How Many Blood Types are There?

If you’re ever asked how many blood types are there, the correct answer is eight. There are four major blood groups, which are defined by what types of protein molecules are present in your red blood cells and blood plasma — the groups are A, B, AB and O. In addition, each of the groups can have either positive or negative classifications, which is determined by whether or not you have Rh factor on your red blood cells. You can find more information here: