Who was the first person treated with insulin for diabetes in 1922?

Leonard Thompson was the first person treated with insulin for diabetes in 1922.

Thompson was a 14-year-old boy at Toronto General Hospital with severe type 1 diabetes. On 11 January 1922, he received an early insulin extract, but the preparation was impure and produced little benefit. A refined extract was given later that month, and his condition improved dramatically.

Frederick Banting and Charles Best had obtained pancreatic extracts in Toronto, while biochemist James Collip helped purify the material enough for clinical use. John Macleod directed the laboratory where the research took place. The discovery changed diabetes from a usually fatal illness into a condition that could be managed with replacement insulin.

Insulin was not the first treatment ever attempted for diabetes, and the 1922 extract was not identical to modern manufactured insulin. Today, insulin is produced in highly purified forms, often using recombinant DNA technology.