The communication of a scientific finding as certain or uncertain largely determines whether that information will be translated into practice. In this study, a corpus of 80 articles published in the British Medical Journal for over 167 years (1840–2007) is analysed by focusing on three categories of uncertainty markers, which explicitly reveal a writer’s subjectivity: (1) I/we epistemic verbs; (2) I/we modal verbs; and (3) epistemic non-verbs conveying personal opinions. The quantitative analysis shows their progressive decrease over time, which can be due to several variables, including the evolution of medical knowledge and practice, changes in medical research and within the scientific community, and more stringent guidelines for the scientific writing (regarding types of articles, their structure and rhetorical style).