You are seeing a 30-year-old female in A&E who has presented with persistent vomiting. This patient is also complaining that they feel very thirsty and that she has abdominal pain and diarrhoea. The patient also informs you that she has lost a lot of weight in the past few days. When speaking to the patient you notice a fruity smell on their breath. Given the diagnosis, what is the most appropriate next step in this patient’s management?