This is supposed to be a good site for diabetes; there is also a message
board on there too:

http://www.felinediabetes.com/

my cat Em has been diabetic for 7 years now.  She is on twice daily
injections since she was diagnosed.

One thing you will seriously want to consider is changing your cat's diet
over to a catkins type.  High protein and fat, LOW carb.

Em was on extremely high doses of insulin for years seven units BID.  When I
found out about catkins and what it can do for diabetics, I switched her
over (monitoring closely at home with a glucometer - standard one that human
diabetics use) and her insulin need was greatly reduced.  When she was  on a
zero carb - raw diet (I made at home) I was over dosing her at every turn
with insulin. Giving less than half a unit was impossible.  Was about to
take her off it completely when she decided she didn't want to eat raw any
more.  So now we are on one of the lowest carb foods I can find.  Her
insulin need is about half a unit.. Im still fine tuning due to other health
issues.

But I tell you this story to tell you how extremely important it is to
switch off dry food, or even canned food with high carbs and wheat gluten.
The felinediabetes.com website has a lot of info regarding food choices.

Good luck!!