Banting first served at Granville Hospital in England before being sent to the front line as a battalion medical officer in June 1918. In late September of that year, Banting was wounded at the battle of Chambrai, where his conduct during the assault earned him the Military Cross. His wound, though not serious, was slow to heal, keeping Banting in hospital until 4 December 1918, more than three weeks after the war had ended. He resumed his duties as a Medical Officer working first in England and, after returning to Canada in the spring of 1919, at the Christie Street Hospital for Veterans in Toronto.

De-mobilized in the summer of 1919, Banting stayed in Toronto an additional year to complete his internship in surgery at the Hospital for Sick Children. In the summer of 1920, having completed his duties as senior house surgeon and intending to set up his own practice as a physician and surgeon, Banting left Toronto for London, Ontario. By the fall of that year a dearth of patients and a lack of funds had driven Banting to the University of Western Ontario where he took a part-time job as demonstrator in the medical school. On the night of 31 October 1920, while taking notes on an article by Moses Barron for an upcoming lecture on the pancreas, Banting conceived the "idea" that would change not only his life but the lives of countless others.

Banting first approached Dr. F.G. Miller, a medical research scientist at the University of Western Ontario. Miller referred Banting to one of the leading specialists on carbohydrate metabolism: Prof. J.J.R. Macleod, then at the University of Toronto. In early November, Banting went to Toronto to meet Prof. Macleod. Although skeptical of Banting's procedure, Macleod arranged for the young surgeon to have laboratory space in the physiology department, dogs, and an assistant. After considering his options in London, Banting returned to Toronto in May 1921 for what was scheduled to be two months of research at the University. He never returned to his London practice.

Although he had assisted Miller with laboratory experiments at the University of Western Ontario, Banting had less experience in that setting than the young assistant J.J.R. Macleod assigned to him before leaving the city for the summer, Charles H. Best. Best had recently graduated from the physiology and biochemistry course and had done laboratory work as part of his degree. Originally the experiments were planned to play to Banting and Best's strengths: Banting was to perform the surgery and Best was to measure the blood and urine sugar levels. Eventually, however, each man became adept at the other's specialty. Observations and calculations from the experiments were recorded in a series of notebooks by both men. The notebooks also document Banting and Best's many difficulties with their experiments that summer: the two-stage pancreatectomy was a lengthy process and many dogs died of infection in the summer heat. But their persistence and hard work paid off when, on 30 July Banting and Best injected diabetic Dog 410 with a pancreatic extract that caused a dramatic reduction in blood sugar levels. Both men enthusiastically described their accomplishment in letters to Macleod and then spent the month of August continuing their experiments on Dog 92.

Macleod returned from his summer in Scotland cautious about Banting and Best's success, but agreed that the experiments should be continued. Although Banting, as a research assistant in the Physiology Department for the summer, had been compensated for work he did that summer, Banting's position was not extended into the academic year. As a result, in early September it appeared that Banting would have no job in Toronto that fall and that any further work he would do on the experiments would be unpaid. In September, Velyien Henderson, head of the Pharmacology Department, offered Banting a position as demonstrator in his department, thus allowing for Banting's work on insulin to continue.

Macleod continued to supervise the insulin research and in November suggested that Banting and Best present their preliminary findings to the Physiological Journal Club of the University of Toronto. Soon after that meeting, Banting and Best began a longevity experiment using Dog 33. The experiment required a continuous supply of insulin, so the two men set about producing a purified extract. In December, Macleod invited J.B.Collip, a biochemist visiting from the University of Alberta, to join the team to help find a purified extract. By Christmas of that year Macleod had sufficient confidence in the work that he suggested that the Toronto team present their findings at the annual meeting of the American Physiological Society in New Haven, Connecticut. On 30 December Banting delivered his first public lecture, entitled "The Beneficial Influences of Certain Pancreatic Extracts on Pancreatic Diabetes," before an audience of prominent scientists, and clinicians including F.M. Allen, E.P. Joslin, and G.H.A. Clowes. Banting's lecturing style was not convincing and the presentation drew many questions from the audience.

