This study includes a detailed analysis of subject deployments realized in English and Vietnamese doctor talks at consultations with patients. The focus is to base on doctor's uses of subject to compare interpersonal meanings hidden behind doctors' consultation of the two selected languages. The theoretical framework used in the current study is the mood system of Systemic Functional Linguistics (SFL) which includes four main types of subject: (1) subject explicits, (2) subject implicits, (3) subject interactants, and (4) subject non-interactants (Halliday & Matthiessen, 2004; Vân, 2017). The data was collected by note taking and recording of 120 conversations (60 English conversations downloaded from YouTube; and 60 Vietnamese conversation recorded from real sites of consultation). The purpose of this study not only finds out the similarities and differences of interpersonal meanings hidden behind doctors' uses of subject but also confirms the necessity of change of subject deployments in medical discourse that lead to the movement of patient-centeredness mood.