Timeline Entry
On 11 January 1922, fourteen-year-old Leonard Thompson received an injection of pancreatic extract at Toronto General Hospital. It was the first use of insulin in a person with diabetes, but the first attempt was not the dramatic success that later memory sometimes suggests.
The turning point came twelve days later, when a more purified extract was given on 23 January. Thompson's improvement made insulin therapy clinically credible and moved the Toronto work from experimental physiology into the history of life-saving treatment.
Clinical Event
Thompson had been admitted to Toronto General Hospital in December 1921 with severe diabetes. Before insulin, patients in his condition were often treated with extremely restrictive diets that could delay death but rarely restored strength or long-term health.
The first dose used a pancreatic extract prepared by Banting and Best. It produced only limited clinical benefit and caused a sterile abscess at the injection site, showing that the extract was still too impure for dependable treatment.
Biochemist James Collip worked to improve the preparation. On 23 January, Thompson received the refined extract, and the response was far more convincing: sugar and ketones in the urine fell sharply, blood sugar dropped, and his condition visibly improved.
The episode was not only a laboratory achievement. It depended on a hospital patient close to death, clinicians willing to test a new therapy, and bedside observation that could translate chemical effect into medical significance.
Historical Context
Diabetes was recognized long before the twentieth century, but the connection between the pancreas and diabetes became especially important after nineteenth-century experiments showed that removal of the pancreas could produce severe diabetes in animals. By 1921, the University of Toronto group had turned that line of research toward treatment.
The broader insulin therapy story began with laboratory extracts and animal experiments, but the Thompson case gave the work its clinical force. The successful January 1922 treatment showed that a pancreatic extract could reverse key signs of diabetes in a human patient, at least when the preparation was potent and sufficiently purified.
Debates and Credit
The first patient use of insulin is often compressed into a simple breakthrough story, but the historical record is more complex. Banting and Best prepared the early extract; Macleod supplied laboratory space, supervision, and physiological expertise; Collip's purification work made the second treatment successful; and hospital clinicians, including W.R. Campbell, directed care at the bedside.
Credit disputes followed almost immediately. Banting and Macleod received the 1923 Nobel Prize in Physiology or Medicine, while Banting shared his prize money with Best and Macleod shared his with Collip. That division of recognition reflected the tension between discovery, purification, clinical testing, and production, all of which were necessary for insulin to become a usable therapy.
Legacy
Thompson lived for years after the first treatment, a fact that made the promise of insulin visible to physicians, patients, and families. Insulin did not cure diabetes, and it did not remove the need for diet, monitoring, medical supervision, or reliable supply. It did, however, change the likely course of severe diabetes in a way that few earlier therapies had achieved.
The 1922 patient trial also helped define a pattern of twentieth-century medicine: laboratory research becoming hospital therapy, then dependent on purification, standardization, and manufacture. For the wider setting, read the History of Diabetes and Insulin topic guide and the profile of Frederick Banting.
Further Reading
The classic historical account of the Toronto group, Leonard Thompson, the clinical trials, and the conflicts over recognition.
Places the insulin episode within the longer history of diabetes, diagnosis, diet therapy, patient experience, and chronic care.
Useful for understanding Collip's purification work and the research culture that made clinical insulin possible.