Medicine is a science dealing with uncertainty and the art of judging probability. For effective communication, doctors, researchers, or health sciences writers, need to master the use of modality whereby unreal situations can be discussed. How modal verbs -- the most commonly used type of modality applied in the writing of health and medical sciences -- are used in general English can differ from scientific contexts, and within different scientific fields a modal verb may not be used in the same way. This study aims to analyze the use of modal verbs in the abstracts of medical articles published in the past 5 years to enable researchers or medical writers to select the most suitable linguistic devices for their contexts. Modals were discovered to function variously in different parts of medical abstracts, with the highest number in the final part of the abstract structure. In the majority of the abstracts analyzed, usage was found not to be speculation on the part of the author but rather to address the evidence and circumstances. Modals were also found to be context-based and relate to the choices of the tense, voice, reality status, and situation type. The findings can benefit scientific writers and provide EAP, ESP, and EST instructors material for communicative practice.