This study is a corpus-based investigation of how epistemic stance is signaled in medical discourse. In particular, we compiled a discipline-specific corpus of research articles from different fields of medicine ranging from anatomy to endocrinology to explore how particular resources are employed by authors to index their level of (un)certainty towards their propositions. The corpus of the study contained only the results and discussion sections of 100 published medical research articles, totaling approximately 215,000 words. The results of the corpus analyses showed that there was very frequent use of modal auxiliaries by the writers in the field of medicine to express their extra-propositional modality. It was also found that medical researchers did not employ a greater number of boosters to amplify their commitment to the propositions conveyed to the readers. However, the rhetorical uses of boosters were shown to be strategic to portray their higher level of confidence for the sake of credibility and interaction. The findings and implications are discussed with a particular focus on the teaching of writing as a part of English for academic purposes.