Dr. Welch is a general internist and professor of Medicine at the Dartmouth Institute for Health Policy and Clinical Research in the Geisel School of Medicine. He is also a professor of Public Policy at Dartmouth College and a professor of Business Administration at the Amos Tuck School.

For the 25 years he has been practicing medicine, Dr. Welch has been asking hard questions about his profession. His arguments are frequently counter-intuitive, even heretical, yet have regularly appeared in the country's most prestigious medical journals — Annals of Internal Medicine, Journal of the American Medical Association, the New England Journal of Medicine and the Journal of the National Cancer Institute — as well as in op-eds in the Los Angeles Times and the New York Times. His most recent book is Less Medicine, More Health – 7 Assumptions that Drive Too Much Medical Care.

Dr. Welch is very much part of the "Dartmouth School" that questions the assumption that more medical care is always better. His research has focused on the assumption as it relates to diagnosis: that the best strategy to keep people healthy is early diagnosis – and the earlier the better. He has delineated the side-effects of this strategy: physicians test too often, treat too aggressively and tell too many people that they are sick. Much of his work has focused on overdiagnosis in cancer screening: in particular, screening for melanoma, thyroid, lung, breast and prostate cancer.