In this collaborative autoethnography, we examine the processes whereby people may reframe their interpretations and understandings of health and illness as a result of new diagnostic information. In so doing, we utilise the first author's experience receiving a conclusive diagnosis of cystic fibrosis after years of misdiagnosis to outline some ways changes in diagnosis facilitate shifts in illness management, the nature of health and illness and the experience of the self in relation to health and medicine. Furthermore, we discuss the ways this case reveals the importance of examining and comparing the social construction and transformation of health and illness within and between different individual and collective lived experiences over time. In closing, we draw out theoretical and empirical implications for understanding transformations in the nature of health and illness over the life course as well as future directions for research investigating shifts in illness management and understanding over time (A virtual abstract of this paper is available to view at: https://www.youtube.com/channel/UC_979cmCmR9rLrKuD7z0ycA).