Nicole Smith-Holt from Richfield, MN holds a vial with the ashes of her son Alec, who died at the age of 26 from insulin rationing, during a protest against the high price of insulin outside the offices of drug giant Sanofi in Cambridge, MA on Nov. 16, 2018. John Tlumacki/The Boston Globe via Getty Images

For the 1.25 million Americans living with Type 1 diabetes, insulin is a life-saving drug that helps them process the sugar in their blood.

Price increases for insulin have put pressure on people living with diabetes who don't have insurance, or whose insurance plans require them to pay the full price of the medication.

Here's the history of how insulin was discovered and how a treatment discovered almost a century ago became a target of public and political outrage in 2019.

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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 who have to pay the high cost as well as from politicians, who are going after drugmakers over their prices.

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

This article was initially published in 2016 and has been updated.