© 2019 Elsevier Ltd Privacy amid rapid digitalization of medical records is a critical ingredient to the success of electronic-based health service. This paper explores the potential roles of privacy attitudes concerning medical data, based on a large set of a national sample data (n = 2638) from the U.S. Health Information National Trend Survey. We examine the ways in which privacy concern and confidence are (a) mediated through one's interest in sharing information with health professionals and (b) moderated by one's medical condition and the reliance on Internet. Evidence from this study provides insights into the factors shaping health-related engagement in information technologies, helping us argue that privacy is a key predictor. Discussion offers interpretations of how people's perceived need of medical data will mediate privacy concern, contextualizing the affordances of health technologies in future algorithmic applications.