We present the case of a 77-year-old woman with a medical history of diabetes mellitus type 2 and hypothyroidism who was admitted to hospital after having had episodes of recurrent symptomatic hypoglycaemia. The patient had diabetes mellitus type 2 for 26 years and this had gone into remission over the previous 2 years: she had been having recurrent hypoglycaemia necessitating reduction in insulin doses and then subsequent discontinuation of therapy altogether. There was a history of weight loss, without other red flag features, and the clinical situation was proposed to be secondary to the patients low carbohydrate diet and iatrogenic hyperthyroidism. Several months after insulin therapy had been discontinued the patient was admitted with severe hypoglycaemia. As an inpatient, she was noticeably dependent initially on intravenous dextrose infusions then frequent sugary drinks, with her blood glucose levels plummeting overnight when unable to maintain dietary intake. Supervised fast yielded blood glucose levels of 2.0 mmol/l with an C-peptide level of 2.61 nmol/l (<1.12 nmol/l) and an insulin level of 24.9 mU/l (<13 mU/l). The patient had neuroglycopaenic symptoms at that time which resolved when the blood glucose was corrected. HbA1c was 19 mmol/mol and the urinary sulphonyurea screen was normal. CT imaging revealed a 1.6 cm homogenously enhancing nodule in the tail of the pancreas. Due to the high risk of hypoglycaemia and intolerance of diazoxide therapy the patient underwent enucleation of her pancreatic mass. Pathology confirmed a well differentiated grade 2 Insulinoma. Euglycaemia was achieved for a short period following surgery but reverted to hyperglycaemia as her weight increased. Insulinoma is a rare cause of hypoglycaemia and rarer still in conjunction with diabetes mellitus type 2. We discuss when to reasonably suspect insulinoma in the patient with diabetes, drawing experience from previous case reports.