Practice question

A 45-year-old man is admitted with diabetic ketoacidosis (DKA). His blood glucose is 28 mmol/L, pH 7.15, and bicarbonate 12 mmol/L. He is started on a fixed-rate intravenous insulin infusion (FRIII) at 0.1 units/kg/hour and IV fluids. Four hours later, his blood glucose has fallen to 13 mmol/L, but his ketones are still 4.0 mmol/L. What is the most appropriate next step in management?