Diabetes was first described over 3,500 years ago in ancient Egypt, though it took centuries of observation, experimentation, and breakthroughs before anyone understood what actually caused the disease. The full story stretches from physicians tasting urine to a dramatic dog surgery in 1889 to the Nobel Prize-winning isolation of insulin in the 1920s.
Ancient Descriptions of a Mysterious Illness
The earliest known reference to diabetes-like symptoms appears in the Ebers Papyrus, an Egyptian medical text dating to around 1552 BC. It described a condition involving frequent urination and weight loss, and it included an herbal remedy for “too plentiful urine” using desert dates. The physicians who wrote it had no idea what was happening inside the body. They just knew some people wasted away while urinating constantly.
The word “diabetes” itself came later, from the Greek physician Aretaeus of Cappadocia in the second century AD. He described the disease as a “melting down of flesh and limbs into urine,” capturing the devastating weight loss that marks uncontrolled diabetes. But the critical addition to the name came in 1674, when English physician Thomas Willis tasted the urine of diabetic patients and noticed it was sweet, almost like honey. He added “mellitus,” from the Latin word for honey, to distinguish sugar-laden urine from other causes of frequent urination. Willis also made a surprisingly modern suggestion: that the sweetness first appears in the blood, not the urine.
From Urine Tasting to Chemical Tests
For centuries, tasting urine was genuinely how physicians diagnosed diabetes. That changed in the mid-1800s, when chemists began developing ways to detect glucose in urine without putting it in their mouths. The real breakthrough came in 1908, when Stanley Benedict created a copper-based reagent solution that changed color in the presence of glucose. Benedict’s solution, with minor modifications, remained the standard test for over 50 years.
In 1945, the process became simpler with a product called Clinitest, a tablet that heated urine and produced a color proportional to the amount of sugar present. Then in 1965, the first blood glucose test strip was developed, using an enzyme that reacted specifically with glucose. By the 1970s, the first glucose meters appeared, and by 1980, patients could read digital glucose values at home. These advances, combined with A1C testing (which measures average blood sugar over months rather than a single moment), transformed diabetes from a disease diagnosed by symptoms into one caught early through routine screening.
The Pancreas Experiment That Changed Everything
For most of history, nobody knew which organ was responsible for diabetes. That changed in 1889 through an experiment by Oskar Minkowski and Joseph von Mering in Strasbourg. The two physicians were debating the role of the pancreas in digestion when Minkowski decided to settle the argument by surgically removing a dog’s pancreas entirely. The next day, the dog developed severe diabetes: sugar flooded its urine, it drank water constantly, grew weak, and lost weight rapidly. Minkowski repeated the procedure on three more dogs, all of whom developed diabetes. He was careful to document that no other organs were damaged during surgery, proving the pancreas was the key.
This was a pivotal moment. Before 1889, diabetes was considered a kidney disease because the most obvious symptom was sugary urine. Minkowski’s experiments proved the problem started in the pancreas, not the kidneys, and redirected the entire field.
The Cell Clusters Nobody Understood
Twenty years before Minkowski’s dog experiments, a young German medical student named Paul Langerhans had noticed something odd while examining pancreatic tissue under a microscope. In 1869, he described clusters of small, irregularly shaped cells scattered throughout the pancreas, each cluster measuring a fraction of a millimeter across. He called them “zellhaufen,” or cell heaps. But Langerhans had no idea what they did. He specifically declined to speculate on their function in his thesis.
It took decades for other researchers to connect these cell clusters (eventually named the islets of Langerhans in his honor) to diabetes. By the early 1900s, scientists suspected these islets secreted some substance into the blood that controlled sugar levels. The challenge was extracting it. The pancreas is packed with powerful digestive enzymes, and every attempt to isolate the mysterious substance from the islets ended with those enzymes destroying it before researchers could test it.
Banting, Best, and the Race to Isolate Insulin
Frederick Banting, a Canadian surgeon with no research experience, came up with an idea in November 1920 after reading about the pancreas. He proposed tying off the pancreatic ducts in dogs, which would cause the digestive tissue to wither away while leaving the islet cells intact. In theory, this would let him extract the sugar-controlling substance without it being destroyed.
Banting brought the idea to John Macleod, a diabetes researcher at the University of Toronto, who gave him lab space and a medical student assistant named Charles Best. Through the summer of 1921, Banting and Best performed their experiments: tying off pancreatic ducts, waiting for the digestive tissue to degenerate, then preparing a liquid extract from what remained. When they injected this extract into diabetic dogs, blood sugar dropped. For the first time in history, someone had controlled diabetes with a substance from the pancreas.
They reported their results to the American Society of Physiology in December 1921. But the extract was crude and unreliable. A clinical biochemist named James Collip then developed a more practical extraction method using alcohol to purify the hormone from beef and pork pancreases, which proved far more effective than Banting’s duct-tying technique.
The First Human Patient
On January 11, 1922, Leonard Thompson, a 14-year-old boy dying of diabetes at Toronto General Hospital, became the first person to receive an injection of pancreatic extract. The initial dose of 15 milliliters, prepared by Banting and Best, was a disappointment. It barely lowered his blood sugar and caused an allergic reaction at the injection site. Twelve days later, on January 23, Thompson received Collip’s purified version. This time, his blood sugar normalized, the sugar disappeared from his urine, and his symptoms improved dramatically.
Thompson lived another 13 years on insulin injections, dying at age 27 from long-term complications of diabetes. His case proved that diabetes, previously a death sentence, could be managed. Word spread fast. Within months, patients across North America were receiving insulin.
A Nobel Prize and a Lasting Controversy
In 1923, Banting and Macleod were awarded the Nobel Prize in Physiology or Medicine. The decision immediately sparked conflict. Banting was furious that Macleod, who had provided the lab but not performed the experiments, shared the prize instead of Best. He split his prize money with Best. Macleod, in turn, split his with Collip.
The controversy ran even deeper. Several European researchers had produced pancreatic extracts with antidiabetic effects years earlier. Eugène Gley in France had documented similar work in 1900. Georg Zülzer in Berlin created an extract called “acomatol” in 1908. And Romanian physiologist Nicolae Paulescu had published results with his own extract, “pancreine,” in 1920, before Banting even began his work. All of these extracts contained the same active substance. The Nobel Foundation eventually revised its description of the 1923 award, changing the language from “the discovery of insulin” to credit for “having produced the pancreatic hormone in a practical available form.” What set the Toronto team apart was not discovering insulin’s existence but making it usable for patients.