Coming out of remission?

Hey friends,
So about a year and a half ago I posted about Paxton who was diagnosed with diabetes. After about 2-3 months and converting to a 100% wet food diet and insulin he finally went in to remission. Since then he has been eating strictly twice a day with low carb wet food. In the past few weeks we have had some issues with constipation, and vomiting up his food as if he wasn't digesting it. His blood sugar levels tested at 200 the other night after vomiting his food up. We treated him with some magnesium citrate and the following day his levels were back down to 85~ and he passed all of the hard stool. Today we noticed him acting a bit lethargic and just tested him at ~200 about 4 hours after his dinner. His diet changed about a few months ago once EVO went off the market, but his levels were still okay. On occasion he may lick a spoon in the sink etc, or find a few stray pieces of dry food because he does live with 5 other cats. We keep a close eye on him and we can't really tell of anything out of the ordinary that would be causing his levels to rise..any thoughts you folks can offer?
Thanks

 

How are his teeth? I heard that diabetic cats need cleaning more often, at least once a year. Not sure if that applies to cats in remission, though.