Despite our understanding that social media and online healthcare communities can help to eliminate health information asymmetry and improve patients’ self‐care engagement, we have yet to understand what happens when patients have access to others’ health data and how patients’ access to these shared experiences and opinions influence their health knowledge and perceived treatment outcome. In this study, we apply social information processing theory and incorporate (1) uncertainty of a treatment, (2) information exposure, and (3) credibility of the information source into patients’ information evaluation function to assess how patients utilize shared health information and experiences. An empirical model, which combines various aspects of patients’ firsthand experiences about treatments into a single construct, yields empirical evidence that patients’ perceived treatment outcome is prone to social influence from other patients’ shared experiences. By disaggregating the sources of social influence, we find that social influence created by generalized others in the community outweighs that by familiar others of one's intimate social group. In addition, we find that other factors, such as positive sentiment in comments and patients’ prior experiences, also affect patients’ perceived treatment outcome. Based on our findings, implications for health promotion and health behaviors are presented.