# Insulin Discovery: The 1923 Nobel Prize Rivalry

*Science & Technology · Priya Nair · 2026-09-28*

## TL;DR

In 1923, Frederick Banting and John Macleod received the Nobel Prize for the insulin discovery at the University of Toronto. Banting was outraged that Macleod, who oversaw the lab but did little hands-on work, shared the award. He gave half his prize money to Charles Best, his young assistant.

## Key facts

- Frederick Banting and John Macleod were awarded the 1923 Nobel Prize in Physiology or Medicine for the discovery of insulin.
- Banting was furious that Macleod was included, believing the professor's role in the lab work was minimal.
- Banting shared his prize money with Charles Best, while Macleod shared his with James Collip.
- Leonard Thompson received the first successful insulin injection in 1922 at a Toronto hospital.
- Before insulin, a diabetes diagnosis was effectively a death sentence, with patients surviving only months on starvation diets.

## The Phone Call That Made Banting Furious

In October 1923, Frederick Banting, the Canadian surgeon whose name had become inseparable from the insulin discovery, picked up a ringing telephone and heard a friend's voice on the other end. As the account goes, the friend asked whether Banting had seen that morning's newspapers. When Banting said no, the friend delivered the news himself: he had been awarded the Nobel Prize.

Banting's reply was not gratitude. He told his friend to go to hell and slammed the phone down. Then he walked outside, bought the morning paper, and read the headlines in black and white. The worst thing he could imagine had come true. Yes, he had won the Nobel Prize. But the award had been given jointly to him and to his boss, John Macleod, Professor of Physiology at the University of Toronto.

That joint award is a matter of record. The 1923 Nobel Prize in Physiology or Medicine went to Frederick Banting and John Macleod together, for the discovery of insulin. Macleod had provided the laboratory facilities at the University of Toronto where the research took place. To the Nobel committee, that counted. To Banting, it did not.

He was furious. He believed Macleod had no real claim to the discovery at all. Sharing the prize with him was not merely an injustice in Banting's eyes. It was an insult.

This is a story of enormous egos, poisonous career rivalries, and unfairness. But there is another important character in this drama: diabetes itself.

The word "diabetes" takes its name from an Ancient Greek word meaning "to flow through," a reference to one of the disease's most common symptoms. In the 17th century, the English doctor Thomas Willis reportedly described the illness in a far more memorable phrase, calling it the "urine disease," though that description is not reliably confirmed. In any case, frequent trips to the bathroom were the mildest of the problems patients faced.

Before insulin, a diagnosis of type 1 diabetes meant certain death. Patients could not metabolize the sugar in the carbohydrates they ate. They grew thinner and weaker, and because their bodies produced toxic substances called ketones, they eventually slipped into a coma and died.

Even in the early 20th century, doctors had almost nothing to offer. At most, they could put patients on starvation diets that slowed the disease for a short while. So the discovery of a hormone that could bring high blood sugar down to healthy levels, and even pull patients back from a coma, struck doctors deeply. Because this substance is produced in small, island-like clusters of tissue in the pancreas, it took its name from the Latin word for "island": insulin.

The newspapers announced insulin as a miracle. Praise poured onto Banting. Then came the Nobel Prize. And then came the rage.

## Before Insulin, Type 1 Diabetes Was a Death Sentence

The word itself carries the story. "Diabetes" traces back to an Ancient Greek term meaning "to flow through," a nod to the relentless urination that marked the disease long before anyone understood what was happening inside the body. That constant thirst, that endless march to the bathroom, turned out to be the mildest of the symptoms.

In 17th-century England, the physician Thomas Willis was said to have described the condition as the "urine disease," though that label is not reliably confirmed. It was a blunt, memorable phrase for something doctors could name but could not touch. And for the people living with it, the real horror was still to come.

Before the discovery of insulin, a diagnosis of type 1 diabetes meant certain death. That is not an exaggeration. Patients could not metabolize the sugar from the carbohydrates they ate. So they wasted away, losing weight and strength week by week. Their bodies, unable to use that sugar, produced toxic substances called ketones. Those ketones built up until the patient slipped into a coma and died. For a child, the whole decline could unfold in months.

### What Doctors Could Actually Do

Even in the early 20th century, the cupboard was almost bare. The only real tool doctors had was the starvation diet. They would cut a patient's food down to the barest minimum, sometimes just enough to keep them breathing. It bought time, but only a little. It slowed the disease's march without ever stopping it. The patient still died. Everyone in that room knew it.

So imagine what it meant when researchers finally isolated a hormone that could pull sugar out of the blood and bring it down to healthy levels. A substance that could even wake a patient from a diabetic coma. It was produced in tiny, island-like clusters of cells in the pancreas. When scientists named it, they reached for the Latin word *insula*, meaning "island." That is where the word insulin comes from.

Newspapers called it a miracle. Praise poured in. And behind all of it, a prize fight was already brewing over who deserved the credit for the insulin discovery. The stakes were enormous, because before that discovery, there was no tomorrow for these patients. There was only the diet, the wasting, and the waiting.

