Many Americans still receive unexpected bills or coverage denials and need better health literacy to challenge them, according to an issue brief from Commonwealth Fund. Investigators found, in a survey of more than 5,600 insured adults, that 45% of participants or their family members had received an unanticipated bill or copayment for a service they expected to be free or insured. Among those who received an unexpected bill, only 45% challenged it. The survey also indicated that Medicare beneficiaries (53%), Medicaid plan members (50%), Hispanic individuals (49%), and those with incomes exceeding 400% of the federal poverty level were most likely to challenge a bill.