The Toronto group, however, was undeterred: in late January Collip's purified extract was successfully administered to the first human patient, Leonard Thompson, and the expertise of the Connaught Antitoxin Laboratories was enlisted to collaborate on the development and production of a pancreatic extract. Banting's involvement in the experimental work is less evident during the winter and spring of 1922. However, he did treat diabetic patients as insulin became more readily available. Sometime in April, with the help of Dr. Joseph Gilchrist and the support of the Department of Soldiers' Civil Re-establishment, Banting established a diabetic clinic at the Christie Street Hospital[13]. Banting also opened his own practice at 160 Bloor Street West, treating private patients, one of whom, Jim Havens of Rochester, N.Y., became the first American citizen to be injected with insulin.

In late May, after an agreement was reached with Eli Lilly & Company to distribute insulin on a larger scale, the research entered the clinical testing phase. Insulin was sent to diabetic clinics in Boston and New Jersey, and in June 1922 the University of Toronto and the Toronto General Hospital established a diabetic clinic under the supervision of Dr. Duncan Graham. Banting was appointed a member of the clinic staff, along with Dr. A.A. Fletcher and Dr. W.R. Campbell . Case studies of these early trials, including some written by Banting, were published in a special issue of the Journal of Metabolic Research.

Meanwhile, Banting began to receive letters from the public requesting insulin treatment. Among the many appeals he received was one from Antoinette Hughes, the wife of the then United States Secretary of State, Charles Evans Hughes. Mrs. Hughes sought treatment for her fourteen year old daughter Elizabeth[15], whom Banting agreed to treat. She arrived in Toronto with her nurse on 16 August 1922, weighing only 45 pounds. A prolific letter writer, Elizabeth recorded many observations of her life under Banting's care that summer and fall. She was also one of Banting's greatest successes; three months after her arrival in Toronto Elizabeth had more than doubled her weight and was able to return home.

As news of the discovery continued to spread, public recognition of Banting's achievement arrived in various forms: in May 1923 the Ontario Legislative Assembly passed the Banting and Best Medical Research Act that established the Banting and Best Chair of Medical Research, for which Banting was appointed the first director ; in July the Dominion Government awarded Banting a lifetime annuity of $7,500; also in July and by this time weary of public speaking, Banting was asked to open the Canadian National Exhibition where he spoke to a crowd of 76,500 people; and on 25 October 1923, Banting became the first Canadian to win a Nobel Prize in Medicine, conferred jointly on Banting and Macleod. The shy, serious farmer's son who wrote his mother every Sunday had become a national hero.

After the discovery of insulin, Banting supervised important research on silicosis but never again had any real success of his own. Although he did complete his M.D. in 1922, Banting did not pursue any advanced degrees. Public confidence in his scientific abilities nevertheless remained high. In 1930 the University of Toronto dedicated a building to him, in 1938 he was invited to become the first chairman of the Associate Committee on Medical Research of the National Research Council, and newspapers continued to print reports of Dr. Banting's new "discoveries" promising that he was working on something even better than insulin.

Banting's personal life was also a matter of public interest. The media reported his whirlwind romance and marriage to Marion Robertson in 1924 and later, after the marriage ended badly eight years later, the media's scrutiny was no less detailed. The press followed Banting on a painting expedition to the Arctic in 1927 with A.Y. Jackson, whom he had met at the Arts and Letters Club in Toronto. In 1934 Banting's name again made headlines: much to his distaste, Banting had been knighted by King George  V. The man who had once written his cousin, F.W. Hipwell, that he liked "the ordinary life" was not able to lead one.

When war broke out again in 1939, Banting, as he had done twenty-five years earlier, was among the first to offer his services to his country. He rejoined the Royal Canadian Army Medical Corps. As part of his war service, Banting was en route to England the night of 20 February 1941 when his plane, a Lockheed Hudson bomber, crashed on the east coast of Newfoundland. Shortly after take-off the plane developed mechanical problems and the pilot, J.C. Mackey, attempted to bring the plane down near Musgrave Harbour, but hit a tree on landing. Both the radio operator and the navigator were killed on impact and Banting was fatally injured. He died the next day.Banting left one son, William, and his second wife, Lady Henrietta Ball Banting.

Books and articles about Banting:

Best, C. H. "Sir Frederick Banting" in University of Toronto Quarterly, Vol. X, No. 3 (April 1941) 

Best, C. H. "Frederick Grant Banting 1891-1941" in Obituary Notices of Fellows of the Royal Society, Volume 4 (November 1942) 

Bliss, Michael. Banting: A Biography. Toronto, Ont.: McClelland and Stewart, 1984 

Collip, J. B. "Recollections of Sir Frederick Banting" in Canadian Medical Association Journal, November 1942