The growth of interactive technologies has fostered different online health communities (OHCs) where individuals share similar interests in health-related information and exchange social support to facilitate health outcomes. While OHCs offer a variety of benefits to society, it is challenged by surrounding issues of privacy concerns. Breach of privacy poses undesirable consequences for people, and thus privacy concerns can influence individuals' social support behaviour in OHC platforms. Moreover, willingness to engage in the community can be an outcome of prosocial behaviour, motivating people to offer additional social support on OHC platforms. Hence, addressing the role of engagement in a multi-actor online environment requires further attention. Drawing on social support theory, by examining the effects of privacy concerns, control of information, and community engagement, this study develops a framework to create an informed and sharing online community. Using survey data collected from different OHC platforms on Facebook, our study presents some interesting conclusions. Our results show that community engagement and privacy concerns can influence certain types of social support (i.e., information or emotional support), leading to OHC members' intention to participate. Our conceptual model and findings will inform both future research and policymakers.