A 29-year-old woman, with 15 years of poorly controlled type 1 diabetes and established diabetic autonomic diarrhoea, presented with worsening diarrhoea and diabetic ketoacidosis. Frequency of bowel opening was up to 40 times per 24 hours. Octreotide was started, rapidly decreasing bowel motion frequency. Due to previous intolerable side effects of rotten odour breath and flatus, she converted to once-monthly subcutaneous lanreotide (Somatuline Autogel). Her diarrhoea remained controlled without any side effects, until her demise a year later from severe diabetic ketoacidosis. To our knowledge this is the first published report of the successful treatment of intractable diabetic autonomic diarrhoea by once-monthly subcutaneous lanreotide.