WASHINGTON — Having trouble getting in to see a doctor?

You’re not alone.

Tens of millions of adults under age 65 — those with insurance and those without — saw their access to health care worsen dramatically over the past decade, according to a study abstract released Monday.

The findings suggest that more privately insured Americans are delaying treatment because of rising out-of-pocket costs, while safety-net programs for the poor and uninsured are failing to keep up with demand for care, say Urban Institute researchers who wrote the report.

Overall, the study published in the journal Health Affairs found that one in five American adults under 65 had an “unmet medical need” because of costs in 2010, compared with one in eight in 2000. They also had a harder time accessing dental care, according to the analysis based on data from annual federal surveys of adults.

“For decades, Americans have been facing costs rising well above wage levels,” said Lynn Quincy, senior policy analyst for Consumers Union, a nonpartisan group. “These are real families. … It’s very concerning.”

The 2010 health care law, which will expand health coverage to 30 million people starting in 2014, won’t necessarily solve all those access problems, the study said. That’s because the law, which is under review by the U.S. Supreme Court, may not alter the trend toward private insurance policies with larger deductibles and higher co-payments or address some of the barriers within public coverage.

The study underscores what’s at stake in the law’s coverage expansion: People with private or public health insurance have significantly better access to care than the uninsured. If the law is overturned or scaled back, “we would be likely to see further deterioration in access to care for all adults — uninsured and insured alike,” it concludes.

The percent of adults with private insurance who reported an “unmet medical need” doubled to 10 percent from 2000 to 2010, while those who delayed seeking care because of cost rose from 4 percent to 7 percent in the same period, according to the study.

One analysis by the consulting firm Milliman showed health costs for an American family of four have more than doubled since 2002.

“As employers shift more costs onto workers, that is something we are going to continue to see,” Cunningham said.

For insured Americans, a shortage of doctors in some parts of the country was a factor, but not as important as cost, he said.

An increasing number of consumers are also facing delays finding a primary care doctor when they are sick because physicians leave less room on their schedules for walk-ins, said Arthur Kellermann, director of the research firm RAND Health.

Poor and uninsured adults had greater difficulties not just with health care costs, but finding doctors who would see them.

About one-third of 41 million uninsured adults delayed getting care because of costs in 2010, compared with 25 percent in 2000, the study found. Nearly half the uninsured said they had an unmet medical need in 2010, up from 33 percent in 2000.

The uninsured who had a “usual source of care,” such as a family doctor or community health center, fell to 38 percent in 2010 from 44 percent in 2000. The finding was startling, given the billions in additional federal funding that went to community health centers over the past decade, Cunningham said.

Toni Wolf, 45, of Roanoke, Va., says she has put off going to the doctor for the past year, even though she has diabetes and suffers from a lung disorder that causes her to be short of breath. “It makes me feel very stressed and worried,” said Wolfe, who works as a teacher at a day care center but can’t afford the employee coverage it offers.RAND’s Kellermann noted that even as the nation’s total health care bill doubled in the past decade to $2.6 trillion, many Americans had difficulty getting treated.

“We’re paying more and more and getting less and less,” he said.