Orion Systems International Limited has recognised the need in the healthcare industry for an application to provide robust clinical decision support. One possible approach is to develop a case-based reasoner to support decisions made in the disease management process. We have undertaken a project to investigate the validity of using case-based reasoning for this task, specifically focusing on the management of treatment of diabetes patients. An application that uses case-based reasoning has been developed and tested. This paper describes the pre-processing of cases, the development of a case representation and similarity metrics and evaluation. Results show that casebased reasoning could be a valid approach, but more investigation is needed.