This is indeed one of those frustrating cases. I would stop the pred all together and run fluids to help rehydrate Scoots and to lower his glucose level. As for how much insulin and what type of insulin to use, I use the same guidelines that are used for cats. I start with Ultralente insulin (0.2 Units) per ferret then adjust the amount based on the blood glucose levels. Some use NPH insulin starting at 0.1 units per ferret. These cases are frustrating because it is hard to get the glucose level back into the normal range. One theory as to why these insulinomas ferrets become diabetics is that the tumor is actually a glucagonoma. Again this is a theory that has not been proven, but it does seem logical. Fortunately these cases are rare, but they do happen sometimes. Also this is a case that brewers yeast may help. Good Luck with this one, Jerry Murray, DVM [Sukie note: this is an off-chance that leads some vets to test both glucose levels and insulin levels before some treatments or surgery. One of our's does it. If you check the cross-posts in the archives or the FHL files I believe that an alternative hypothesis for this type of unusual situation is also discussed by Bruce Williams.] [Posted in FML issue 3448]