Hypoglycemia (low blood sugar) may be seen any time after insulin is given, even in cats that have been well-controlled for years. Signs are usually progressive and may include weakness, wobbly (ataxic) gait, disorientation, vocalizing, apparent blindness, walking in circles, seizures and coma. Death may be imminent. Corn syrup or honey should be rubbed on the gums immediately due to their high sugar content and rapid absorption rate, and the cat should be rushed to the veterinarian for evaluation.

It is particularly important to watch for hypoglycemia whenever a cat is started on insulin, the insulin regiment is changed, or nutritional changes occur, such as loss of appetite or vomiting. Insulin should never be given to a cat that is not eating.