The incredible history of insulin, a lifesaving diabetes drug that was discovered almost a century ago and is now at the center of drug pricing outrage

• 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. 
• Visit BusinessInsider.com for more stories.

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. 

SEE ALSO: The strange history of the EpiPen, the device developed by the military that turned into a billion-dollar business

DON'T MISS: Everyone wants a piece of the drug industry, and it's one reason prices are rising so fast

Insulin is an integral part of the human body. It's a hormone that's produced in the pancreas to help regulate our blood sugar levels. For those living with Type 1 diabetes, the pancreas doesn't make any insulin, which can cause blood sugar levels to rise too high.

In the 1920s, researchers figured out that the pancreas was an important part of what was making diabetics so sick and got to work figuring out if they could make a treatment. Pictured here is an inflamed pancreas alongside other organs, from a rhesus monkey.

Dr. Frederick Banting, a Toronto-based surgeon, along with medical student Charles Best, started by testing out what happens when you remove a dog's pancreas. When they did, the dog developed diabetes. Next, they found that if you inject insulin back into the dog, it went back to normal.