first of all nobody can fire you because you have a medical condition, its against the law. there is no reason you shouldn't say you are diabetic, as long as you keep your levels under check and declare that your medical condition will not effect your work. I had some days that my pump connection was not OK and I had to stay home and fix it. but that happens rarely. if you tend to get highs or lows just make sure u always have some sugar and an insulin pen or even your pump kit for quick replacement and you should be fine.