A 14-year-old boy lay dying at 65 pounds, drifting in and out of consciousness. His father agreed to inject him with an experimental drug never tested on humans. That injection changed medicine forever.
Toronto General Hospital, early January 1922. Leonard Thompson was disappearing. At 14 years old, he weighed only 65 pounds. His hair was falling out. The smell of acetone hung on his breath—a sign his body was consuming itself. He drifted in and out of a diabetic coma.
Three years earlier, Leonard had been diagnosed with Type 1 diabetes. In 1919, that diagnosis was a death sentence. There was no treatment. No cure. Just a brutal countdown to the inevitable.
The only thing doctors could offer was starvation. They called it “careful dietary regulation.” Leonard’s doctor restricted him to 450 calories a day—less than two small meals. The logic was cruel but simple: if sugar was killing him, he should eat almost nothing that could become sugar.
It bought him time. Not much. Not enough.
Children with diabetes wasted away on these starvation diets. Some lasted a year. Most didn’t make it that long. They died of malnutrition if the disease didn’t kill them first. Parents watched their children fade, knowing there was nothing anyone could do.
By December 1921, Leonard was out of time. His parents, Harry and Florence Thompson, brought him to Toronto General Hospital. He was skeletal. Weak. Slipping away.
The doctors told Harry Thompson the truth: his son was dying. There was nothing conventional medicine could offer.
But there was something unconventional. Something experimental. Something that had never been tried on a human being.
Harry Thompson had to make an impossible choice.
While Leonard fought for his life, a young surgeon named Frederick Banting was working on a theory in a makeshift laboratory at the University of Toronto. Banting believed the pancreas produced an internal secretion that regulated blood sugar. If he could isolate it, maybe—just maybe—he could treat diabetes.
Banting was tenacious but not particularly distinguished. When he’d first approached Professor John Macleod with his idea, Macleod had been skeptical. Eventually, Macleod gave Banting a cramped lab, some dogs to experiment on, and a medical student named Charles Best to help with the chemistry.
Through the summer of 1921, Banting and Best worked obsessively. They removed the pancreases from dogs, induced diabetes, then injected the animals with pancreatic extract. The results were undeniable: blood sugar dropped. Symptoms improved. Dogs on the verge of death recovered.
Colleagues looked at their “thick brown muck” and doubted it would ever work in humans.
By November 1921, Banting and Best had announced their discovery to the scientific community. By January 1922, with biochemist James Collip working to purify the extract and Macleod providing oversight, they had something they believed might work in a human patient.
They needed someone desperate enough to try.
Leonard Thompson was that desperate.
On January 11, 1922, doctors administered the first human injection of pancreatic extract. Leonard’s father stood by, watching, praying, hoping for a miracle.
The injection failed.
The extract was too impure. Leonard developed hives—an allergic reaction. His blood sugar barely moved. There was no improvement. No miracle. Just a sick boy getting sicker.
The team could have given up. The first human trial had failed. They could have concluded it was too dangerous, too unpredictable, impossible to translate from dogs to humans.
Instead, they went back to the lab.
James Collip worked day and night to refine the purification process. He optimized the alcohol extraction, removed protein contaminants, washed away lipids and salts. He created a purer, more concentrated formula.
Twelve days passed. Twelve days of Leonard growing weaker. Twelve days of his parents watching and waiting.
On January 23, 1922, doctors injected Leonard Thompson with the refined extract for the second time.
This time, something happened.
Within hours, Leonard’s blood sugar levels plummeted from dangerously high to near normal. The acetone smell on his breath began to fade. His vital signs stabilized.
His medical records documented what happened next: “The boy became brighter, more active, looked better and said he felt stronger.”
Leonard Thompson—the skeletal 14-year-old who’d been hours from death—started to recover.
He received daily injections from January 23 through early February. He gained weight. His strength returned. The color came back to his face. In May 1922, he went home.
The news spread like wildfire. A dying boy had been brought back from the edge. A disease that had been an absolute death sentence for thousands of years suddenly had a treatment.
Newspapers around the world ran the story. The New York Times declared: “One by one the implacable enemies of man, the diseases which seek his destruction, are overcome by science. Diabetes, one of the most dreaded, is the latest to succumb.”
But there was a problem: supply.
Parents flooded the University of Toronto with desperate letters. My daughter is dying. My son has weeks to live. Please, can you send insulin? The demand was overwhelming. The team could barely produce enough for Leonard and a handful of other critically ill patients in Toronto.
Between March and May 1922, production actually failed completely. Collip couldn’t replicate his purification process reliably at scale. Leonard went months without steady insulin supply, surviving on whatever batches the team could produce.
It wasn’t until October 1922 that Leonard finally had a permanent, steady supply of insulin.
That’s when Eli Lilly Company entered the picture. Initially reluctant, the pharmaceutical company partnered with the University of Toronto in mid-1922. They developed industrial-scale production method. By 1923, they were shipping insulin across North America and around the world.
Children who would have died started living. Parents who’d been preparing funerals started planning futures.
In October 1923—just 21 month after Leonard’s first successful injection—the Nobel Committee awarded the Prize in Physiology or Medicine to Frederick Banting and John Macleod.
It remains the shortest time between a medical discovery and a Nobel Prize in history.
Banting was furious that Charles Best hadn’t been included. He immediately announced he was sharing his prize money with Best. Macleod followed suit, sharing his portion with James Collip.
All four men knew the truth: this hadn’t been one person’s genius. It had been collaboration, persistence, and one desperate father’s willingness to let his dying son become a guinea pig for an untested treatment.
Leonard Thompson lived for 13 more years on insulin. He gained weight. He grew. He lived a relatively normal teenage life and young adulthood—something that would have been impossible three years earlier.
On April 20, 1935, Leonard Thompson died of pneumonia at age 27. The pneumonia was likely a complication of his diabetes, but it wasn’t diabetes that killed him. Insulin had given him 13 years. Thirteen years to grow up. Thirteen years his parents never thought they’d have.
Without insulin, Leonard would have died in January 1922 at age 14. Because of insulin, he lived to 27.
Today, more than 100 years later, millions of people live full lives with Type 1 diabetes. They use insulin pens, insulin pumps, continuous glucose monitor. They go to school, build careers, have families, grow old.
Every single one of them owes their life to a 14-year-old boy named Leonard Thompson and his father’s courage to try something no one had ever tried before.
Because sometimes progress doesn’t come from certainty. It comes from desperate hope. From parents willing to risk everything for a chance. From scientists willing to keep trying after failure. From one person agreeing to be first when “first” might mean death.
Leonard Thompson was the bridge between a world where diabetes was always fatal and a world where it’s simply something you manage.
His legacy isn’t in textbooks or monuments. It’s in every person alive today because of insulin. It’s in every parent who didn’t have to bury a child with diabetes. It’s in every life that continued instead of ending.
The next time you see someone check their blood sugar or use an insulin pen, remember: that simple act was impossible until a 14-years-old boy and his desperate father said yes to an untested injection.
Leonard Thompson proved something essential: hope is never a lost cause. Even when doctors have no answer, even when death seems certain, even when you’re down to your last option—sometimes that last option is the one that changes everything.
He was the first person to receive insulin. He was the first to prove it could works. He was the first to show the world that diabetes didn’t have to be a death sentence.
And because he went first, millions of others got to go second, third, fourth—got to live when they should have died.
That’s not just a medical breakthrough. That’s a revolution. One injection, one boy, one impossible choice that change medicine forever.
In honor of Leonard Thompson (1908-1935), the first person to receive insulin and live—proving that sometimes the most powerful medicine isn’t certainty, it’s courage.