Not sure how others made it to the FDMB, but I first looked at the information on the main page, and the FAQs were one of the first things I read. I recently took another look and realized how out-of-date they are. There are several mentions of how acromegaly is very rare. This point in particular has become inaccurate: Q6.4. My cat has been on insulin for a while and her diabetes is still out of control. Why can’t I regulate her? A6.4. The most common causes for poor control of blood sugar are: Somogyi rebound from too much insulin-- especially if the insulin was started at more than 2 units twice per day, and/or was increased more frequently than 0.5 unit every 7 days. In some cats, rebound occurs at normal or high blood sugar levels, keeping blood glucose levels high all the time. For more on Somogyi rebound, see Gorbzilla's mini-FAQ and Steve & Jock's Wikipedia page. Wrong insulin type for your cat (especially Humulin 70/30 or Humulin N (NPH), which don’t last long enough for many cats). Wrong insulin schedule for your cat (most commonly, shots once per day when the cat needs them twice per day). Not enough insulin -- the insulin dose needs to be increased, slowly and cautiously. Food issues (e.g., constant free feeding on high-carbohydrate food such as Hills W/D or inconsistency in feeding times, amounts and/or types of food) Poor or irregular absorption of insulin (may happen with long-lasting insulins or injections in the scruff) Ongoing infection or inflammatory condition (for example, dental problems, subclinical pancreatitis, or urinary tract infection) which is keeping the blood glucose values high. Other medical issues (such as insulin resistance, acromegaly, and Cushing’s disease / hyperadrenocorticism) may also cause obstacles to regulation. These problems are relatively uncommon, and should not be prime suspects until the more common causes have been ruled out. More details can be found at The Hard-to-Regulate Pet. If a previously regulated cat suddenly starts showing poor response to insulin, two likely reasons are infection and loss of potency of insulin.