Medical debt has once again reached unprecedented levels in the US.

According to recent findings from the Peterson-KFF Health System Tracker, an estimated 20 million American adults owe roughly $220 billion in medical bills.

“Medical debt is kind of an interesting thing,” Matthew Rae, associate director of the Program on the Health Care Marketplace at the non-profit KFF, told Yahoo Finance. “Sometimes medical debt is chronic conditions that you're financing over a long period of time, or you have an accident, and then you're fine. But sometimes medical debt is stuff that also hurts your ability to earn money. ... You're taking on huge expenses to pay for your care, and you’ve also got diminished income.”

'A vicious cycle'

KFF's survey indicated that those with medical debt also face a significant impact on their financial well-being. Most adults with unpaid medical bills owe at least $1,000, and 14% owe more than $10,000.

There were also notable disparities across racial and ethnic groups, income brackets, and geographies. Black Americans have the highest percentage of medical debt, at 13%, and the southeastern US — which has a significant Black population — has the highest share of residents with medical debt.

Mississippi had the second-largest share of adults with medical debt, at 15.2%; only South Dakota had a higher share in the US, with 17.7% of its residents in medical debt.

Rae noted that the long-term impact of medical debt contributes to overall inequities in the US.

“The challenging thing to think about with this issue is that ... it ripples through your finances for years and years in ways that we don't always think of when we're thinking about health coverage and uninsurance rates,” Rae said. “There's a lot more going on in how this is all impacting what it means for a household’s ability to collect assets and build wealth over generations.”

For example, 40% of US adults with medical debt stated they borrowed money from a retirement account, compared to just 6% of those without medical debt. Those with unpaid medical bills were also significantly more likely to seek out payday loans, which carry extremely high interest rates, obtain money from selling items to a pawn shop, or take out a loan against their car.

Rae emphasized that the number of people using payday lenders for their medical debt "really hit a chord."

“They just end up in a vicious cycle of seeing their finances in ways which are going to make it hard to acquire assets and build wealth over many years," he reiterated.