More than a century ago, a diagnosis of type 1 diabetes usually came with a brutally short timeline. Today, people use insulin pens, wearable glucose sensors, smartphone-connected pumps, and automated dosing systems while going to school, building careers, raising families, and occasionally eating birthday cake without first drafting a laboratory protocol.
Insulin did not cure diabetes. What it did was almost as revolutionary: it transformed the disease from an often rapidly fatal condition into one that could be managed over a lifetime. During the decades that followed, insulin therapy also became safer, purer, faster, longer-lasting, easier to deliver, and increasingly personalized.
The history of insulin is therefore more than a story about one medication. It is the story of how diabetes care evolved from starvation diets and uncertain survival to continuous glucose monitoring, insulin pumps, and systems that can automatically adjust doses day and night.
Diabetes Care Before Insulin: Survival by Starvation
Insulin is a hormone made by beta cells in the pancreas. It helps glucose move from the bloodstream into cells, where it can be used for energy. In type 1 diabetes, the immune system destroys most of these insulin-producing cells. In type 2 diabetes, the body may resist insulin’s effects and eventually fail to produce enough to meet its needs.
Before insulin therapy, doctors had very little to offer people with severe diabetes. The most widely used approach was an extremely restrictive diet containing minimal carbohydrates and calories. These so-called starvation diets could sometimes reduce glucose levels and extend life for a short period, but they could not replace the missing hormone.
Children with type 1 diabetes often became dangerously thin. Their bodies could not use glucose normally, so they broke down fat and muscle for fuel. Many developed diabetic ketoacidosis, or DKA, a life-threatening condition caused by a severe lack of insulin. Families watched children weaken despite following punishing diets with military precision. Dinner was not merely disappointing; it was part of a desperate attempt to buy time.
Diabetes specialists could slow the decline, but they could not stop it. That changed dramatically in the early 1920s.
The Discovery That Changed the Prognosis of Diabetes
The Toronto research team
In 1921, surgeon Frederick Banting and medical student Charles Best began experiments at the University of Toronto under the supervision of physiologist John Macleod. Their goal was to isolate the substance produced by the pancreas that controlled blood sugar. Biochemist James Collip later helped purify the pancreatic extract so that it could be administered more safely to people.
The work was not a neat movie montage involving three test tubes and an inspirational violin. The researchers faced failed experiments, inconsistent extracts, disagreements, limited equipment, and the difficult task of separating insulin from other pancreatic substances.
Leonard Thompson and the first successful treatment
In January 1922, Leonard Thompson, a critically ill teenager with diabetes at Toronto General Hospital, became the first person to receive the experimental pancreatic extract. The initial preparation produced disappointing results and caused an adverse reaction. Collip then improved the purification process.
A second treatment produced a dramatic reduction in Thompson’s blood glucose and ketones without the same severe reaction. The medical world suddenly had evidence that replacing insulin could reverse the immediate metabolic crisis of type 1 diabetes.
What had been a near-certain death sentence was becoming a treatable condition. Insulin production expanded rapidly, with pharmaceutical manufacturers developing methods to purify animal-derived insulin on a commercial scale. By 1923, insulin was reaching patients well beyond Toronto.
From Animal Extracts to Biosynthetic Human Insulin
Early animal-derived insulin
For decades, insulin was extracted mainly from the pancreases of pigs and cattle collected by the meat-processing industry. Porcine and bovine insulin are structurally similar enough to human insulin to lower blood glucose effectively. These products saved countless lives, but early formulations could contain impurities and sometimes caused allergic or immune reactions.
Producing insulin also required enormous quantities of animal tissue. Historical accounts describe tons of pancreatic material being processed to make relatively small amounts of purified insulin. It was lifesaving medicine made through an industrial procedure that was neither elegant nor especially convenient.
Manufacturing and purification improved over time. Researchers also learned how to modify insulin’s absorption. Adding substances such as protamine or zinc could slow its action, allowing patients to take fewer injections and achieve more stable coverage between meals and overnight.
The biotechnology revolution
A major turning point arrived in 1982, when the U.S. Food and Drug Administration approved Humulin, the first biosynthetic human insulin and the first approved medical product manufactured using recombinant DNA technology.
Instead of extracting insulin from animal organs, scientists inserted the genetic instructions for human insulin into microorganisms that could produce it under controlled conditions. The resulting insulin matched the human hormone more closely, improved consistency, and reduced dependence on animal sources.
This achievement did more than modernize diabetes treatment. It helped launch the biotechnology industry and demonstrated that genetically engineered organisms could manufacture complex human medicines safely and at scale.
Insulin Analogs Made Treatment More Flexible
Human insulin was a tremendous advance, but it still did not perfectly imitate the pancreas. Naturally produced insulin rises quickly after food and falls as glucose is handled. Injected regular human insulin acts more slowly, which can make meal timing awkward and increase the risk of glucose rising too high immediately after eating or falling too low several hours later.
Researchers addressed this problem by adjusting the insulin molecule. These modified products, known as insulin analogs, retain insulin’s glucose-lowering function but are absorbed at different speeds.
