You are welcome! Yes that is DEFINITELY safe now that you switched him so suddenly. A cat on insulin switched to a low-carb diet will need less insulin, so maintaining the dose is dangerous. Thank you for reducing.
Okay. So, you DO need to tackle that dental. Lots of things increase insulin needs. We had a kitty here recently whose owner thought he was knocked out of remission because his BG was going up - turns out he had some bad teeth, and she's getting it corrected. We want to eliminate all things that cause BG to be high - stress, high-carb food, bad teeth, infection/illness. Added to that, diabetics NEED to eat. If his teeth hurt too much to eat you're going to have issues giving him shots.
Wellness Core I believe is suitable for diabetics. Canidae is a little on the high side, minus the Under The Sun variations. Not sure about Meow Mix.
Here is a chart we use for picking out food - it's extensive, but just look at the carb amounts. Anything under 10% (ideally under 5%) is good for diabetics. There are cheap options if price is an issue.
Are you in the US? If so go to Walmart and purchase a ReliOn Prime, it is the cheapest meter + strips available. $9 for the meter, $18 for 100 strips.
Here is a link to learning how to test for when you're ready! It's got a learning curve in the beginning but don't worry, everyone here can do them in their sleep now, it becomes second nature. I recommend getting your kitty (what's his name?) some treats to get him used to testing. Baked chicken or PureBites treats are popular. I think they sell PureBites at Petsmart too.
Here's a shopping list for testing, to make it easier on you:
ReliOn Prime meter - $9
ReliOn Prime testing strips - $18 for 100
ReliOn Lancets 26 Gauge - $1-2 for 100
ReliOn Lancing Device - $5 (optional, some people prefer to poke freehand)
Travel-sized Vaseline - $1
Neosporin Ointment + Pain Relief (NOT the cream) - $5
Cotton Pads - $2 (optional - you can use a homemade rice sock instead)
Ketostix - $7
I also would like to see you prepare a "
Hypo Kit". This is to prepare you in the event that your cat experiences low numbers. You can keep him safe if you are well-stocked!
Karo Syrup - $3
A few single cans of Fancy Feast Grilled OR Sliced OR Marinated in Gravy - $.60 each (these are your medium-carb cans)
A few single cans of Fancy Feast Medleys Tuscany OR Medleys in Gravy or Broth OR Gravy Lovers Gourmet Beef Feast in Gravy - $.60 each (these are your high-carb cans)