An overview of blood types

Most people know what their blood type is, but most people have no clue what a blood type means, or what the differences are between the various blood types. A cursory knowledge just tells you that there is some difference between various types of blood, and that difference is the reason why some blood is incompatible with a person of a different blood type.

A breakdown of blood types
There are four blood types:

  1. Type A
  2. Type B
  3. Type AB
  4. Type O

The difference between blood types comes down to the rate and presence of certain proteins in the blood, which are called antigens, and they are connected to the red blood cells. This typing system is the most common system used in the world, and is referred to as the ABO blood typing system. Most blood types are passed down through the genes from a person’s parents, so most families and the members in the family all have the same blood type- although this is not always the case in some rare circumstances.

How the blood typing test works
Once a person’s blood is drawn from their vein, the blood is put into a test tube and mixed with certain antibodies. The antibodies are specifically chosen to work against Type A and Type B blood. Once the mixing of the antibodies and the blood is finished, a doctor will check to see if some of the blood cells connected with each other. If that is the case, then that means the blood reacted to one of the antibodies (the Type A or Type B ones.) Next is the step known as back typing, in which the serum of the blood is tested against a Type A and a Type B blood sample from another person. If the antibodies match, it determines what blood type it is. Type O blood does not react to either of the Type A or Type B antibodies. The other step when typing blood is to test for the rh factor. If a person’s blood tests rh positive as well as Type A, then that person’s complete blood type would be Type A (positive.) Likewise, if a person tests as rh negative, that would mean their blood type is negative, as well as one of the ABO types.

What blood type really means
Most people will have no use for blood type, until they either give or receive a blood transplant, or donate or receive an organ transplant of some kind.

  • Type A can only give or receive blood and organs to or from people with either Type A or Type O.
  • Type B can only give or receive blood and organs to or from people with either Type B or Type O.
  • Type AB can receive all types.
  • Type O can only receive Type O.

Dave is a freelance writer who specializes in health and medicine articles. His work can be seen at