Eli Lilly first mass-produced insulin commercially in 1923.
The company began manufacturing insulin after Frederick Banting and Charles Best's work at the University of Toronto showed that pancreatic extracts could treat diabetes. Lilly collaborated with the Toronto researchers and helped develop a reliable large-scale production process.
Insulin had been discovered only a short time earlier, so commercial manufacturing quickly changed diabetes from a frequently fatal disease into a condition that could be managed for many patients. Lilly's early product was known as Iletin.
The discovery is often linked only with Banting and Best, but the wider achievement also involved John Macleod, James Collip, and industrial manufacturing expertise. Eli Lilly remains a major pharmaceutical company, with a portfolio extending far beyond insulin.