Rapid-acting insulin
The FDA approved insulin lispro, the first rapid-acting insulin analog, in 1996. Other rapid and ultra-rapid formulations followed. These insulins begin working more quickly than regular human insulin, allowing doses to be taken closer to meals and helping control post-meal glucose spikes.
Long-acting basal insulin
Long-acting analogs were designed to provide steadier background insulin with fewer pronounced peaks. Newer basal products may work for roughly a full day or longer, depending on the formulation and the individual using it.
Combining basal insulin with rapid-acting mealtime doses created a more physiological treatment strategy. Instead of forcing daily life to follow a rigid insulin schedule, clinicians could increasingly tailor insulin therapy to eating patterns, activity, illness, sleep, and personal routines.
That does not mean modern insulin is effortless. Doses still require careful adjustment, and too much insulin can cause hypoglycemia. Nevertheless, the menu of insulin types gives patients and clinicians far more flexibility than earlier generations had.
Better Insulin Delivery Changed Everyday Life
From reusable glass syringes to insulin pens
Early insulin users often relied on reusable glass syringes and large metal needles that had to be cleaned, sterilized, and sometimes sharpened. It was diabetes care with the atmosphere of a home chemistry laboratory.
Disposable plastic syringes and finer needles eventually made injections safer and less painful. Insulin pens then simplified dose measurement by combining the medication and dosing mechanism in one portable device. Modern pens may include memory functions or digital connectivity that records when and how much insulin was taken.
These changes matter because a treatment can work only when people can realistically use it. Reducing preparation time, discomfort, and dosing confusion makes insulin therapy easier to fit into school, travel, restaurants, workplaces, and family life.
Insulin pumps
Insulin pumps deliver small amounts of rapid-acting insulin throughout the day as basal coverage. Users can also request additional bolus doses for meals or high glucose levels. Some pumps use tubing connected to an infusion set under the skin, while patch pumps attach directly to the body without external tubing.
Pumps allow basal rates to vary by time of day. A person who needs more insulin before waking, less during exercise, or a temporary reduction during illness recovery can make targeted adjustments rather than changing an entire day’s injection plan.
Pumps are not automatic perfection machines. Infusion sites can fail, devices require training, and interrupted insulin delivery can quickly become dangerous for someone with type 1 diabetes. Even so, pump therapy has given many people greater dosing precision and freedom.
Glucose Monitoring Made Insulin Safer and Smarter
Insulin’s effectiveness depends on knowing what glucose is doing. Early patients relied heavily on urine testing, which provided delayed and limited information. Home blood glucose meters later allowed people to check a small blood sample and make immediate treatment decisions.
This changed the relationship between patients and diabetes care. Instead of waiting for occasional clinic measurements, people could see how food, exercise, stress, illness, sleep, and insulin affected them throughout the day.
The lesson of intensive glucose management
The landmark Diabetes Control and Complications Trial, conducted from 1983 to 1993, showed that intensive treatment using multiple daily insulin injections or a pump, combined with frequent glucose checks, could significantly delay or reduce complications involving the eyes, kidneys, and nerves in people with type 1 diabetes.
The findings helped establish a principle that now seems obvious but required strong evidence: maintaining glucose closer to a healthy range can protect long-term health. The challenge was achieving better control without causing excessive hypoglycemia.
Continuous glucose monitoring
Continuous glucose monitors, commonly called CGMs, transformed monitoring again. A small sensor measures glucose in the fluid beneath the skin and sends readings to a receiver, pump, or smartphone. Instead of seeing one number from one moment, users can view trends, direction arrows, overnight patterns, and alerts for predicted highs or lows.
A finger-stick result is a photograph. A CGM is more like a movie, complete with plot twists at 2:17 a.m.
CGM data can help users adjust insulin before a problem becomes severe. It can also reveal patterns that might otherwise remain invisible, such as overnight hypoglycemia, delayed glucose rises after high-fat meals, or repeated spikes during stressful meetings.
Automated Insulin Delivery: Toward an Artificial Pancreas
The combination of a CGM, an insulin pump, and a control algorithm produced one of the most important recent advances in diabetes technology: automated insulin delivery.
These systems receive glucose readings from the CGM and automatically increase, decrease, or pause insulin delivery based on predicted glucose levels. Some can deliver automatic correction doses when glucose is expected to rise too high.
Users still perform important tasks, including changing sensors and infusion sites, responding to alerts, and often entering carbohydrate information for meals. The technology is therefore sometimes described as a hybrid closed-loop system rather than a fully autonomous artificial pancreas.
Even with those limitations, automated delivery can reduce the number of decisions a person must make every day. It may improve time spent in the target glucose range, reduce overnight lows, and ease some of the mental burden of constantly calculating, checking, correcting, and worrying.
The technology is also expanding beyond type 1 diabetes. In 2024, the FDA cleared an automated insulin-dosing technology for adults with type 2 diabetes, signaling that connected insulin systems may benefit a broader population.
