Abstract This article examines the ways in which, in the last centuries of the Middle Ages, the emergence of a literature aimed at preserving health by means of dietary rules or advice establishes a connection between the physician’s authority in matters of health and the capacity of patients and readers to take care of themselves when they are in good health. Born at the same time of social demand and medical necessity (the latter due to the dangers and uncertainties of therapeutic practice), these regimina sanitatis disseminate to a literate public the principles of good hygiene. Some regimina are even adapted to the singularity of a given individual. But the agency of readers, characterized by their capacity for choice and deliberation, also clashes with the claim that a medical authority is necessary for the governance of health.