Health insurance companies in Brazil have their data about claims organized having the view only for service providers. In this way, they lose the view of physicians’ activity and how physicians share patients. Partnership between physicians can be seen as fruitful, when they team up to help a patient, but could represent an issue as well, when a recommendation to visit another physician occurs only because they work in same clinic. This work took place during a short-term project involving a partnership between our lab and a large health insurance company in Brazil. The goal of the project was to provide insights (with business impact) about physicians’ activity from the analysis of the claims database. This work presents one of the outcomes of the project, i.e., a way of modeling the underlying referrals in the social network of physicians resulting from health insurance claims data. The approach considers the flow of patients through the physician–physician network, highlighting connections where referrals between physicians potentially occurred. We present the results from the analysis of a claims database (detailing 18 months of activity) from the health insurance company we partnered with. The main contribution presented in this paper is the model to reveal mutual referrals between physicians. Results show the proposed model reveals underlying characteristics of physicians’ activity from real health insurance claims data with multiple business applications.