A purified insulin treatment given to 14-year-old Leonard Thompson in Toronto in January 1922 marked the breakthrough that transformed Type 1 diabetes from a fatal disease into a manageable condition.
Insulin’s discovery in the early 1920s transformed diabetes from a near-certain death sentence into a manageable chronic condition, and the breakthrough reached a decisive moment in Toronto in January 1922. According to the U.S. Food and Drug Administration and the National Institute of Diabetes and Digestive and Kidney Diseases, Frederick Banting, John Macleod and Charles Best began experiments in 1921 to isolate the hormone from the pancreas, laying the groundwork for the first effective treatment for people with Type 1 diabetes.
The early work was promising but far from ready for patients. Banting and Best’s extracts still needed significant purification before they could be safely used in people, and that challenge brought biochemist James Collip into the team. By refining the preparation, he helped make insulin suitable for human use, a step that proved decisive for the first successful treatment.
That breakthrough came with Leonard Thompson, a 14-year-old who was gravely weakened by diabetes. The first injection, given on 11 January 1922, did not produce the desired result. After further purification, a second injection on 23 January brought a clear improvement, with blood glucose and urinary sugar and ketone levels falling. Thompson lived for another 13 years after treatment began, dying in 1935 at the age of 27, according to historical accounts cited by the FDA and other medical sources.
The medical significance of the discovery was quickly recognised. Banting and Macleod received the Nobel Prize in Physiology or Medicine in 1923, while early insulin production relied largely on extracts from cattle and pig pancreases before later advances made human insulin possible. Yet, as modern reviews from Nature, Frontiers in Endocrinology and the NCBI note, the history of insulin is also a reminder that access remains uneven in parts of the world, even a century after the drug first changed the course of diabetes care.
Disclaimer: This content is for informational purposes only and is not intended to be a substitute for professional medical judgment, advice, diagnosis, or treatment.
