For all veterinarians. I have a diabetic male cat 12 years old?

his BG today is only 112 he has been steadily coming down again ( for the second time in 9 months) I started giving him insulin last August,6 units twice a day, then down to 4 units, and then down to 2 units twice a day as his Blood glucose started to go back to normal, his BG went back to normal and My vet suggested I stop the insulin shots. My kitty recently showed signs again of high BG so back on to insulin, he has been doing the same thing again and tonight his BG is only 112. Last time it went that low and I gave him 2 units of insulin it dropped to only 21. I have NOT given him any insulin this time. do you think this is ok?