@Sarah69 the information bit on your page says you're a HCA, so presumably you work in a hospital or a care home? I can't see either location having any issue with you injecting in the staff room /canteen. There's no need to inject in the toilet. Do you have your blood sugar testing kit and insulin with you as you're moving about at work?
I mean, I usually just inject half an hour before I start my lunch break, so the break starts and then I'm ready to eat. But my work environment involves sitting at my desk. I can see that might be a bit more difficult to do if you are on your feet, don't have all your kit with you and your with patients. If you are not on a break does that mean you can't have a 5 min break if you need a wee? If you're allowed a loo break, you can probably inject in half the time you'd take to have a pee. So you could pause to inject 20-30 min before you're lunch break is scheduled and then you are ready to eat when the break starts. But, obviously, that is rather dependant on the break starting at exactly the time it is scheduled to start, and I'm not sure that's an especially realistic expectation in a care setting.
Your signature says you are on byetta, metformin and lantus. None of these medications need to be talked half an hour before eating, so far as I'm aware. What exactly is it you've been told to inject 15-30 minutes before eating?