The share of Americans with unpaid medical bills tainting their credit files has fallen in the two years since the major credit reporting agencies — Equifax, Experian and TransUnion — changed how that debt was reported, a federal watchdog agency said this week.

But even with the changes, some 15 million people — many of them living in low-income communities and in the South — still have medical bills in their credit files, the Consumer Financial Protection Bureau reported. Rohit Chopra, the bureau’s director, said in a statement that “further reforms” were needed to scour medical debt from credit histories. The bureau is considering a rule to ban medical debt from consumer credit files.

The bureau estimated in a 2022 report that well over half the debt that appeared on credit reports as being in collection was medical debt. Having unpaid medical bills on your credit report can make it hard to qualify for loans and credit cards, get cellphone service, rent an apartment or even secure a job, since landlords and employers also check applicants’ credit history.

Yet the bureau’s research suggests that medical debt is a less useful measure of a borrower’s creditworthiness than other types of debt, largely because of the complexities of the American health care system. People can incur medical bills unexpectedly, and many think that their health insurance will cover the costs. They often must contact insurers, hospitals or doctors and may end up haggling over their correct share of the bill. And the consumer bureau previously found that medical collection debt reported to the credit bureaus was “plagued by inaccuracies.”

“There’s a lot of back and forth,” said Breno Braga, a principal research associate at the Urban Institute think tank and a co-author of a recent report on medical debt. “You don’t see that with any other type of debt.”

In 2022, amid scrutiny from the consumer bureau, the three major credit reporting agencies voluntarily adopted changes in how medical bills were included in credit files. They agreed to exclude any medical collection debts that had been paid and those that were less than a year old, allowing for time to clarify a patient’s responsibility for the bill. And as of April 2023, the credit bureaus stopped including any medical collections for amounts under $500. (Hospitals and doctors send unpaid bills to collection agencies, which may then report them to the credit bureaus.)

The changes had an effect: About 5 percent of Americans had unpaid medical bills on their credit reports last June, down from 14 percent in March 2022, the consumer bureau found. Older Americans benefited the most, with 3 percent having medical collections on their credit reports last June, down from 14 percent.

The credit reporting bureaus said there was no need for the federal government to further restrict the reporting of medical bills. “We believe what’s been done is enough,” said Eric J. Ellman, senior vice president for public policy and legal affairs at the Consumer Data Industry Association, which represents the credit bureaus.

Medical bills remaining on credit reports are larger on average than they used to be. (Because smaller debts have been eliminated from reports, the average debt has risen to more than $3,000 from $2,000.) If a consumer applies for a mortgage or car loan, Mr. Ellman said, the lender taking the risk should know if the borrower has significant medical debt.

Diane Thompson, a senior adviser to Mr. Chopra, said in an interview that removing medical debt from credit reports eliminated the “coercive” aspect of bill collections. Often, she said, “they are put there to enable debt collectors to collect bills that may or may not be accurate.”

Ms. Thompson also noted that the current changes to medical debt reporting were voluntary, and that the industry could revoke them at any time.

Mr. Braga of the Urban Institute noted that removing medical debt from credit reports didn’t mean that the debt itself had gone away. In most states, hospitals and medical providers can still take patients to court to collect it.

There could also be unintended consequences to removing all medical debt from credit reports, he said. Health care providers, for instance, could potentially demand payment upfront for services if they worry that they won’t be able to collect the money later. Or they could increase their promotion of medical credit cards, which can add interest costs to patients’ bills.

Here are some questions and answers about medical debt and credit reports:

Why do so many Americans have medical debt?

Medical debt is a persistent problem even though over 90 percent of the U.S. population has some type of health insurance, according to a report from the Peterson Center on Healthcare and KFF, a health care research group. High deductibles — the amount patients must cover out of pocket before insurance pays — mean that some people can’t afford the cost of care even if they are insured. KFF polls show that people with medical debt report cutting back on food, clothing and other essentials to pay medical bills. People with chronic illnesses or cancer may have medical costs that compound over time. People with cancer, for instance, have higher levels of debt than people who have never had the disease.

Do some states bar the reporting of medical debt to credit bureaus?

At least two states have taken steps to keep medical debt off credit reports. Last year, Colorado became the first state to bar the inclusion of medical debt on credit files, followed by New York.

How can I check if my credit report contains medical debt?

You can check your online credit reports from the three major bureaus without charge each week at AnnualCreditReport.com. But some consumers have struggled to use the website, said Ryan Reynolds, a financial policy analyst with Consumer Reports. A recent survey of about 4,300 volunteers recruited by Consumer Reports and WorkMoney, a nonprofit that aims to help consumers improve their financial lives, found that 11 percent of participants who were able to check their credit file reported difficulty getting their reports, mostly because of technical difficulties or problems with outdated identity verification information.

“It’s clunky,” said Carrie Joy Grimes, the chief executive of WorkMoney. (A quarter of the initial participants were unable to obtain their reports; some couldn’t get past security questions, while others got error messages.)

Consumer Reports and WorkMoney have asked the credit bureaus, which sponsor the website, to make it easier for consumers to use.

In an emailed statement, the Consumer Data Industry Association said, “The consumer reporting industry shares the same goal as consumers, advocates and regulators when it comes to credit reports: They should be accurate and complete.”

Almost half the volunteers in the survey found errors in their reports, and about a quarter found “serious” errors that could harm their creditworthiness, like late or missed payments that they knew had been made on time or debts that were reported as being sent to collection but that did not belong to them.

If you do find an error on your credit report, Mr. Reynolds recommends filing a dispute on paper. Make copies of account statements and other documents to create a paper trail and send them by certified mail, with a receipt requested, to each of the three credit agencies. (Keep copies for yourself.) If you don’t get a resolution that way, he said, file a complaint with the Consumer Financial Protection Bureau.