The incredible history of insulin, a drug that was discovered almost a century ago

Diabetes, a group of conditions in which the body can't properly regulate blood sugar, affects roughly 30 million people in the US.

And for many people living with diabetes - including the 1.25 million people in the US who have Type 1 diabetes - injecting insulin is part of the daily routine.

Insulin, a hormone that healthy bodies produce, has been used to treat diabetes for almost a century, though it's gone through some modifications.

In the past decade, the list prices of insulin have risen about 300%. This has drawn criticism from patients having to pay the high cost as well as from political figures such as Senator Bernie Sanders, who went after insulin drugmakers this month over their exorbitant prices.

Here's the story of how the critical diabetes medicine became what it is today.