A reformulation of health economics is proposed that explicitly involves institutions. Decisions regarding health are taken under uncertainty, in the face of which institutions work and allow dealing with it. Taking institutions seriously allows moving forward from the economics of medical care (on which the mainstre am has focused) to a real economics of health; it also allows explaining the growth of health expenditure as the result of the interaction of social institutions. In this approach, the unit of analysis is changed to the rule, rather than the individual agent. The subject of study is the institution.