Headdown, you'd be better off posting this in the Medical Forum here on PPRuNE, and if you do a search in there for "diabetes" you'll find some past discussions on this subject that will most likely answer your question.
I'd normally transfer this up there for you, however I'm going to leave it open in here for a while just in case there are any such CC out there.
All the best,
Sick Squid
Cabin Crew Forum Moderator
PS I'd normally nip in to medical and do a quick search for you to give you an idea of where to go, but am just off to work, so don't have the time right now...sorry.