A 34 year old woman had been diagnosed with type 1 diabetes aged 18 years. She was being treated with twice daily injections of a mixture of short- and intermediate-acting insulins. In general, her glycaemic control had been good, with HbA1c results of 6-8%, a stable insulin requirement and only occasional episodes of hypoglycaemia. She had no evidence of microvascular complications.

At her annual review in the Diabetic Clinic, she reported that over the previous five months, she had been experiencing increasingly frequent episodes of hypoglycaemia, despite having reduced her dose of insulin.