For millions of Americans, a trip to the doctor's office or hospital can be a prescription for debt. But who do the estimated 100 million people with medical debt owe?

A new analysis suggests bills for hospital care make up most medical debt in the United States — and that low-income people and people of color are disproportionately affected by overdue medical debt. The report from the Urban Institute drew on data from a June survey of a nationally representative sample of 9,494 adults ages 18 to 64.

Respondents whose incomes were at or below the federal poverty level — $12,880 for an individual and $26,500 for a family of four — reported the most debt, with 26.4 percent overdue on a medical bill. The number fell as incomes rose; overall, 15.4 percent of respondents were past due.

Black and Latino respondents had more debt than their White counterparts; 25.9 percent of Black respondents and 19.1 percent of Hispanic/Latinx respondents were past due, compared with 12.8 percent of White participants.

Nearly three-quarters of the survey respondents who reported having past-due medical debt owed some or all of that debt to hospitals. Of those in the lowest income bracket, 79.7 percent owed hospitals.

Owing a hospital also meant higher amounts of debt across the board — 67.4 percent of respondents who owed non-hospital providers had debts of less than $1,000, while just 28.5 percent who owed a hospital had less than $1,000 to pay. And 26.4 percent who owed a hospital had past-due debt of $5,000 or more.

The majority surveyed said they had been contacted by collection agents about past-due bills. But a disproportionate number of people at or below the poverty line had faced debt-related lawsuits — 7.6 percent for those below the poverty line compared with 4.5 percent for wealthier respondents.

Much of that debt may be due to brief hospital visits. In a 2022 survey, the Kaiser Family Foundation found that 72 percent of adults with medical debt owe because of a one-time or short-term problem such as an emergency department visit.

"We see that individuals with disabilities, and Black and Latino adults are disproportionately represented among adults carrying past-due medical debt," Gina R. Hijjawi, senior program officer at the Robert Wood Johnson Foundation, which partnered with the Urban Institute on the research, said in a statement. "Consumers need standards in place that protect them from undue medical debt and help them obtain affordable care."

The researchers say their findings show the ineffectiveness of federal policies, which provide tax exemptions for nonprofit hospitals provided they give some amount of financial assistance to those who cannot pay for care. According to the American Hospital Association's latest count, about 58 percent of U.S. hospitals are nonprofit institutions.

In a 2022 analysis, the Kaiser Family Foundation found that charity care costs represented 1.4 percent or less of operating expenses of all hospitals in 2020. Medicaid expansion could also help patients, researchers suggest, along with other insurance reforms to reduce or eliminate debt.