Health care deductibles and out-of-pocket expenses are so high for nearly one-fourth of the insured population that they are considered underinsured, according to a new study from The Commonwealth Fund.

The health insurance survey found that an estimated 31 million insured Americans are not adequately protected against high health care costs, a number that has doubled since 2003.

"Someone who is underinsured does have health insurance, but with coverage that does not protect against high health costs relative to income," said David Blumenthal, president of The Commonwealth Fund.

The 22-page report identified rising deductibles as the biggest problem for those considered underinsured, which continues to be an issue even under the new Obamacare program.

"The steady growth in the proliferation and size of deductibles threatens to increase underinsurance in the years ahead," the report warns, according to The Hill.

Even though millions of people are paying into the system, most are unable to reap the benefits, the survey found.

The report also mentions how high out-of-pocket costs associated with the lowest-quality health insurance plans dissuade policyholders from seeing the doctor when they are hurt or injured.

Half of underinsured respondents and 41 percent of privately insured respondents with deductibles of $1,000 or higher had medical bills totaling $4,000 or more, according to the report.

"The financial and health insecurity that comes from being underinsured is substantial and puts people's health and well-being at risk," Blumenthal said. "If health insurance costs continue to be shifted to consumers at the rates we have seen over the past 10 years, the problem will likely grow."

Such findings call into question President Obama's promises that his health care reform would provide millions of Americans with affordable health insurance. Although, the report doesn't account for people who didn't have insurance before 2014, The Hill notes.

"We're unable to separately assess the effects of the law with these data," said Sara Collins, the study's lead author. "What we're seeing, though, in the data is ever-growing deductibles."