I work with two Type 1 who both test and inject in the office and no one (absolutely no one) has a problem with it. I understand the need to respect others peoples sensitivities and some people are uncomfortable with injections but this is their issue, to be respected, but not your problem. You don't have a problem, you have a medical need. They have the problem, your manager has a problem
you don't have a problem, you aren't a problem. Lots of luck and power educating them so they can see it as it is, tough work but good work.