Our 17 year old orange tabby mix Lucy developed diabetes after a week long stay at the vet for a kidney infection. She was on antibiotics via intravenous feed for the week. She came home and started exhibiting diabetes symptoms (increased urine volume & water consumption) shortly thereafter. That was well over 3 years ago. She has been on Lantus brand glargine insulin. Since then it has been difficult to get to a consistent dose She has gone up and down and then off at least five times. She eats the same high protein wet food diet (specific varieties of Fancy Feast). Her weight is stable. I settled into routine weekly testing at least three hours after eating to track her status either on or off insulin. I add a test if her appetite gets stronger and she want more frequent feedings and she gets daily tests when we are changing or reestablishing dose or when she first goes OTJ. She goes OTJ for between several months and a few weeks, then boom, her glucose is in the upper 100s to lower 200s range. The reintroduction of insulin is a challenge. Her body "resists" the insulin initially, requiring split shots totaling 4-5 units, then usually within a week or so, she drops down to 2-3 units total. She goes back to weekly monitoring and is stable for sometimes several months, then we find we again have to taper till eventually she is back OTJ. Her normal glucose using a Bayer glucose tester is 80-130. The thing we would like to understand is what drives her body the on and off the need for insulin? We are good about her diet and general care. Is there something else that can be driving the on and off conditions?