Other Causes of Hyperglycemia and Glucosuria

Hyperglycemia and glucosuria, especially if transient, can occur for reasons other than DM. Cats are particularly predisposed to epinephrine-induced hyperglycemia, sometimes reaching serum concentrations as high as 22 mmol/L (400 mg/dL). Glucosuria may also be present under these circumstances, depending on time of urine collection and duration of the episode of hyperglycemia. Retesting when the cat is more settled, having the owner collect urine at home, or measuring glycosylated hemoglobin or fructosamine will help differentiate transient hyperglycemia from DM. Glycosylated hemoglobin assesses the blood glucose level over the previous 8-12 weeks, and fructosamine estimates the blood glucose level over the previous 2-3 weeks. Fructosamine testing is more commonly used in animals. In addition to differentiating between transient and long term hyperglycemia, these tests are also useful in assessing glycemic control in patients receiving treatment for DM.

High concentrations of endogenous or exogenous glucocorticoids can elevate blood glucose, though usually not sufficiently high to result in glucosuria. Postprandial blood sampling of monogastric animals is a common cause of mild elevations in blood glucose, however, glucosuria would not be expected. Very ill or moribund cattle often have extremely high blood glucose concentrations, presumably from increased endogenous glucocorticoid and epinephrine release, and from decreased peripheral glucose utilization. Glucosuria without hyperglycemia is discussed in Chapter 7: Renal System.