## Summer 1921: Banting, Best, and the Lab on a Shoestring

Frederick Banting came home from the First World War with a wound and a plan, but neither paid the rent. He had tried to build a medical practice in London, Ontario, and watched it stall. By the early 1920s he was lecturing part-time at the University of Western Ontario and scraping by, which is exactly the kind of man who walks into a senior professor's office with a half-formed idea and nothing to lose.

That professor was John Macleod, head of physiology at the University of Toronto. The first meeting went badly. Macleod listened, and what he saw was a surgeon with no research background proposing to untangle one of the oldest puzzles in medicine. He was cautious, and he said so. But he did not say no. He gave Banting a bench, a modest budget and a summer, and he paired him with Charles Best, a young graduate student who could handle the chemistry that Banting could not.

Then Macleod left for Europe. For most of that summer of 1921 the Toronto lab belonged to two men and a heat wave. Banting and Best worked flat out, tying off pancreatic ducts in dogs, waiting for the enzyme-producing tissue to wither, then grinding what was left into extracts and injecting those extracts into animals made diabetic by removal of the pancreas. The room smelled of ether and dog. They ran the experiments over and over, and they wrote to Macleod in Europe with the results, thrilled with what they were seeing.

Macleod's replies must have stung. He called the experiments inconsistent. He said they lacked proper controls, that the numbers could not yet carry the weight Banting wanted to put on them. It was, in fairness, a reasonable objection from a physiologist, and it landed on a man who had already decided he was being doubted.

Here the record gets murky. As the story is usually told, Macleod returned to Toronto at the end of the summer and turned down Banting's requests for more resources, more animals, more money, more time. Some accounts say exactly that, but the detail is not reliably confirmed, so treat it as part of the legend the two men built around themselves.

What is documented is what happened in December 1921. At the meeting of the American Physiological Society, Banting stood up to present the work and faltered. He was not a confident speaker, and the room was not friendly. Macleod stepped in and finished the presentation for him. Whatever credit the audience carried out of that hall, a good share of it attached to the professor rather than the man who had spent the summer in the lab. The partnership that would produce the insulin discovery had already begun to crack, and the summer of 1921 was where the fissure opened.

## Leonard Thompson and the Injection That Changed Everything

On January 11, 1922, a 14-year-old boy named Leonard Thompson lay gravely ill in a Toronto hospital, and he became the first person to receive an injection of pancreatic extract. That first attempt did little good. His condition barely moved, and the injection brought side effects that made the whole effort look like a dead end.

Twelve days later, everything flipped. On January 23, 1922, Thompson received a second injection, and this one worked. His condition improved fast, and his blood sugar dropped markedly. For a disease that had been a death sentence, that single morning was the turning point for the insulin discovery.

Here is the part that gets skipped in most retellings. The extract that actually saved Thompson was not prepared by Frederick Banting or Charles Best. It came from James Collip, a biochemist, who used an alcohol purification method to strip the impurities out of the pancreatic extract. Banting and Best had done the summer of 1921 lab work in Toronto, but it was Collip's chemistry that turned a rough slurry into something a human body could tolerate.

And Collip learned quickly that purity cuts both ways. When he gave the extract to healthy animals, they slipped into severe hypoglycemia and died. The same substance that pulled a dying boy back could kill a healthy one if the dose was wrong. Insulin, it turned out, was not a miracle you could pour freely. It demanded careful dose control, and that lesson shaped every injection that followed.

Two injections, twelve days apart. The first showed the idea was possible. The second showed it was real. Between them sat one biochemist and a bottle of alcohol.

Some accounts say John Macleod formally announced the discovery to the scientific world in March 1922, and that Banting stayed away, reportedly because he could not cover the travel costs. That version circulates widely, but it is not reliably confirmed, so treat it as the popular telling rather than settled record. What is certain is that the credit question was already turning toxic, and the man who made the second injection work would spend years watching his contribution fade into the background.

## Georg Zülzer: The German Doctor Who Got There First

Long before the Toronto team became a household name, a German physician named Georg Zülzer had already watched a pancreatic extract pull diabetic patients back from the edge. In 1908, Zülzer showed that these extracts could lower sugar and ketone levels in people with diabetes, and could even bring some patients out of a diabetic coma. He was roughly two decades ahead of the insulin discovery that would make Banting famous.

Zülzer was confident enough in his work to give it a name and protect it. He called his preparation "Acomatol" and took out a patent on it. That patent turned out to be oddly prescient, because it described exactly the fix his early batches needed: using alcohol to strip out the impurities that were causing trouble.

And there was plenty of trouble. His extract triggered fever, chills, and vomiting in the patients who received it, the unmistakable signature of a dirty preparation. The alcohol method in his patent was his answer to that problem.

By 1914, Zülzer had backing from the pharmaceutical giant Hoffmann-La Roche, and the results looked genuinely promising. His newer extracts no longer caused fever, chills, or vomiting. Then a different problem surfaced: the experimental animals began having convulsions and slipping into coma.

He never got the chance to work out why. World War I broke out in the summer of 1914 and his research stopped almost overnight. It never regained its momentum.

