:

• Type A: has A antigens on the surface of red blood cells
• Type B: has B antigens on the surface of red blood cells
• Type AB: has both A and B antigens on the surface of red blood cells
• Type O: has neither A nor B antigens on the surface of red blood cells

Each of these types is then further classified based on the presence or absence of the Rh factor. For example, some people have A positive blood while others have A negative blood, depending on whether the Rh factor is present or absent.

Knowing your blood type is important because it determines which blood types are safe for you to receive and which recipients can safely receive blood that you donate. Blood transfusions must be carefully matched to avoid complications. For example, if you have type A blood, you can safely receive blood from someone with type A or type O blood, but not from someone with type B or AB blood.