Hello Jackie and sugarcat Bob, and welcome to FDMB
Has Bob started on insulin yet?
If he hasn't then you may want to bear in mind what Vyktor's Mum wrote above about insulin choices. Are you in the US? If so, then you have several insulin options available to you.
If it is your hope/plan to use sliding scale dosage then you would be better opting for a non-depot insulin like Prozinc or PZI (these are more adaptable when it comes to changing the dose and the time of the shot.)
A lot of kitties actually do very well on fixed doses at fixed times. But others do better with sliding scale dosage. (My own sugarcat has always been on sliding scale dosage.)
To start out though it is important to know how a given dose of insulin works in your cat's body. For example, it's helpful to know what, say, one unit (a typical starting dose) will do, before adjusting upwards/downwards. Also, the blood glucose numbers can be very wonky initially after starting on insulin (as the cat's body learns to use it); so it's helpful to give those inconsistencies a chance to settle out so you can see the clear picture.
It sounds like you're feeding dry food at the moment?
You may find quite a difference in Bob's blood glucose levels once you transition to low carb wet food. And if he isn't on insulin yet then this could be a good time to transition him. For a cat already on insulin we recommend that the diet is only changed to lower carb if the caregiver is comfortable with hometesting and can monitor the effect of the diet change at home (and can reduce the insulin dosage if necessary.)
A diagnosis of feline diabetes can come as quite a shock at first. But the good news is that with a committed caregiver, and a little bit of luck, a diabetic cat can live as long and as happily as a non-diabetic.
Some cats will be on insulin for life, but quite a few lucky cats will go into remission from their diabetes (be able to have their diabetes diet-controlled) either temporarily or permanently.
Welcome aboard!
Eliz