What makes the story sting is what Zülzer eventually understood. The convulsions and coma were not caused by leftover impurities at all. They came from hypoglycemic shock, the result of an extract that was too pure and too potent. He had a powerful treatment sitting in his hands and could not read what it was telling him.

Roughly ten years later, the news arrived that the Nobel Prize had gone to Banting and Macleod. Zülzer was reportedly bitter about it, though the depth of his reaction is hard to confirm with certainty.

War and timing did the rest. The same finish line Banting crossed in Toronto had already been in sight in a German laboratory, and history simply looked the other way.

## Who Really Discovered Insulin?

The 1923 Nobel Prize in Physiology or Medicine went jointly to Frederick Banting and John Macleod, the University of Toronto professor of physiology who had given Banting his lab space. That shared award is the whole quarrel in miniature. Banting thought Macleod deserved nothing, and he said so, loudly, for years.

The dispute never really closed. Banting spent the rest of his life shrinking Macleod's part in the insulin discovery to almost nothing. Charles Best, the young assistant who had worked beside him through the summer of 1921, built a different sort of story over time, one that nudged his own role closer to the center of the frame. James Collip, the biochemist whose alcohol purification made the January 1922 injection work, stayed mostly in the shadows. Three men, three versions, and the record never fully settled on one.

Step back further and the picture frays even more. In 1908, the German doctor Georg Zülzer had already shown that pancreatic extracts could pull sugar and ketones down in diabetic patients, and could even bring some of them out of diabetic coma. He named his preparation Acomatol and patented it. His extracts caused fever, chills and vomiting from impurities, and his patent described using alcohol to strip those impurities out. By 1914 he had backing from Hoffmann-La Roche, and the fever and chills were gone, only for convulsions and coma to appear in his experimental animals. Then World War I began in the summer of 1914 and his research stopped cold, never regaining its momentum. Only later did he understand that the convulsions and coma came from hypoglycemic shock, the product of an extract that was too pure, not too dirty. He had held a working treatment and misread it.

So what actually made insulin succeed? Not the first spark alone. Collip's purification, the safety testing that followed, and the slow, stubborn work of convincing the scientific community all had to fall into place. The breakthrough was the easy part to celebrate. Turning it into something a doctor could hand to a dying child took a roomful of people, and only some of them got their names on the prize.

Insulin still saves millions of lives today. It only does that when it is used carefully and consciously, which is the quieter lesson running under all the noise.


## Frequently asked questions

**Who actually discovered insulin first?**

Frederick Banting and Charles Best carried out the decisive dog experiments in Toronto in the summer of 1921, and James Collip's alcohol purification turned their extract into something usable. Years earlier, in 1908, German doctor Georg Zülzer had already shown that pancreatic extracts could lower sugar and ketone levels in diabetic patients.

**Why was Frederick Banting angry about winning the Nobel Prize in 1923?**

The 1923 Nobel Prize in Physiology or Medicine was awarded jointly to Banting and John Macleod. Banting believed Macleod had no real claim to the discovery and considered sharing the honor with him an insult rather than a recognition. That resentment shaped how he spoke about the award for the rest of his life.

**What did John Macleod contribute to the discovery of insulin?**

John Macleod was Professor of Physiology at the University of Toronto, and he provided the laboratory facilities where Banting conducted his research. He also arranged for Charles Best to work alongside Banting. His role was institutional rather than hands-on, which is exactly why the Nobel decision stirred so much bitterness.

**Who was Georg Zülzer and what did he discover about pancreatic extracts?**

Georg Zülzer was a German doctor who in 1908 demonstrated that pancreatic extracts could lower sugar and ketone levels in diabetic patients and even revive some of them from diabetic coma. He named his preparation "Acomatol" and patented it, convinced of its value.

**What happened to Leonard Thompson after his first insulin injection?**

Leonard Thompson, a 14-year-old patient in serious condition, received the first injection of pancreatic extract on January 11, 1922. It had limited effect and caused side effects. A second, purified injection on January 23, 1922 worked, and his condition improved rapidly as his blood sugar dropped markedly.

**How did James Collip make insulin safe enough for human use?**

James Collip, a biochemist, used an alcohol purification method to produce a purer extract, and that is the preparation behind Thompson's successful second injection. When Collip tested the extract on healthy animals, they went into severe hypoglycemia and died, revealing that insulin required careful dose control to be safe.

**Why did World War I stop Georg Zülzer's insulin research?**

By 1914 Zülzer had backing from Hoffmann-La Roche, and his newer extracts no longer caused fever, chills or vomiting, but they triggered convulsions and coma in experimental animals. When World War I began in the summer of 1914, his work halted abruptly and never regained its momentum.

**Was Charles Best unfairly left out of the Nobel Prize?**

Best was not named in the 1923 award, which went only to Banting and Macleod. Over time Best built a narrative that placed his own role closer to the center of the insulin discovery, while Collip's contribution stayed largely in the shadows. Zülzer's earlier work remained overlooked as well. Editorial note: Details that remain unconfirmed, including the exact division of prize money and private conversations between the researchers, are presented here as they have been reported, with appropriate hedging.

Canonical: https://curio.madeda.com/insulin-discovery-the-1923-nobel-prize-rivalry/