Objectives <p>Online medical choice behaviour in online health communities represents a key step in converting online consultation services. Understanding its influencing mechanisms offers practical value for improving user experience and platform operations. Prior studies mainly examined single information elements and lacked a systematic analysis of multiple information-processing routes and their mechanisms.</p> Methods <p>We used data from 313 physicians in the psychiatry and psychology department of an online health community (Haodf.com) in China. Guided by the Elaboration Likelihood Model and trust theory, we built regression models incorporating the central route (content quality and interaction quality) and the peripheral route (reputation credibility, professional competence credibility, and service capability credibility). We tested the effects of these information factors on patients’ online trust and online medical choice behaviour, and further examined the moderating roles of user involvement and consultation price.</p> Results <p>Content quality, interaction quality in the central route, and reputation and service capability credibility in the peripheral route significantly enhanced patients’ online trust. Online trust, in turn, significantly positively affected online medical choice behaviour. Moreover, higher user involvement strengthened the impact of central route factors on online trust, while higher consultation price weakened the positive effect of online trust on online medical choice behaviour.</p> Conclusions <p>This study demonstrates the differentiated roles of multiple information-processing routes in shaping trust and behavioural transformation in online health communities. The findings provide empirical evidence to support optimised interface design and differentiated service strategies for online consultation platforms.</p>