The 1920s are often remembered as a decade of scientific progress, changing culture, and major medical discoveries. Radios became more common in homes, movies became more popular, and doctors made important advances in medicine. One of the greatest medical breakthroughs of the decade was the discovery and development of insulin.
Before insulin existed, diabetes was one of the deadliest diseases in the world. Many children diagnosed with type 1 diabetes died only months or years after learning they had the disease. Doctors understood that diabetes affected blood sugar levels, but they had no reliable way to treat it. Instead, patients were placed on extremely strict diets that often left them weak and starving.
The article History of Insulin explains, “Before the availability of insulin, the life expectancy of children with diabetes mellitus was short and the prognosis for the adult onset diabetes was very poor.” Because doctors had no effective treatment, “physicians Allen and Joslin endorsed fasting and calorie restricted diets for diabetes.” These starvation diets sometimes delayed death, but they could not cure the disease. Patients often became dangerously thin because they were forced to eat very little food in order to survive longer.
Scientists knew that the pancreas played an important role in diabetes, but they struggled to isolate the substance responsible for controlling blood sugar. According to the Diabetes UK article, “Attempts had been made to extract insulin from ground up pancreas cells, but they’d all proved unsuccessful.” The problem was that other tissues inside the pancreas destroyed the insulin before it could be used.
During the early 1920s, however, a small group of researchers in Canada changed medical history forever. Frederick Banting, Charles Best, John Macleod, and James Collip worked together to isolate insulin and develop it into a treatment that could save human lives. Their discovery quickly became one of the most important medical breakthroughs of the twentieth century.
Diabetes Before Insulin
Before insulin was discovered, diabetes was extremely difficult to treat. Patients with severe diabetes often experienced constant thirst, rapid weight loss, weakness, and exhaustion. Children diagnosed with type 1 diabetes almost always died because their bodies could no longer produce insulin naturally.
Doctors understood some parts of the disease, but they did not know how to stop it. Most treatments focused only on reducing symptoms instead of curing the condition. Starvation diets became one of the main methods used by doctors because reducing food intake sometimes lowered blood sugar levels temporarily.
The History of Insulin article explains that these treatments “resulted in some improvement of glucosuria and acidosis, decreased coma, and delayed death among children with diabetes.” Even so, patients still suffered greatly, and most eventually died from the disease.
Scientists continued studying the pancreas because they believed it released a substance that controlled blood sugar. The article explains, “Long before the discovery of insulin, it was hypothesized that the pancreas secreted a substance that controlled carbohydrate metabolism.” Researchers spent years attempting to isolate this substance, but impurities and toxic materials inside pancreatic extracts caused experiments to fail repeatedly.
Frederick Banting and the Beginning of Research
The breakthrough finally began in 1920 when Frederick Banting developed a new theory about how insulin could be isolated safely. Banting was a Canadian surgeon rather than an experienced scientist, but he became interested in diabetes research after reading medical articles about the pancreas.
The Diabetes UK article explains that Banting read research suggesting “insulin producing cells in the pancreas are slower to deteriorate than other pancreas tissue.” Banting realized that this discovery might allow scientists to destroy harmful pancreatic tissue while preserving the cells that produced insulin.
The article explains, “Banting realised that this might allow for the removal of insulin by breaking down the pancreas in a way that would leave just the cells that produce insulin intact.”
Although Banting believed strongly in his idea, he knew he needed scientific support to test it. On November 7, 1920, he met with John Macleod, a professor at the University of Toronto who specialized in diabetes research. Macleod agreed to provide laboratory space, experimental dogs, and a student assistant named Charles Best.
The History of Insulin article explains that Macleod “granted him laboratory space, ten dogs for his experiments, a student research assistant (Charles Best), and provided supervision and guidance.”
This partnership became the beginning of one of the most important scientific discoveries in modern medicine.
Early Experiments and Insulin
The insulin experiments officially began in May 1921. According to the Diabetes UK article, “On 17 May 1921 Banting, Best and Macleod first got together to begin their research.”
