AbstractIt has been largely accepted that face-to-face consecutive interpreting should be studied as a communicative event and an interactive process. Linguistic methods, including conversation analysis, have been used to investigate interactive elements in the discourse, such as turn-taking, adjacency pair, overlapping speech, repair, etc. Researchers acknowledge that participants' verbal behaviours in the turn-by-turn interactions are co-constructed by all participants; however, little has been said about the co-constructive mechanism. This research aimed to provide a better understanding of the generic mechanism of such co-construction, hoping to inform the training for interpreters and medical professionals who work with them.Using conversation analysis, I recorded seven naturally occurring interpreter-mediated GP consultations in the UK. Participants included two GPs, three professional and ad hoc interpreters and seven patients speaking either Urdu, Mirpuri Punjabi or Czech.My analysis elaborates on the inter-determination between the types of information the primary speakers (doctor and patient) produce in the current turn and the consequent actions the interpreter undertakes in the next turn, and also points out that such inter-determination is not definite in that the interpreter's turn design is also influenced by their own characteristics. This analysis emphasises that the interpreter, both professional and ad hoc, is key to the quality of the doctor-patient communication and doctors can alter their own behaviours to optimise the interpreter's turn-design and thus the communication outcome.This research provides an insight into the co-construction of the triadic interactions in interpreted medical consultations. With a better understanding of this mechanism, doctors may be taught to alter their verbal behaviours to optimise the interpreter's performance and thus improve their communication with patients. This interactional framework may also help us understand other critical issues of power, identify, cultural competence, etc.