Re: 3/24 FRED AM=199(.4), +10.5=189
I don't think anyone is quite certain about the physiology of how a kitty goes OTJ, but the gist is that their pancreas is functioning better and can keep up with the glucose without it getting too high. This is in combination with the body's cells using the glucose more efficiently, so it takes less exogenous (external) insulin to get those cells to use the glucose. And then there are some that always need that external insulin. If you have some time, do a search for "glucose toxicity". There are several well-written posts from other members on how high blood glucose (glucose toxicity) causes damage, which in turn makes kitty less able to process the glucose. It's a vicious cycle. Basically, keeping the cat in "normal" or at least below renal threshold numbers is (hopefully) breaking that cycle and allowing all parts of the complex metabolic process to heal.
Some kitties seem to go OTJ rather abruptly, and some take their sweet time and very gradually go down and down in dose until they don't need insulin anymore. Take a look at the sticki'ed thread at the top of the PZI board re: remissions and look over some of the spreadsheets there to see what some of them looked like as they were going OTJ.
After going OTJ, some kitties do tend to run a bit higher than non-diabetic kitties. Dipping into the blue once in a while usually isn't cause for alarm, and a lot of kitties will be in the low 100's before meals. It if becomes more frequent, or goes into the yellows or higher, that's often a sign that they're coming out of remission for any variety of different reasons.