January 11th 1922 is a very important day in the history of diabetes. On this day, the insulin was first used in the treatment of diabetes.

January 11th 1922 is the day when the lives of people with diabetes changed
A fourteen-year-old Leonard Thompson, who had diabetes, was dying at the Toronto General Hospital. The doctors gave him the first injection of insulin – a pancreatic extract prepared by Dr. Frederick Banting, and medical student, Charles Best. However, the extract was so impure that Thompson suffered a severe allergic reaction.
Over the next 12 days, James Collip worked day and night to improve the ox-pancreas extract. On the 23rd of January, they injected him a second dose of insulin. Luckily, this was completely successful. The boy’s blood sugar levels dropped to normal levels. Thompson would live another 13 years with daily injections of insulin, before dying of tuberculosis.
A dramatic moment
Doctors kept the children dying from diabetic ketoacidosis (DKA) in large wards, often with 50 or more patients in a ward, mostly comatose. Grieving family members were often in attendance, awaiting the (until then, inevitable) death. In one of medicine’s more dramatic moments Banting, Best, and Collip went from bed to bed, injecting an entire ward with the new purified extract. Before they had reached the last dying child, the first few were awakening from their coma, to the joyous exclamations of their families. Although it was not a cure, it was a monumental breakthrough in treatment for diabetes.
Published paper in the Canadian Medical Association Journal
In March 1922, the Canadian Medical Association Journal published a paper in which described the case of Leonard Thompson, and six other patients the Banting and Best team treated with the refined extract. Additionally, this was the first official announcement of an extract developed to alleviate the symptoms of diabetes.
“A message of hope to sufferers from diabetes goes out authentically today from the medical research laboratories of the University of Toronto. The modesty of medical men and scientific investigators of the genuine brand attempts to minimize the results obtained. The harm of exaggeration and the injustice to both parents and research men in awakening false and premature hopes before the extracts can possibly be manufactured cannot be over-emphasized. But the fact remains that one of the most important discoveries in modern medical research has been made at the university here. It is not a cure for diabetes, its authors state. Within six months, however, their discovery will be used on a large scale, they hope, to prolong life quite considerably at least. There will be no secrecy, as from the beginning. The medical profession will know all the facts.”
— The Toronto Daily Star – March 22, 1922 Edition