The relationship between eating disorders and diabetes is complex in terms of both reciprocity and comorbidity. In some cases, patients with eating disorders and diabetes develop 'purging' behaviours through the use of insulin as a bodyweight control tool, with serious physical complications that can compared to those of untreated diabetes (diabulimia). The clinical cases presented have in common the distorted use of insulin: one patient failed to take the required amounts of insulin, incurring hyperglycaemia, while the other overused it, incurring hypoglycaemia. From a psychopathological point of view, both patients were diagnosed with Borderline Personality Disorder. While these are just two case reports, it is our clinical experience that female diabetic patients with eating disorders who use insulin as a tool for weight control (purging) following binge eating should be assessed for borderline personality disorder in order to tailor a more effective therapeutic approach.