Researchers continue establishing a clear-cut division between identities of doctors and patients, but the perspective of the physician in the event that they became a patient is seldom analyzed. This article shows empirical evidence of the discursive construction of identities and expertise in the accounts of 24 patient-physicians diagnosed and treated for acute or chronic disease in the city of Bogotá, Colombia (2009-2015). An approach to these accounts from Science and Technology Studies, which is a perspective emerged among the field of social sciences during the 1970s that has achieved in our time a broader understanding of expertise, leads to the questioning of stereotypes about who doctors are and who patients are, and to illustrate the difficulty of drawing boundaries between experts and laypeople. Finally, it was concluded that identities and expertise are reconfigured in interaction, in a contingent and situated way, when considering diagnosis and treatment. New meanings of the relationship between doctor and patient were proposed, from a more symmetrical stance.