What is Rh negative blood? In short: Being Rh negative means that you test negative for the presence of the D antigen of the Rh blood group system. Here is the longer version: What is the Rh blood group system? The Rh blood group system is a human blood group system. It contains proteins on the surface of red blood cells. It is the second most important blood group system, after the ABO blood group system. What does “Rh Negative” refer to? The Rh blood group system consists of 49 defined blood group antigens, among which the five antigens D, C, c, E, and e are the most important. There is no d antigen. Rh(D) status of an individual is … Continue reading What is Rh negative blood?