How Insulin Changed Type 2 Diabetes Care
Insulin is essential from diagnosis for people with type 1 diabetes, but its role in type 2 diabetes is more varied. Many people initially manage type 2 diabetes through nutrition, physical activity, weight management, and non-insulin medications. Because type 2 diabetes can progress, the pancreas may eventually be unable to produce enough insulin.
At that point, basal insulin, mealtime insulin, or a combination may be added. Insulin is also used when glucose is extremely high, during hospitalization or serious illness, around some surgical procedures, and in certain pregnancies.
Modern care increasingly rejects the outdated idea that starting insulin represents failure. Type 2 diabetes is a biological condition, not a report card. Needing insulin does not mean a person has been “bad”; it means the treatment plan needs to match what the body currently requires.
Newer non-insulin medicines have changed when and how insulin is introduced, but insulin remains one of the most powerful tools for lowering glucose when it is genuinely needed.
The Work Insulin Has Not Finished
Insulin’s history is triumphant, but the modern story contains uncomfortable contradictions. Scientists have created remarkably precise formulations and sophisticated delivery systems, yet affordability, insurance coverage, training, and supply access remain serious barriers.
A vial that exists but cannot be obtained might as well be sitting on the moon. People who ration insulin can develop severe hyperglycemia, DKA, hospitalization, permanent injury, or death. Safe care also requires access to needles, pump supplies, glucose meters, test strips, CGM sensors, clinical support, and diabetes education.
Biosimilar insulin products may increase competition and treatment options. In 2025, the FDA approved the first rapid-acting insulin biosimilar in the United States. However, regulatory approval alone does not guarantee that every patient will experience lower out-of-pocket costs or straightforward access.
Health equity therefore belongs in any honest account of insulin’s progress. The next century of diabetes care must be judged not only by what technology can do, but by how many people can safely benefit from it.
Experience After the Breakthrough: What Living With Modern Insulin Can Feel Like
The impact of insulin is easiest to understand through the ordinary experiences it makes possible. A child diagnosed with type 1 diabetes today may leave the hospital with insulin, glucose-monitoring equipment, an emergency glucagon prescription, and a detailed education plan. The family will still feel frightened, but the conversation is about learning to manage the conditionnot preparing for an inevitable decline.
The first weeks can feel like an advanced mathematics course scheduled during an emotional earthquake. Families learn carbohydrate counting, correction factors, basal rates, ketones, exercise adjustments, sick-day rules, and the difference between a glucose reading that requires attention and one that requires urgent help. The refrigerator suddenly contains insulin next to the orange juice, while kitchen scales and nutrition labels acquire starring roles.
Over time, much of this knowledge becomes routine. A teenager may check a CGM before soccer practice and reduce insulin to prevent a low. A college student may carry backup supplies to class. An adult may adjust a dose before a restaurant meal whose carbohydrate count is largely an act of optimism. A parent may follow a child’s CGM readings remotely during the school day and finally breathe normally after seeing a stubborn downward arrow level off.
Technology can reduce uncertainty, but it may also create new forms of fatigue. Pumps beep. Sensors fail during vacations. Adhesive loosens five minutes after swimming begins. Phones lose connections at the exact moment their owners would strongly prefer them not to. Data can be empowering, yet watching every glucose fluctuation may also make a person feel as though the body is being graded continuously.
Insulin decisions are rarely based on food alone. Stress hormones may raise glucose. Exercise can lower it immediately or hours later. Illness can sharply increase insulin needs. Menstrual cycles, growth, travel, sleep disruption, medications, and temperature can all influence patterns. A dose that worked beautifully yesterday may behave like it has never met the patient before.
Modern insulin care therefore involves judgment as well as technology. The person using insulin becomes the leading expert on how diabetes behaves in that particular body. Clinicians contribute medical knowledge, device reports, and treatment recommendations, but day-to-day experience supplies information that no laboratory test can fully replace.
There are also victories that rarely appear in clinical charts: completing a marathon without a dangerous low, sleeping through the night after starting automated delivery, sending a child to camp, navigating pregnancy safely, taking a long flight, or enjoying a meal without allowing diabetes to dominate the conversation.
These experiences show both sides of insulin’s legacy. The medication makes life possible, but it demands attention every day. New devices may reduce the workload, but they do not remove it. The goal of future innovation should therefore be broader than producing better glucose numbers. It should give people more time, more confidence, fewer interruptions, and a life in which diabetes occupies less mental space.
Conclusion: From Rescue Treatment to Connected Care
Insulin’s first achievement was survival. Everything that followedpurified animal insulin, recombinant human insulin, rapid- and long-acting analogs, disposable syringes, pens, pumps, home meters, CGMs, and automated deliverymade that survival safer, longer, and more compatible with everyday life.
More than 100 years after the Toronto experiments, insulin remains indispensable. It has allowed generations of people with diabetes to live lives that would once have been medically unimaginable. Yet its success also creates a responsibility: lifesaving treatment must be affordable, available, understandable, and supported by high-quality care.
The next breakthrough may involve smarter insulin, fully automated delivery, beta-cell replacement, immune therapy, or a genuine cure. Until then, insulin remains one of medicine’s greatest transformationsa small hormone carrying an enormous century of human possibility.
