Insulin was discovered in 1921, and first successfully used to treat a human in January 1922.

Key dates at a glance

  • 1921: Canadian physician Frederick Banting and medical student Charles Best, working in John Macleod’s lab at the University of Toronto, isolate an internal secretion from the pancreas that becomes known as insulin.
  • 23 January 1922: A 14‑year‑old boy with type 1 diabetes, Leonard Thompson, becomes the first person to receive a successful therapeutic injection of insulin.
  • 1923: Insulin begins to be produced on a mass scale, making it widely available as a life‑saving treatment for diabetes.

So if you’re looking for the simple historical answer to “when was insulin invented,” people usually point to 1921 for its discovery and early 1922 for its first real-life medical use.