Brittle diabetes is rare but imposes huge demands on the Health Service in terms of time and costs. It is almost always due to manipulative behaviour. These ‘nice girls’ behave in a very devious way. It is important to recognise the problem, bring it out in the open and treat it at an early stage. This can avoid numerous unnecessary investigations and admissions, and prevent the development of severe insulin resistance which is very difficult to treat and may lead to death.