How common are false negative tests? I'm about a week late on my period (6 days to be exact) and I tested negative. I have really screwed up periods, and I'm trying to just not get my hopes up, AND I know false negatives are not very common, but I was just curious if anyone knew of any solid research about an overall percentage of how common false negatives are. I guess I just want to know so I can move on yet AGAIN.