Medical Bills Catch Almost Half of Insured US Adults by Surprise

Forty-five percent of US adults say they’ve been billed in the past year for medical care that they thought was covered by their insurance, leaving many footing the bill for insurance-company errors.

Less than half of those who received surprise bills wound up challenging them, according to a report Thursday from the Commonwealth Fund, an independent health research foundation. Many who didn’t challenge say that’s because they weren’t aware it was an option or feared it wasn’t worth their time.

While US workers and their employers together pay about $24,000 a year for family health insurance premiums, the diversity of ...