A 28-year-old man with type 1 diabetes uses a continuous subcutaneous insulin infusion. He develops nausea after the pump gives an occlusion alarm; his blood glucose concentration is 15.6 mmol/L and blood ketones are 2.8 mmol/L. He has no fever, is haemodynamically stable and has no alternate source of insulin available through the pump. Which one of the following is the most appropriate immediate action?