The combination of an eating disorder and diabetes mellitus type 1 is a serious double diagnosis. Compensation behavior is often present in the form of insulin restriction which can have debilitating health consequences. Studies on prevalence, diagnosis and mortality are well documented but literature regarding evidence-based treatments is limited. In this article we describe a case study of a patient with diabetes who was admitted to our treatment unit for eating disorders due to manipulation of her diabetes medication. On the basis of this case and a literature study, we conclude that the standard treatment for eating disorders is insufficient for this double diagnosis. An adapted treatment, aimed at both the eating disorder and the diabetes is necessary to increase the chance of recovery.