On the 11 January 2022, 100 years ago, 14-year-old boy Leonard Thompson was the first person in the world to receive an insulin injection to treat type 1 diabetes. Insulin was first extracted in the fall of 1921 by physiology professor Frederick Banting, from cows pancreas, and within a few months it was ready for testing. The first injection was so impure that it cause of Leonard severe allergic reactions, and further injections had to be suspended until the extract was purified enough to cancel the side effects. The cure was a success: before insulin was available to patients, type 1 diabetes was a death sentence, within months or even weeks. Leonard Thompson considerably improved his health and lived until age 26; he did not die of diabetes, but of pneumonia.
Archives Portal Europe holds a considerable collection on insulin, check some of the results at this link: http://www.archivesportaleurope.net/search/-/s/d/1607