You might want to print this page out and carry it with you on the not-so-off chance that you come across an over-zealous screener:

Travelers with Diabetes

I would urge also that you refuse to remove your shoes because of your medical condition. You pick up bugs on your socks while standing on those filthy floors and then transfer those bugs to a nice warm moist environment where they can thrive and multiply when you put your shoes back on.