Living labs are a relatively new instrument in enhancing open innovation. They are practical environments for innovation aiming at a better mix and match between stakeholders for co-development and reduction of time-to-market of innovations through early involvement of user groups. Living lab settings range from delimited environments for co-creation and development, like a city quarter, a hospital and university campus, to local and regional networks and platforms of open innovation. Participants in living labs are typically universities, research institutes, user groups, small and large firms, non-profit institutions and local/regional authorities. Accordingly, living labs find themselves in a dynamic multi-actor situation that needs to be dealt with, both in their design and management. The focus of this paper is on living labs for health care innovations. Health care is under pressure as a consequence of the aging population, and fast increasing population with chronic conditions and shortage of resource. The paper identifies critical factors in the design of medical living labs using the literature and an analysis of five case studies of such living labs.