Insulin was discovered in 1921 at the University of Toronto by a team that included the surgeon Frederick Banting, the medical student Charles Best, the physiology professor J.J.R. Macleod, and the biochemist James Collip. Their work took a previously unstoppable disease — type 1 diabetes — and turned it into a manageable chronic condition. The 1923 Nobel Prize in Physiology or Medicine was awarded to Banting and Macleod, though Banting and Macleod each voluntarily shared their prize money with Best and Collip.
Before 1921: Life With Type 1 Diabetes
Without insulin, a diagnosis of type 1 diabetes was effectively fatal. The only treatment was the “starvation diet” developed by Frederick Allen, which extended life by weeks to months by reducing the carbohydrate load the pancreas could no longer handle — but it left patients severely malnourished and still eventually led to ketoacidosis. Pediatric wards of the early 20th century were full of children wasting away; most did not live a year past diagnosis.
The Toronto Team
| Person | Role | Contribution |
|---|---|---|
| Frederick Banting | Orthopedic surgeon with a research idea | Conceived the experimental approach; led the dog experiments |
| Charles Best | Medical student (summer assistant) | Performed the dog experiments with Banting; measured blood sugar |
| J.J.R. Macleod | Professor of Physiology, University of Toronto | Provided laboratory space, animals, and scientific oversight |
| James Collip | Visiting biochemist | Purified the pancreatic extract so it was safe to give to humans |
The Key Experiments (Summer 1921)
Banting’s original idea was to tie off the pancreatic ducts of dogs, causing the digestive-enzyme parts of the pancreas to atrophy while leaving the islets of Langerhans (which produce insulin) intact. Extracts from these atrophied pancreases, he reasoned, would contain the hormone without enzyme contamination.
Over the summer of 1921, Banting and Best performed these experiments. They extracted pancreatic tissue, injected it into diabetic dogs whose own pancreases had been surgically removed, and measured a dramatic fall in blood sugar. One of those dogs, named Marjorie, became the first animal whose life was extended by exogenous insulin.
The First Human Treatment (January 1922)
On January 11, 1922, 14-year-old Leonard Thompson, near death from diabetic ketoacidosis at Toronto General Hospital, received the first human injection of the Banting-Best extract. It produced only a modest glucose drop and caused an abscess at the injection site — Collip’s purification work was not yet complete. Twelve days later, a purer extract prepared by Collip produced rapid and dramatic improvement: Thompson’s blood sugar fell to near-normal, his ketones cleared, and he regained strength. He lived 13 more years on insulin before dying of pneumonia at age 27.
The 1923 Nobel Prize and the Controversy
The Nobel Committee awarded the 1923 Prize in Physiology or Medicine to Banting (as the originator of the idea) and Macleod (as the senior scientist whose lab made it possible). Banting was publicly angered by the omission of Best, his direct collaborator, and announced he would split his prize money equally with him. Macleod, in turn, shared his prize money with Collip, whose purification work had been critical.
The controversy has shaped how the discovery is taught ever since. Today most accounts name all four contributors, though the original Nobel citation does not.
The One-Dollar Patent
In 1923 Banting, Best, and Collip assigned the insulin patent to the University of Toronto for a nominal one dollar. Banting famously argued, “Insulin does not belong to me. It belongs to the world.” The university licensed production widely — initially to Eli Lilly in the United States and to Connaught Laboratories in Canada — which allowed insulin to scale internationally within a few years. This public-spirited decision shaped the drug’s early affordability.
Who Actually Discovered Insulin First?
Several earlier researchers came close:
- Oskar Minkowski and Joseph von Mering (1889) — showed that removing a dog’s pancreas caused diabetes, establishing that the pancreas made something necessary for glucose control.
- Edward Sharpey-Schafer (1910s) — hypothesized that the pancreas secreted a substance he named “insuline.”
- Nicolae Paulescu (1916–1921) — a Romanian physiologist who extracted “pancreine” from pancreatic tissue and demonstrated its glucose-lowering effect in dogs; his published priority claims were acknowledged by Banting himself.
- Israel Kleiner and Ernst Scott (early 1920s) — produced similar extracts in the United States but did not pursue clinical application.
The Toronto team gets credit because they produced a reliably purified extract and brought it to human patients, not because they were the first to imagine the hormone.
From 1921 to Modern Insulin
| Era | Insulin | Advance |
|---|---|---|
| 1922 | Beef and pork pancreatic extract | First human therapy |
| 1940s | Protamine zinc insulin (PZI) | Longer duration |
| 1950s | NPH insulin | Intermediate-acting |
| 1978 | Recombinant human insulin | First genetically engineered drug in humans |
| 1996 | Lispro (Humalog) | First rapid-acting analog |
| 2000s | Glargine, detemir, degludec | Long-acting basal analogs |
| 2010s | Biosimilar insulins | Cost reduction |
| Today | Ultra-rapid, concentrated, and combination products | Closed-loop pump integration |
Why the Discovery Still Matters
Insulin transformed diabetes from a fatal illness to a manageable condition. It also established several principles that shape modern medicine: that internal-secretion hormones could be extracted and administered; that academic institutions could shepherd patents for public benefit; and that multi-disciplinary teams (surgeon, student, physiologist, biochemist) drive major breakthroughs. Modern therapies — GLP-1 receptor agonists, SGLT2 inhibitors, continuous glucose monitors — still work alongside insulin as the foundation of care. Our treatment hub surveys how these pieces fit together, and our guide on reversing prediabetes covers the preventive side of the same story.
The Bottom Line
Insulin was discovered in 1921 by the Toronto team of Banting, Best, Macleod, and Collip. The first successful human treatment came in January 1922, the 1923 Nobel Prize recognized two of the four, and the patent was handed to the University of Toronto for a single dollar so the drug could reach the world. A century later, insulin remains one of the most important and most studied molecules in medicine — not a cure for diabetes, but the reason millions of people live long lives with it.
