Abstract We hypothesize that hypoglycaemia in insulin-treated diabetic patients may result from gastric emptying abnormalities causing insulin and food absorption mismatching. We tested gastric emptying in insulin-treated diabetic patients with unexplained hypoglycaemia and without dyspepsia and in diabetic patients without hypoglycaemia, prospectively. Thirty-one diabetic patients with unexplained hypoglycaemic events within 2 h of insulin injection and 18 insulin-treated diabetic patients without hypoglycaemic events underwent gastric emptying breath tests, glycaemic control and autonomic nerve function. Gastric emptying tests were abnormal in 26 (83.9%) and in four (22.2%) patients with and without hypoglycaemia, respectively (P < 0.001). Gastric emptying was significantly slower in hypoglycaemic diabetic patients (t1/2 139.9 ± 74.1 vs 77.8 ± 23.3 and tlag 95.8 ± 80.3 vs 32.84 ± 16.95 min, P < 0.001 for both comparisons; t-tests). A significant association between hypoglycaemic patients and abnormal values of t1/2 and tlag was found (P < 0.001). Gastric emptying abnormalities were more frequent in hypoglycaemic patients. We suggest gastric emptying tests for diabetic patients with unexplained hypoglycaemic events.