On top of a healthcare system with ever-growing medical debt, a new report indicates that most Americans are unaware they can challenge some of their unexpected medical bills.

According to a new survey from the Commonwealth Fund of a nationally representative sample of 7,873 US adults, 45% of respondents between the ages of 19 and 64 reported challenging a bill for a service that they thought should have been free or covered by their health insurance.

Among the 55% who did not challenge their bills, 54% were unaware they had the right actually to do so. Other reasons cited include being unsure of who to contact, lacking the time to reach out, and viewing the amount as too small to be worth the challenge.

“Getting a bill and not being certain whether it’s an error or if your plan should have covered it, and then the complexity of following up about a bill, not knowing who to contact, not even knowing if you have a right to challenge a bill — it points to considerable complexity in our health insurance system and people’s lack of clarity, both about their own benefit plans and what to do when they have questions about care that they get through those plans,” Sara Collins, senior scholar of healthcare coverage and access at the Commonwealth Fund, told Yahoo Finance.

'Helping people be aware of their rights'

Under the Affordable Care Act, all insurers — both private and public — are required to cover preventive services free of charge. The law also grants people the right to appeal insurance decisions, regardless of what type of insurance they have. However, that information isn’t easily accessible for many consumers.

For individuals who have challenged their bills, 38% saw those bills either reduced or eliminated.

According to Collins, there are a few steps that the healthcare system could take to ease the burden on consumers.

“One is greater consumer awareness and support,” she said. “There are some states that have consumer assistance plans that help provide phone numbers that people can call when they have coverage denial. So just helping people be aware of their rights and the processes to appeal insurance decisions.”

Another move, Collins said, is to increase the federal monitoring of claims denials.

Departments could “more closely monitor rates of claim denials, looking at insurers that have high rates of denials,” Collins said. “On the billing dispute part, I think that a reduction in plan complexity would help a great deal.”

Younger adults between the ages of 19 and 34 and Hispanic/Latino adults were the most likely to not challenge their bills, with a majority stating they didn’t know they had the right to do so.