The researchers worked mainly with dogs. They tied off pancreatic ducts to destroy parts of the pancreas while keeping the insulin producing cells alive. Afterward, they created pancreatic extracts and tested them on diabetic dogs whose pancreases had been removed.
The History of Insulin article explains that “the experiments began on May 17, 1921.” By September, the experiments began showing successful results. The article explains that “intravenous injection with their pancreatic extract, which they named isletin, lowered the blood glucose.”
These results were extremely important because they proved that pancreatic extracts could lower blood sugar levels in diabetic animals. For the first time, researchers had strong evidence that insulin could become a treatment for diabetes.
The experiments were difficult and time consuming. Many failed completely, but Banting and Best continued working every day in the laboratory. According to the Diabetes UK article, “Progress was initially slow.” Still, the researchers noticed regular improvements in blood sugar levels during successful experiments.
The article explains that “By November, they’d successfully treated a dog with diabetes with their insulin extract for 70 days.” This achievement demonstrated that insulin could keep diabetic animals alive much longer than before.
James Collip and Purifying Insulin
Although the experiments on dogs were successful, another major problem still existed. The insulin extract was not pure enough for use in humans. Impurities inside the extract caused dangerous side effects and made the treatment unreliable.
To solve this problem, biochemist James Collip joined the research team in December 1921. The Diabetes UK article explains, “James Collip, a biochemist, joined the group to work on purifying insulin so it would be safe enough to be tested in humans.”
Collip worked constantly to improve the insulin extract. His goal was to remove impurities while keeping the insulin effective. According to the article, “With his help, a more concentrated and pure form of insulin was developed.”
This purification process became one of the most important parts of the entire discovery because insulin could not be safely tested on humans without it.
Leonard Thompson and the First Human Injection
In January 1922, the researchers attempted one of the most important medical experiments in history. A fourteen year old boy named Leonard Thompson became the first human patient to receive insulin treatment.
The Diabetes UK article explains, “In January 1922, Leonard Thompson, a 14 year old boy dying from type 1 diabetes, became the first person to receive an injection of insulin.”
Leonard was extremely sick and close to death because of diabetes. Doctors hoped the insulin extract might save his life.
The first injection showed both promise and problems. According to the History of Insulin article, “The first injection of the pancreatic extract to a 14 year old boy by Banting and Best on January 11, 1922, caused a sterile abscess.” The injection lowered blood sugar somewhat, but the extract still contained impurities that caused complications.
Collip immediately continued purifying the insulin. He worked day and night to improve the extract before another injection was attempted.
Later in January, Leonard received a second injection. This time the results were historic. The Diabetes UK article explains, “This time it was a complete success and Leonard’s blood sugar levels become near normal, with no obvious side effects.”
The article then states, “For the first time in history, type 1 diabetes was not a death sentence.”
The successful treatment of Leonard Thompson changed medicine forever. Doctors now had a treatment capable of saving patients who otherwise would have died.
The International Announcement of Insulin
After the successful human treatments, news about insulin spread quickly throughout the medical world. Researchers and doctors recognized immediately that the discovery could transform diabetes treatment permanently.
The Diabetes UK article explains, “On 3 May 1922, Macleod announced the discovery of insulin to the international medical community.” Macleod presented the research at a meeting of the Association of American Physicians in Washington.
The article also explains that this was “the first time the team used the word ‘insulin’.”
Doctors and scientists responded with excitement because the treatment offered hope to diabetic patients around the world.
Insulin Belongs to the World
As insulin became more successful, questions arose about patents and ownership. Banting and the other researchers believed insulin should remain available to everyone who needed it instead of becoming a private source of profit.
The Diabetes UK article explains, “On 23 January 1923, Banting, Collip and Best were awarded U.S. patents on insulin and the method used to make it.” However, instead of keeping the patents for themselves, the researchers sold them to the University of Toronto for only one dollar each.
