Postprandial hypoglycaemia is increasingly recognised as a complication of gastric bypass surgery. While post-bypass hypoglycaemia is often responsive to dietary modification, a subset of individuals develop life-threatening neuroglycopenia, with loss of consciousness, seizures and motor vehicle accidents. Such patients require complex nutritional and medical management strategies to reduce postprandial insulin secretion and stabilise glucose excursions, using medications including acarbose, octreotide and diazoxide, and frequent monitoring of glucose values. In an article in this issue of Diabetologia, nationwide registry data from Sweden were used to assess the frequency of severe hypoglycaemia and potentially related diagnoses (e.g. confusion, syncope, seizures, accidental death) following obesity surgery. Relative risk of hypoglycaemia and related diagnoses were two- to sevenfold higher in the post-gastric bypass population, but absolute risk was small. While these data underscore that hypoglycaemia is an important complication of gastric bypass, many questions regarding frequency, pathogenesis and optimal therapy remain unanswered. Given that hypoglycaemia is usually evaluated in the outpatient setting, more precise assessments of hypoglycaemia frequency will require prospective longitudinal studies in post-bypass cohorts. Until such data are available, practitioners should have a higher awareness of symptoms consistent with neuroglycopenia in patients with a history of bariatric surgery. Understanding the beneficial and challenging metabolic consequences of bariatric surgery is a key imperative for the diabetes community, as such data may yield novel insights into mechanisms by which bariatric surgery can lead to diabetes remission.