Rising prices for insulin are getting scrutiny from diabetes patients, physicians and politicians.

More than 7 million Americans with diabetes need insulin to control their blood sugar and stave off dangerous complications. The average price of insulin tripled between 2002 and 2013, according to the American Medical Association. The group recently called on regulators to monitor competition among the three drugmakers who control the market.

Meanwhile, several congressional lawmakers are probing the multibillion dollar insulin market.

Drugmakers generally blame higher prices on health care middlemen who they say drive up prescription costs. Some drugmakers have pledged to limit their annual increases and also offer assistance to lower-income patients.

The Associated Press spoke with diabetes specialist Dr. Robert Lash, an executive with the Endocrine Society, about insulin prices. The questions and answers have been edited for clarity and length.

Q: How long has insulin been used to treat diabetes?

Purification of insulin was a major historical event and it happened about 100 years ago. Initially, it came from animals. And then in the 1990s, recombinant DNA technology was available so we could make and purify human insulin in bacteria and that became the source of insulin.

Then people realized they could make insulins with different properties by making small genetic alterations — insulins that act more quickly or more slowly. Those are the insulins that are now the subject of the price increases we’re seeing.

If you look at what’s called regular insulin, you can get that at a pharmacy for $25 to $30 per vial. And if you look at the same insulin with one tiny amino acid change that insulin is $300 a vial.

Q: What accounts for that price difference?

You have asked the question that everyone keeps asking. These insulins have been around for 20 years, they’re made pretty much the exact same way in the exact same factories. What other manufactured product do you know that shows no economies of scale and no price drop in 20 years? TVs, phones, cars get cheaper — but insulin never does.

And the reason it doesn’t is that it’s a medicine that everybody needs and it has an incredibly complicated supply chain where every player is trying to maximize their own profit.

Q: How do these prices impact patients?

A: When patients don’t have insurance and can’t afford their insulin, bad things can happen. They may use less insulin than they should and their glucose isn’t well controlled so they are more likely to have complications of diabetes.

Q: How are doctors responding?

A: There is a movement among some endocrinologists to go back to older forms of insulin because they are so much cheaper. They wouldn’t be for everybody, but there are probably a lot of people who could use the older insulins. The trouble is that these newer insulins have been around so long that we have multiple generations of physicians who have never used the older insulins before.

(AP)