This year’s World Diabetes Day on 14th November coincides with the centenary anniversary of this ground-breaking discovery. We take a closer look at the research breakthrough that has improved, and in many cases saved, the lives for people living with diabetes ever since.

2021 marks the 100th year anniversary of the discovery of insulin – a landmark moment for people living with diabetes worldwide.

The discovery is still considered to be one of the most significant medical developments in history, which transformed diabetes from a fatal disease to a manageable condition and prolonged life for decades.

A century later, insulin remains the only available treatment for type 1 diabetes.

This November is the centenary of the first successful test of insulin at the University of Toronto in Canada. The result marked the beginning of a wave of successful trials on people living with diabetes, all achieved by a group of researchers dedicated to treating the condition.

Within months, mass-production of the life-saving drug began across North America and was soon made available elsewhere as it was shipped to the rest of the world.

Banting and Best


Prior to the discovery of insulin, life was incredibly difficult for people living with diabetes.

The condition was first recorded as far back as 1550BC in ancient Egypt, when physicians identified and noted the symptoms of an unknown illness that caused thirst, excessive urination and eventually death.

Before the introduction of insulin therapy, medical science failed to develop any effective treatment for the condition and a diagnosis of diabetes was fatal.

Patients were expected to live only one or two years before entering diabetic ketoacidosis (DKA) and succumbing to the condition.

Over time efforts were made by physicians to control the effects of diabetes.

The understanding that carbohydrate and sugar intake was connected to the condition sparked a wave of dietary programs intent on negating the effects of diabetes.

Apollinaire Bouchardat, a French pharmacist and diabetologist, introduced popular sugar-free diets which often reduced the sugar discovered in patients’ urine.

Meanwhile, other physicians such as Pierre Adolphe Piorry, believed that consuming excess calories would contradict the loss of calories in urine.

Such diets were commonly experimented with, most of which resulted in the rapid decay of their patient’s health.

As late as 1915, new approaches with diets were being adopted by scientists’ intent on providing an effective treatment for diabetes.

Two of the most prominent diabetes specialists in America, Frederick M. Allen and Elliott P. Joslin, introduced a severe restricted diet to prolong the life of those living with diabetes.

Commonly referred to as “starvation diets,” Allen and Joslin prescribed a daily intake of just 500 calories along with periods of intense fasting.

Only in the final decades of the 19th century did a loose understanding of the science behind diabetes begin to emerge.

 In 1889, two German scientists correctly identified a link between the pancreas and diabetes.

Three decades before this, one of the most significant discoveries of this period occurred in Germany, when scientist Paul Langerhans correctly identified in a study that the pancreas served two primary functions and secrete some sort of hormone.

Langerhans study of the pancreas led to the discovery of the islets of Langerhans, a group of insulin-producing cells in the pancreas, also known as islet cells.

This discovery would prove crucial in the later scientific breakthrough at the University of Toronto.

Banting And Best And A Dog


In November 1920, Canadian surgeon Frederick Banting began exploring how insulin could be extracted from islet cells in the pancreas.

He started working at the University of Toronto, with support from Professor J. J. R. Macleod, a physiology professor and global expert in diabetes.

 Macleod provided Banting with a laboratory and assigned Charles Best, a promising research student, to assist Banting with his experiments.

In May 1921, Banting and Best began removing the pancreas from research dogs and performed pancreatic duct ligation to separate insulin-producing cells from the rest of the pancreas.

By November, they successfully extracted insulin from the pancreas and successfully treated a dog with diabetes for 70 days.

The promising results allowed for human trials to be considered for the first time. Biochemistry professor James Collip was introduced to purify the insulin, allowing it to be safely administered to people living with diabetes.

First person to be treated with insulin

On 11 January 1922, Leonard Thompson became the first person to be treated with insulin.

Leonard was aged 14 and had been living with diabetes for two and half years before being admitted to Toronto General Hospital. Like many diabetes patients, he was severely ill and weighted just 65 pounds.

Leonard had been placed on a “starvation diet” by his doctors, which restricted him to just 450 calories a day.

The first dose of insulin administered to Leonard lowered his blood glucose levels by around a quarter and reduced the level of glucose in his urine.

 However, due to impurities present in the insulin, an abscess developed around the injection site and Leonard’s ketone levels remained dangerously high.

Collip continued his work on purifying the insulin and achieved success shortly thereafter.

On 23rd January, Leonard received his second dose of insulin.

Within 24 hours, his blood glucose levels dropped by around 77% and his physical appearance improved remarkedly.

Just three months later, he “looked better” and “felt stronger” and was discharged from hospital.

Leonard was not the only success story. Five-year-old Teddy Ryder was among the first group of patients treated by Banting and Best’s insulin at Toronto General Hospital in 1922.

One of the youngest patients to be treated with insulin, Teddy weighed only 26 pounds and could hardly move before the breakthrough in Toronto.

With access to insulin, Teddy made a remarkable recovery, and lived for a further 77 years.

Leonard Thompson Image

Worldwide impact

The remarkable success of the first human trials led to rapid clinical deployment of insulin therapy across the globe.

In 1923, the American pharmaceutical company Lilly began to ship the first commercial stock of insulin across North America.

Just one month later, Nordisk Insulin Laboratory started producing insulin in Denmark and began shipping vials globally.

The incredible work of Banting, Best, Macleod and Collip marked the end of diabetes as a terminal condition. In recognition of their achievement, Banting and Macleod were awarded the Nobel Prize in Physiology or Medicine.

 They divided their prize money equally with Best and Collip, who had both been overlooked despite their significant contributions.

Finally, people with diabetes had access to a treatment which prolonged life by decades, whilst crucially enhancing their quality of life.

However, the development of insulin had only just begun, and over the coming decades insulin therapy and delivery developed significantly.

Frederick Grant Banting. Wellcome Collection. 12303I


The production and delivery of insulin continued to be developed in the decades following the breakthrough at Toronto.

The introduction of synthetic human insulin in 1982 was a significant milestone in the treatment of diabetes, as it allowed for insulin to be genetically engineered in laboratories, ending the practice of extracting insulin from cattle and pigs.

The discovery remains one of the most important medical breakthroughs in history. To the present day, millions of people still rely on insulin. It ignited a century of development in diabetes care and has undoubtedly saved millions of lives.

At DRWF, we think it is time for the next big breakthrough; our ultimate goal is to find a cure for diabetes. In pursuit of this, we fund some of the best and brightest diabetes researchers in the UK and around the world, whose work improves our understanding of diabetes; explores new treatments; develops self-management strategies; and seeks out potential cure pathways.

The dedication and commitment of our diabetes research community is second to none.

Through our awareness raising, information resources and educational support programmes, we enable people with all types of diabetes to learn more about their condition, providing the tools to motivate, empower and engage in a pro-active approach to good self-care.

Every day, we do our utmost to ensure that people living with diabetes are ‘staying well until a cure is found…’

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