Insulinomatosis is a rare cause of hyperinsulinaemic hypoglycaemia. The ideal management approach is not known. A 40-year-old woman with recurrent symptomatic hyperinsulinaemic hypoglycaemia was diagnosed with an insulinoma. A benign 12 mm pancreatic head insulinoma was resected but hypoglycaemia recurred 7 years later. A benign 10 mm pancreatic head insulinoma was then resected but hypoglycaemia recurred within 2 months. Octreotide injections were trialled but exacerbated hypoglycaemia. After a 2-year interval, she underwent total pancreatectomy. A benign 28 mm pancreatic head insulinoma was found alongside insulin-expressing monohormonal endocrine cell clusters (IMECCs) and islet cell hyperplasia, consistent with a diagnosis of insulinomatosis. Hypoglycaemia recurred within 6 weeks. There was no identifiable lesion on MRI pancreas, Ga-68 PET or FDG PET. Diazoxide and everolimus were not tolerated. MEN-1 testing was negative. Insulinomatosis should be suspected in insulinomas with early recurrence or multifocality. De novo lesions can arise throughout the pancreas. Extensive surgery will assist diagnosis but may not provide cure.