Banting and Best isolate insulin, offering life to millions with diabetes

Story: 1921 C.E.  |  Last updated: July 27, 1921

In a cramped, overheated laboratory at the University of Toronto in the summer of 1921 C.E., two researchers extracted a substance from a dog’s pancreas and changed the course of medicine forever. What Banting and Best pulled from that tissue would transform one of humanity’s most feared diagnoses — a death sentence rewritten as a manageable condition.

Key findings

• Insulin isolation: Frederick Banting and Charles Best successfully extracted the pancreatic secretion now known as insulin in July 1921 C.E., demonstrating it could dramatically lower blood sugar in diabetic dogs.
• Diabetes mortality: Before the discovery, a diagnosis of Type 1 diabetes meant near-certain death, often within months, as no treatment existed to regulate blood glucose in patients whose pancreases had stopped producing the hormone.
• Clinical breakthrough: By January 1922 C.E., the team — joined by biochemist James Collip, who purified the extract — administered insulin to Leonard Thompson, a 14-year-old diabetic boy, in the first successful human treatment.

The road to the pancreas

The science behind insulin isolation did not emerge from nothing. Decades of work across multiple countries had established that the pancreas played a central role in regulating blood sugar. German researchers Paul Langerhans and Oskar Minkowski had each contributed foundational observations in the late 19th century C.E., identifying the islet cells of the pancreas and linking pancreatic removal to diabetes in dogs.

What had eluded scientists was isolation. The digestive enzymes produced by the pancreas kept destroying the very hormone they were trying to extract. Banting’s insight — tying off the pancreatic ducts in dogs so the digestive tissue would atrophy while leaving the insulin-producing islet cells intact — was the key that unlocked it.

He brought the idea to John Macleod, a leading diabetes researcher at Toronto, who gave Banting lab space, ten dogs, and Best, a young graduate student, as his assistant. The two worked through a sweltering Toronto summer with minimal resources. Their persistence, combined with Best’s skill in blood sugar measurement, produced results that surprised even Macleod.

What the isolation meant in practice

The first human patient, Leonard Thompson, received a crude insulin injection in January 1922 C.E. It caused a serious allergic reaction. Collip spent weeks refining the purification process, and the second injection, given just days later, worked. Thompson’s symptoms cleared. He lived another 13 years — not a long life by modern standards, but one that insulin made possible.

The Toronto team moved quickly. Eli Lilly and Company partnered with the university to scale production, making insulin commercially available in the United States by 1923 C.E. That same year, Banting and Macleod were awarded the Nobel Prize in Physiology or Medicine — one of the fastest Nobel recognitions in history for a medical discovery. Banting, infuriated that Best had been excluded, publicly shared his prize money with his collaborator. Macleod shared his with Collip.

The speed of translation from laboratory to patient was remarkable even by today’s standards. Within two years of that summer experiment, pharmacies across North America were dispensing a drug that had not existed before.

Lasting impact

Insulin did not just save individuals — it reshaped what medicine believed it could do. It demonstrated that a hormone could be isolated, purified, and administered therapeutically, opening a path toward the entire field of endocrinology as a clinical practice.

Over the following century, insulin itself evolved. Beef and pork insulins gave way to synthetic human insulin produced through recombinant DNA technology in the 1980s C.E. — itself a landmark moment in biotechnology. Today, long-acting, rapid-acting, and ultra-rapid formulations give patients a level of control that Banting and Best could not have imagined.

Globally, an estimated 422 million people live with diabetes as of recent World Health Organization data, the vast majority of whom depend on insulin or insulin-adjacent therapies to manage their condition. The discovery made in a Toronto summer heat has extended more human lives than almost any single medical intervention in history.

Researchers are now exploring whether insulin production itself can be democratized further. Scientists at the University of Pennsylvania and other institutions have investigated growing insulin in transgenic plants — including lettuce — as a potential low-cost delivery mechanism for low-income countries where injectable insulin remains difficult to access or afford.

Blindspots and limits

The Nobel committee’s decision to overlook Best and Collip remains a documented grievance in the history of science — a reminder that credit in collaborative discovery is rarely distributed fairly. More broadly, while insulin transformed survival for people with Type 1 diabetes, it has never been a cure. The burden of daily management — monitoring blood glucose, calculating doses, navigating supply chains — remains enormous, and insulin access is still unequal across the world, with high costs pricing out patients in dozens of countries even a century after the discovery. The animals used in the research — hundreds of dogs over the course of the Toronto experiments — bore real costs that shaped the eventual outcome.

Read more

For more on this story, see: Penn Today — 100 years of insulin

For more from Good News for Humankind, see:

• Alzheimer’s risk cut in half by drug in landmark prevention trial
• Global suicide rate has fallen by 40% since 1995
• The Good News for Humankind archive on global health

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