I've been in a situation where my housemates thought I needed insulin, when in fact I was having a really bad hypo. I told them right at the beginning of the academic year that I have type 1 diabetes, if I look unwell and I can't assist myself, call for an ambulance and with high blood sugars I can manage myself. They did call for an ambulance but before that they were going through my kit and saying to each other "I think she needs insulin". Because I couldn't talk, I mumbled out a word no or made a sound that sounded like no. So I don't really know if there is a difference between letting people know or not tell them. Most of the time I tell people around me I get questions like "can you eat sugary things?" Like everyone else, I just tell people in case something happens.