Nearly half of insured Americans get surprise expenses in medical bills, study finds

Nearly half of insured Americans have been smacked by surprise medical expenses in the past year, but a majority don't contest billing errors or coverage denials, a new survey by the Commonwealth Fund finds. 

That inaction — which largely stems from an unawareness that such bills and denials can be challenged — can be a costly, as the effort frequently works, according to the study published on Thursday by the nonprofit private foundation.

Forty-five percent of 7,873 insured adults surveyed nationwide relayed being billed for a service they thought should have been covered, the Commonwealth Fund found. Nearly one in five — or 17% — reported being denied coverage for a doctor-recommended service.