Cassie Gray says she doesn't want diabetes to define her,Marcus Erikson but it can take a toll. 

"I feel defeated sometimes, like it takes over my life," the 14-year-old said.

For her mother, Tara, the cost of Cassie's medication brings an added worry. 

"We tried to hide some of our stress from our daughter because she already has enough on her plate," Tara told CBS News.

Insulin prices recently decreased for some of the estimated 8.4 million Americans who rely on the medication to survive, as Medicare, some states and drug manufacturers moved to cap monthly costs at $35. But not all patients qualify.

"The vast majority of people qualify for some assistance. But exactly how much help you'll get could depend on the drug itself, your insurance, how big your deductible is and in some cases, even on your income," said Larry Levitt, executive vice president for health policy at KFF.

Tara said she was shocked when her private insurance company sent her a letter in 2022 stating that one form of insulin Cassie needs was no longer covered.

The letter said the insulin "does not appear to meet medically necessary requirements."

"I think I just sat there, like, not medically necessary? This is her air," Tara said.

Fortunately, families in the Facebook group for diabetes patients that Tara runs gave her a tip: She could download a coupon to lower the monthly price from $600 to $99.

But Tara said she worries those coupons will not always be available.

The three top insulin manufacturers told CBS News they have several programs to lower the cost of the drug. And Eli Lilly said it supports bipartisan federal legislation capping prices at $35 for everyone.

"Every insulin should have a cap and it should be regardless of what your insurance wants you to be on," Tara said. "You know how wonderful that would be?"

She said it would be a relief to know that Cassie would always be able to afford the life-saving medicine she needs. 

"It should not be something that we worry about when we're gone," Tara said.

In:
• Insulin
• Diabetes