Blood – everyone's got it. In fact, an adult who weighs between 150 and 180 pounds has around 1.2 to 1.5 gallons of blood in their body. This makes up approximately 10% of an adult’s weight. Blood ...

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.

Blood types are a classification of blood based on the antigens present in red blood cells. In the United States, O-positive is the most common blood type, and AB-negative is the rarest. A blood ...