The article explains, “Banting famously said, ‘Insulin does not belong to me, it belongs to the world.’”
This decision helped insulin become widely available much more quickly.
Mass Production and Worldwide Expansion
As reports of insulin’s success spread, demand increased rapidly. Pharmaceutical companies began working with the researchers to produce insulin on a much larger scale.
According to the Diabetes UK article, “Eli Lilly become the first manufacturer to mass produce insulin.” In October 1923, the company began shipping commercial insulin supplies.
The History of Insulin article explains that early insulin production still faced challenges. “Eli Lilly began producing insulin from animal pancreas but fell short of the demand, and the potency varied up to 25% per lot.”
Scientists continued improving insulin production methods to make the medicine more reliable and more widely available. The article explains, “The development of an isoelectric precipitation method led to a purer and more potent animal insulin.”
Insulin also spread internationally during 1923. The History of Insulin article explains, “In 1923, August Krogh, from the University of Copenhagen, met with Banting and Macleod to learn more about insulin because his wife had diabetes mellitus.”
Krogh later helped establish insulin production in Scandinavia, allowing the treatment to reach even more patients.
The Nobel Prize
The discovery of insulin quickly became recognized as one of the greatest medical achievements in history. In 1923, Frederick Banting and John Macleod received the Nobel Prize in Physiology or Medicine.
The Diabetes UK article explains, “In recognition of their life saving discovery, Banting and Macleod were jointly awarded the 1923 Nobel Prize in Physiology or Medicine.”
The Nobel Prize helped make the insulin researchers internationally famous. Banting shared part of his prize money with Charles Best, while Macleod shared his portion with James Collip. This reflected the teamwork involved in the discovery.
The Significance of Insulin
The discovery and development of insulin during the 1920s completely transformed medicine. Before insulin, severe diabetes almost always led to death. After insulin became available, millions of people gained the chance to survive and live much longer lives.
The History of Insulin article explains, “The discovery of insulin in 1922 marked a major breakthrough in medicine and therapy in patients with diabetes.”
The development of insulin also demonstrated the importance of scientific cooperation. Banting, Best, Macleod, and Collip all contributed different skills to the project. Without their combined efforts, insulin might not have been discovered when it was.
The success of insulin encouraged future medical research as well. Scientists realized that diseases once considered hopeless could potentially be treated through careful experimentation and teamwork.
Today, historians continue studying the discovery of insulin because it remains one of the most important medical breakthroughs in modern history. Millions of people around the world still rely on insulin every day, and the events of the 1920s permanently changed diabetes treatment forever.
Timeline of Events
1918 – Doctors mainly use starvation diets to treat diabetes.
7 November 1920 – Frederick Banting meets John Macleod to discuss insulin research.
17 May 1921 – Banting, Best, and Macleod officially begin insulin experiments.
September 1921 – Researchers discover insulin extracts lower blood sugar in dogs.
10 November 1921 – Scientists successfully treat a diabetic dog for 70 days.
12 December 1921 – James Collip joins the research team to purify insulin.
11 January 1922 – Leonard Thompson receives the first insulin injection.
23 January 1922 – Purified insulin successfully treats Leonard Thompson.
3 May 1922 – Insulin is officially announced to the medical community.
23 January 1923 – Banting, Best, and Collip sell insulin patents to the University of Toronto for $1 each.
15 October 1923 – Eli Lilly begins mass production of insulin.
25 October 1923 – Banting and Macleod receive the Nobel Prize.
Works Cited
DIABETES UK. 2024. “100 Years of Insulin.” Diabetes UK. 2024. https://www.diabetes.org.uk/our-research/about-our-research/our-impact/discovery-of-insulin.
Quianzon, Celeste C, and Issam Cheikh. “History of insulin.” Journal of community hospital internal medicine perspectives vol. 2,2 10.3402/jchimp.v2i2.18701. 16 Jul. 2012, doi:10.3402/jchimp.v2i2.18701
