My beloved cat had diabetes (and many other health challenges - he could overcome all of them except a brain tumor, and he fought that one pretty damn well until he was almost 20).
My best suggestion - and I URGE you to check it out, it can be a life saver - is to check out
Feline Diabetes - and join their message board community. There are thousands of people there all dealing with feline diabetes (FD), plus vets and vet techs, and the wealth of information and caring there is absolutely astounding. They will welcome you with open arms, give you all the information you need and give you feedback on whatever the doctors tell you - you'll find tons of help on how diet and other stuff can help - and if you ever run into a crisis with your cat, there are members there 24/7 who can help, walk you through whatever needs to be done, tell you if the cat needs emergency treatment or what else you can do.
In a nutshell, even though caring for diabetic cats is relatively easy once you get used to it --- I'm not sure I would have survived without the people there.
PLEASE check it out and join the messageboards --- I can't urge you strongly enough to do it asap. It will change your life in terms of living with and dealing with FD.