Hi there,
What's your cat's name? I'm Shelly; my cat's name is Jersey. As the insulin starts to bring the numbers down, you should definitely see a decrease in thirst and urination.
Can I ask a few more questions?
What insulin were you prescribed? Lantus, Levemir, and Prozinc are some of the best insulins for cats. We don't recommend Humulin, Vetsulin, or Caninsulin. Those are harsh insulins that bring the kitties sugars down quickly and wear off quickly.
What are you feeding your kitty? Low-carb diets are the best for diabetic cats. If you are currently feeding high-carb foods, you need to be really cautious about switching to low-carb foods. We've had members here who switched foods and their cats - pretty much all of a sudden - didn't need insulin anymore. It's important to be testing in case that happens.
That brings me to the next question - are you willing to test blood sugar at home? We really recommend home testing since it's the only way to keep our kitties safe. Most people here buy a human glucose meter from Wal-Mart (the ReliOn brands) and get a blood sample from the ear. It really does sound a lot worse than it actually is. Don't let the sound of it scare you - we have lots of testing tips to help. By testing at home, you will know when a dose is too high - or when it's not enough. You'll be able check your kitty's progress on a day-to-day basis. Although the vet can certainly check glucose levels, cats are often stressed at the vet's office, so the readings aren't very accurate. It is also usually cheaper to test at home rather than taking the kitty to the vet every week or two.
One of the biggest concerns, of course, is hypoglycemia. It will be especially important since you aren't testing at home. Here is a link to more information about the signs of hypoglycemia:
http://www.felinediabetes.com/FDMB/viewtopic.php?f=28&t=15887
Welcome to FDMB!
Shelly