2021 marks 100 years since insulin was first discovered. The World Health Organisation estimates that 422 million people around the world have diabetes, a disease where the body either can't produce enough insulin or doesn't respond properly to insulin. In the UK, 1 in 15 people are affected, and that's only set to rise as more and more of us are overweight or obese. So what is insulin, how was it discovered, and how have we reached a place where millions of people can safely inject themselves with it every day? Sally Le Page explains... Like this podcast? Please help us by supporting the Naked Scientists