As open enrollment season starts, a new survey is providing an important reminder that you need to look just beyond the cost of a health plan's monthly premium to figure out your expected medical costs for the coming year. With things like deductibles and co-pays creeping higher for nearly everyone, many adults are spending a chunk of their income on out-of-pocket costs.

About 21 percent of privately insured adults said they spent at least 5 percent of their income on medical care (not including the cost of premiums), and 13 percent said they spent at least 10 percent of their income on these out-of-pocket costs, according to the Commonwealth Fund Health Care Affordability Tracking Survey.

This picture looks especially tough for the poor. People earning below the federal poverty line ($11,490 for an individual) were about four times as likely to spend more than 10 percent of their incomes on medical care compared to people earning more than 400 percent FPL, or roughly $46,000 for an individual.

And if you have a chronic condition, you're about twice as likely to spend at least 5 percent or 10 percent of your income on medical expenses.

People participating in the survey, taken from a nationally representative sample of adults, were asked to recall copays for hospital and doctor visits, as well as their spending on prescriptions and vision and dental care in the past year. Commonwealth Fund researchers then calculated those costs as a share of their income.

These costs do have an effect on whether people seek out care, the survey finds. Even about one-fourth of privately insured adults with deductibles less than 5 percent of income said they skipped out on needed care at some point because of their deductible.

Out-of-pocket medical spending has been one of the big issues to watch in the rollout of the Affordable Care Act's coverage expansion. Though the law limits how much a consumer has to pay out-of-pocket each year on care, people enrolled in new ACA marketplace plans are generally still facing higher deductibles compared to employer-sponsored health plans. And even deductibles in employer plans are growing more prevalent, as this year's Kaiser Family Foundation/HRET survey showed. Health plans now, however, are generally required to cover preventive services without cost-sharing.

The rise of high-deductible plans are supposed to help keep down health spending and make people be smarter consumers of their care — for example, maybe they pass up getting an unnecessary test if they're absorbing more of that cost. This becomes problematic, though, if they're skipping truly necessary care because they can't afford it.

This morning's Commonwealth report concludes with this warning: "Cost-sharing in health plans is affecting people’s medical decisions in ways that should be of concern to policymakers and the medical community."