Hello Chantel and Tigger,
Welcome!
Have you seen this page that talks about your insulin?
viewtopic.php?f=19&t=302
When you first log on to The Main FDMB forum.....There is a category towards the bottom called Insulin Support Groups and it has canninsuln in it so you can also
read other posts from other users specifically on your insulin.
I am not familiar with your insulin either. But we do have a few who are.
Is the Hills diet dry food? That is probably part of the problem. All dry foods are high in carbohydrates even the prescription ones.
What brands are available to you and we can help you find a canned food that would be more beneficial to Tigger.
It is much harder for the insulin to do it's job when Tigger's body is full of carbohydrates.
And it doesn't sound like you are home testing his glucose levels.
This is necessary because it shows you when the dosage is too high and how to correct it or if it is too low.
You have found the right place to get help but you will have to learn a lot , read a lot, and take charge. You may even have to find another vet because many of
them are stuck in their ways and don't want your input.
I think your dosage is probably high and is causing the ketones.
I don't want to tell you to go change the cat's diet because you need to learn everything , especially the home monitoring .
If we change the diet right away and Tigger is still on the high dosage, we could cause a hypo reaction.
If you are willing to start learning and find out if your vet will work with you or not.
Explore the possibility of finding another vet and find out whether or not you have choices in other insulins.
( I know some countries do not have other insulin choices )
http://www.2ndchance.info/diabetescat.htm
www.catinfo.org
explore all the topics on the right side at
http://www.felinediabetes.com/
These links will help you start learning quickly so that you won't have to just follow the vets instructions when you know he isn't really helping your cat.