Welcome, Amy. Jennifer asked me to stop by since I tend to spend most of my time on the Lantus board. I think she's assuming your vet will be recommending either Lantus or Levemir since both of these insulins have a great track record for getting a newly diagnosed cat into remission. There is a ton of information about Lantus and its use in the starred, sticky notes at the top of the
Lantus board.
I noticed in your other thread you mentioned that Moses had an infection and that's why he was at the vet. It's entirely possible that the infection is what has thrown his blood glucose (BG) levels out of whack. If this is indeed the case, it's very important that you start home testing. I'm assuming that Moses is on an antibiotic? For many cats, if they have an infection or an inflammation, including gingivitis, their BG numbers will go up. Once the problem starts to clear, numbers can come back down. If you're giving insulin, you need to be able to adjust dose as the infection clears out so being able to test is very important.
Are you feeding Royal Canin canned or dry? Most of the Royal Canin canned foods are fairly high in carbs. They range from 4% for the urinary formula to 28% for weight control formula. Royal Canin dry foods are all above 30% carb. A diabetic cat needs to be on a low carb, canned food diet. We consider low carb to be less than 10% carb and most of us feed much less than that.
Janet & Binky's list and this spreadsheet with
pet food nutritional values has information on carb content of most brands of cat food.
Please let us know how we can lend a hand. The people here are very generous with their time and their knowledge. (And I dropped a note to Anne and Liz to let them know you had joined FDMB.)