I have heard that having diarrhea can effect your birth control. What I want to know is, how much. Last week we went out to dinner around 7:00 pm and I took my pill at my usual 9:00 pm. At 11:30 pm I had diarrhea when I got home. It was only the one time that night and I was fine again in the morning. Would theh pill have gotten into my system by that time and be okay, or should I be concerned about the effectiveness? I guess I don't know if they mean if you are sick and have diarrhea all day or if that also includes when you just have one instance of it.