A person's blood type is determined by "the presence or absence of certain antigens – substances that can trigger an immune response if they are foreign to the body," according to American Red Cross.

Most people don’t spare a thought for their blood type unless they’re in need of a transfusion — but could yours hold secrets to your health? There are four main blood types: A, B, AB and O.

Red blood cells are complex — there's much more to blood types than A, B and O. When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works. Many people know ...