OK that's some good info, no other health issues, not recently diagnosed, but man, that is one huge high starting dose of 5u BID. When was the last increase done? Does your vet do curves or something to determine the increases?
As has been suggested, there's a protocol that most follow around here, and it's worked quite well with many many cats getting off insulin, or getting very regulated.
Here are some links with the info for you - the last one is about shooting lower numbers:
Tight Regulation Protocol
Lantus & Levemir – Insulin Depot –AKA- Storage Shed
Lantus & Levemir – Data Ready to Shoot Low Numbers
If you were able to remove ALL the dry foods, including any treats, you may see a great deal of movement in his dose needed, in the downward direction. That dry food is not referred to as kitty krack for nothing! If one of mine gets just a small mouthful of dry, her numbers will be in the 400s.
Another few links of info you should have handy and even print out if needed is relating to hypo situations. With the change in foods and drop in his insulin needs, you may run into a time when he drops REALLY low:
List of Hypo symptoms
How to treat HYPOS-They can kill! Print this out!
Jojo’s HYPO TOOLKIT
I for sure don't know what others would have to say about his shot for tonite, but I think I'd wait to see where his BG ends up. Did I miss it? What time are his shots? It may be a good idea to post his BG just before his shot time and see what sort of feedback you get.
One thing about food is that most people remove all foods for 2hrs prior to the shot time because food influences the numbers and you want to see a clean number and is not higher because of some food eaten just an hour before.
As for fat, I can totally relate to that! I am trying to figure out how to get my chunky monkey down a few lbs!
I know the others have mentioned insulin resistance, and 10units is what that says to me, but first you need to be sure that food is not the culprit in alot of that dose. For sure the food is important, so let's sort out the food and then see where you are. If he's still up with the higher number, but on all low carb wet food, you may be looking at insulin resistance and can have him tested for those conditions.
That's no problem, so don't worry about that part for now. It is worth mentioning though and keeping in mind.
Here's how we measure the times when we fill out the spreadsheet or even just post the numbers in here.
I'll use one of mine as an example.
6am - tested Oliver and he was 212. I gave him his morning shot of 22units. That's his amps am pre shot BG.
9am - tested him again and he was 206. That's what we call the +3 number or 3 hours after his shot.
If I were to post in here, I'd put the following:
212 - amps
206 -+3
I'll test him again around noon and that will be his +6 BG number
That 113 you got means he's coming up slowly.
His amps (or +12) was ? I am guess you give shots every 12hrs, so this time is his +12 or amps.
His +3 (+15) was 95 (this number is 15hours after his last shot)
His +5 (+17) was 113 (this number is 17hours after his last shot)
I know all the numbers can be confusing, but it sure looks like the food change is making a difference and he has been looking funny because he was likely going too low.
Now that you are here, you are going to be just fine and casanova's going to be even finer.
Keep testing through the day, and then closer to his shot time, you can post and see what is thought about what his shot should be tonite.