The fuzzy set concept was introduced by Lotfi A. Zadeh in 1965 to provide a tool to describe vague predicates or classes with imprecise boundaries and which enable an uncertainty nonadditive calculation, based on soft operators. Zadeh recognises that conventional quantitative techniques of systems analysis are intrinsically inappropriate to address humanistic systems. The medical field is appropriate to apply the fuzzy set theory, as vague predicates and subjectivity are an important part of it. In this paper, the fuzzy set concept is used to provide a more flexible definition of certain parameters which state an individual’s health condition, and which will allow to formulate a diagnosis model for the risk of suffering a certain disease, and it is characterized as a case of cardiovascular risk. This model is applied to the development of an expansion strategy for a private health insurance company, which considers sustainability of the healthcare system.