Insulin at 1 unit/cat (0.2 units/kg) is an appropriate starting dose; however, the expected response in glycemic control is typically minimal.20 Thus, the dose of insulin should be adjusted in an incremental manner,20,24 with repeat diagnostic testing based on clinical response.
Three weeks following initiation of therapy is a reasonable time to recheck a newly diagnosed diabetic. In general, protocols vary from weekly diabetic rechecks and insulin adjustments to less frequent rechecks occurring every couple of weeks.20,24 To date, there is no consensus on the best interval for diabetic rechecks in the immediate postdiagnosis period. Rather, this is better determined by individual patient status.
Fructosamine, a glycosylated protein in the bloodstream, gives an average of the glycemic control over the previous 1 to 3 weeks.20,24 Various patient-dependent factors are responsible for the window in which fructosamine is representative. Therefore, in a relatively stable patient such as this cat, the 3-week recheck would be appropriate and a reasonable time to make treatment adjustments. Serum fructosamine concentrations and blood glucose curves provide complementary information and can be used jointly to monitor diabetics if needed. Fructosamine findings alone, however, cannot be used to determine whether a Somogyi effect (rebound hyperglycemic response) is occurring.24 Further blood glucose monitoring would be needed.
At the initial recheck, there is insufficient information to determine whether the insulin used is ineffective. This cat was placed on an appropriately low starting dose. However, in many cats, this starting dose is too low to achieve adequate control. A majority of cats are controlled with doses of 0.5 to 6 units/cat.20 A low starting dose is used as it provides a lower risk for hypoglycemic events, which may be common and potentially life-threatening.24-25 Then the dose can be incrementally increased in a slow, methodical manner until control is achieved or the dose reaches a point where insulin resistance is a concern based on the insulin dose and concurrent lack of response. As the insulin dose approaches the higher end of the range most cat’s are controlled within, the clinicians suspicion of insulin resistance should increase. In conclusion, higher doses of insulin should be attempted in this scenario before deeming the insulin ineffective. Regardless, if any concern about insulin effectiveness arises, it is important to review the basics of diabetic management with the owners, including insulin storage, administration, and general management before proceeding with changing insulins and recommending further diagnostic testing.