One of medicine’s most remarkable therapeutic triumphs was the discovery of insulin in 1921. The drug produced astonishing results, rescuing children and adults from the deadly grip of diabetes. But as Chris Feudtner demonstrates, the subsequent transformation of the disease from a fatal condition into a chronic illness is a story of success tinged with irony, a revealing saga that illuminates the complex human consequences of medical intervention. Bittersweet chronicles this history of diabetes through the compelling perspectives of people who lived with this disease. Drawing on a remarkable body of letters exchanged between patients or their parents and Dr. Elliot P. Joslin and the staff of physicians at his famed Boston clinic, Feudtner examines the experience of living with diabetes across the twentieth century, highlighting changes in treatment and their profound effects on patients’ lives. Although focused on juvenile-onset, or Type 1, diabetes, the themes explored in Bittersweet have implications for our understanding of adult-onset, or Type 2, diabetes, as well as a host of other diseases that, thanks to drugs or medical advances, are being transformed from acute to chronic conditions. Indeed, the tale of diabetes in the post-insulin era provides an ideal opportunity for exploring the larger questions of how medicine changes our lives.