[header] How to determine positive and negative blood types [title] Understand what determines your rh factor. [step] Located on your red blood cells, the rh factor is a protein you did or did not receive from your parents. You are rh positive when you have the protein. 
If the protein is not present, you are rh negative. [substeps] People with positive rh factors have positive blood types, whether a +, b +, ab +, or o +.