Diabetic dog with Cushing's: insulin when starting trilostane
10-year-old spayed female Miniature Schnauzer with diabetes, on porcine lente insulin twice daily at 1.4 U/kg per injection without good control (polyuria, polyphagia and high fructosamine). She has alopecia, a pendulous abdomen and panting. The low-dose dexamethasone suppression test confirms pituitary-dependent hyperadrenocorticism.
You are about to start trilostane. Which approach is correct?
chevron_right Show answer and explanation
A. Increase insulin until controlled, then start treating the Cushing's
While hypercortisolism persists, insulin resistance will prevent control, and a higher dose increases the risk of hypoglycaemia once cortisol starts to fall.
B. Keep the same dose and recheck fructosamine in one month
Waiting a month without monitoring blood glucose is dangerous: insulin sensitivity may improve within days to weeks of starting trilostane.
C. Use mitotane instead of trilostane to avoid worsening the diabetes
There is no reason to prefer mitotane in a diabetic dog. Neither drug worsens diabetes; on the contrary, controlling cortisol improves the response to insulin.
D. Monitor glucose closely and lower insulin as requirements fall
Correct. As cortisol falls, insulin sensitivity improves and requirements may drop markedly, with a risk of hypoglycaemia. Glucose should be monitored frequently (ideally with a continuous glucose monitor), the owner warned about signs of hypoglycaemia, and the dose reduced according to the response.
lightbulb Key takeaway
Hypercortisolism is a common cause of insulin resistance in dogs. Once it is controlled, insulin requirements may fall sharply over the first weeks. Unlike in cats, diabetic remission in dogs is exceptional even when the Cushing's is controlled.
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Updated: November 1, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.