January 10, 2023

World Insulin Day Celebrates J.J.R. Macleod, Scottish Co-Discoverer of Insulin

A new awareness day inspired by the legacy of renowned Scottish physiologist John Macleod launches on 23 January, the anniversary of the world’s first successful dose of clinically useful insulin for the treatment of Type 1 diabetes.


“Our goal for this day is to raise awareness of Professor Macleod, who expertly led the University of Toronto team that discovered insulin,” says John Otto, Founder and Chairman of the JJR Macleod Memorial Statue Society in Aberdeen. “An equally important goal of World Insulin Day is to set the record straight about the exact date this medical breakthrough happened.”

John Otto, Founder and Chairman of the JJR Macleod Memorial Statue Society

On 23 January 1922, Canadian teenager Leonard Thompson was given the first dose of purified Toronto insulin. Within hours, his physical condition and tests improved dramatically, signalling the team’s success in isolating and preparing the long-sought, life-saving treatment for diabetes. Prior to this, people with what is now known as Type 1 diabetes typically survived only a matter of months from diagnosis.

The injection on 23 January was actually Thompson's second dose of pancreas extract, as the first dose was unsuccessful. Prepared by team members Frederick Banting and Charles Best and administered on 11 January, the initial extract had only a marginal effect on urinary glucose and its impurities caused an adverse reaction at the injection site.

A more purified version of insulin, prepared by James Collip using a method suggested by Macleod, was injected 12 days later and worked sensationally. All Thompson’s symptoms disappeared and he lived another 13 years before dying of pneumonia. Today, more than a century after history was made on 23 January 1922, this “miracle treatment” has saved tens of millions of lives around the globe.

Insulin was one of the most important medical advances of the 20th century and Frederick Banting and John Macleod shared the 1923 Nobel Prize for Medicine or Physiology. Despite this, Macleod’s instrumental role as the hugely experienced and accomplished leader of the University of Toronto laboratory has been almost entirely overlooked; instead, the discovery of insulin is frequently and inaccurately attributed only to “Banting and Best”.

J.J.R. Macleod,  Scottish Co-Discoverer of Insulin

“The fact that Macleod continues to be ‘air brushed from history’ is a source of great frustration to anyone who knows the genuine story of the discovery of insulin,” says Mr Otto, who has lived with Type 1 diabetes himself for nearly 50 years. “It’s equally frustrating that 11 January is often cited as the date of the first successful use of insulin, when in truth it was the 23rd of the month.  

“We consider it rather an injustice that World Diabetes Day is celebrated each November on Banting’s birthday. As meticulously laid out in Michael Bliss’s 1982 book, The Discovery of Insulin, Banting’s fabled ‘great idea’ had been abandoned for some time before the team came up with the winning formula. An awareness day marking the date of the true Toronto breakthrough – credited to the combined efforts of Banting, Best, Collip and most of all Macleod – is long overdue.”

In addition to World Insulin Day, the 100th anniversary of Professor Macleod’s Nobel Prize will be celebrated in Autumn 2023, when a bronze and granite memorial honouring the Scottish scientist is to be unveiled in Aberdeen, the city he called home for many years.