In 1922, an unlikely team of researchers in Toronto made one of the most important medical breakthroughs of the century: insulin. Their discovery seemed miraculous. When it was given to diabetic patients on the brink of death, their condition rapidly improved. Those present could barely believe their eyes: they had witnessed resurrection. However, this was no simple cure. Injections must be taken for life. Without them, symptoms quickly return, often with fatal results. But while a lifetime on insulin poses great challenges, it also offers opportunities. In this revelatory history, Stuart Bradwel looks back on one of medicine's most celebrated innovations. Setting professional narrative against subjective patient experience, he tells the story of a drug that has challenged many of the basic assumptions upon which medical practice is built, both inside and outside the clinic. Nevertheless, Bradwel reminds us that the centenary of this apparent "wonder drug" should be no cause for celebration. Insulin often remains inaccessible to those who need it most: elusive prescriptions, uneven availability and sky-high prices result in rationing and desperate do-it-yourself research and development. In the face of bootstraps rhetoric and "Pharma Bro" capitalists, patients across the world are left to fend for themselves. There is a long way to go in the twenty-first century until insulin truly fulfils the extraordinary promises made by its discovery.