Banting, a farmer's son from Alliston, Ontario, began studying to be a medical missionary at Victoria College, Toronto, in 1910. During his studies he concentrated increasingly on medicine and graduated MD in 1916, whereupon he immediately joined the Canadian Army Medical Corps. In 1918 he was awarded the Military Cross for gallantry in action and was invalided out of the army.

Banting then returned to Toronto and worked for a time studying children's diseases before setting up practice in London, Ontario, in 1920. He also began work at the London Medical School, specializing in studies on the pancreas, particularly the small patches of pancreatic cells known as the islets of Langerhans. Earlier work had shown a connection between the pancreas and diabetes mellitus and Banting wondered if a hormone was produced in the islets of Langerhans that regulated glucose metabolism. In 1921 he approached John MacLeod, professor of physiology at Toronto University, who was initially skeptical. Feeling that Banting needed help in physiological and biochemical methods, Macleod suggested the assistance of a young research student, Charles Best, and eventually merely granted Banting and Best some laboratory space during the vacation, while he went abroad.

Over the next six months Banting and Best devised a series of elegant experiments. They tied off the pancreatic ducts of dogs and made extracts of the islets of Langerhans free from other pancreatic substances. These extracts, called ‘isletin’, were found to have some effect against diabetes in dogs. Prior to trials on humans, Macleod asked a biochemist, James Collip, to purify the extracts and the purification method for what was now known as insulin were patented by Banting, Best, and Collip in 1923. They allowed manufacturers freedom to produce the hormone but required a small royalty to be paid to finance future medical research.

The pharmaceutical firm Eli Lilley began industrial production of insulin in 1923 and in the same year Banting was awarded the chair of medical research at Toronto University and a government annuity of $7000. The Nobel Prize for physiology or medicine was awarded jointly to Banting and Macleod in 1923; Banting was furious that Best had not been included in the award and shared his part of the prize money with him. Macleod shared his portion with Collip. In 1930 the Banting and Best Department was opened at the University of Toronto and Banting became its director. Under Best's guidance, it became the center of medical research in Canada. His own later researches were into cancer and also the function of the adrenal cortex.

Banting was knighted in 1934. When war broke out in 1939 he joined an army medical unit and worked on many committees linking Canadian and British wartime medical research. His bravery was much in evidence at this time, particularly his personal involvement in research into mustard gas and blackout problems experienced by airmen. In 1941 on a flight from Gander, Newfoundland, to Britain his plane crashed and he died in the snow.