The use of information systems in the health care area, specifically in Mobile health care, can result in delivering high quality and efficient patient care. At the same time, using electronic systems for sharing information contributes to some challenges regarding privacy and access control. Despite the importance of this issue, there is a lack of frameworks in this area. In this paper, we propose a trust-based model for information sharing between mobile health care applications. This model consists of two parts, the first part calculates the needed amount of trust for sharing a specific part of information for each user, and the second part calculates the (contextual) current existing amount of trust. A decision for sharing information would be made based on a comparison between the components.To examine the model, we provide different scenarios. Using mathematical analysis, we illustrate how the model works in those scenarios.