Injectable insulin has soared in price in the last few years, hitting diabetics with sticker shock.

Express Scripts, the largest U.S. pharmacy-benefit manager, said the price of two prominent brand-name injectable insulins, Lantus and Humalog, rose nearly 23 percent and about 20 percent, respectively, from 2014 to 2015, Medical Express reports.

Manufacturers defended the increases, saying research for future medicines involves some failures, which still must be paid for, and that recent changes in insurance plans mean patients have to pay more.

"This means someone who previously paid $25 to $40 copay for a medicine could now face 'list price' costs of hundreds of dollars for a prescription until they meet their higher deductible," said Eli Lilly & Co. spokesman Greg Kueterman said in a statement.

"Every day, we negotiate with health plans, pharmacy-benefit managers, and other intermediaries to make sure our medicines are accessible for as many people as possible," Novo Nordisk spokesman Ken Inchausti said in a statement.

But like other brand-name drugs, insulins have patent protection and slices of market exclusivity, which allows manufacturers to push for higher prices. In 2014, Sanofi got $6.93 billion in revenue from its long-acting insulin, Lantus, the best-selling brand.

Insulin helps the body break down sugar and use it. But Type 1 diabetics produce no insulin. Without injections of it — via syringe, pen, or pump — death can occur in days or a few weeks.