Physicians should have access to the information they need to provide the most effective health care. Medical knowledge and patient-oriented information is dynamic and expanding rapidly so there is a rising risk of information overload. We investigated the information needs of physicians during treatment of Diabetes mellitus patients, using a combination of interviews, observations, literature research and analysis of recorded medical information in hospitals as part of a methodical triangulation. 446 information items were identified, structured in a set of 9 main categories each, as well as 6 time windows, 10 clinical situations and 68 brief queries. The physician's information needs as identified in this study will now be used to develop sophisticated query tools to efficiently support finding of information in an electronic health record.