A nurse is teaching a school-age child who has type 1 diabetes mellitus and his parents about illness management. Which of the following instructions should the nurse include?

A. While high blood glucose levels are concerning, the threshold for notifying the provider typically starts at 240 mg/dL, especially if ketones are present. However, testing for ketones is the more immediate action during illness. B. Insulin should not be withheld during illness, even if nausea is present, because illness can increase blood glucose levels and the risk of diabetic ketoacidosis. C. Fluids should be encouraged during illness to prevent dehydration, not limited. D. Testing urine for ketones during illness is essential in children with type 1 diabetes, as it helps detect early signs of diabetic ketoacidosis and guide further treatment.