About two-thirds of people whose families struggled to pay their medical bills were uninsured. Another 25 percent relied on a public healthcare program, such as Medicaid, and 14 percent had private insurance coverage, according to the CDC's report.
The healthcare law is expected to eventually cover about 24 million people who are currently uninsured. The law expands eligibility for Medicaid and also sets up new marketplaces to buy private insurance — often with a government subsidy.
Of the 54 million people who had problems paying for healthcare last year, 34 percent had family incomes between 100 and 200 percent of the federal poverty limit — meaning they would likely qualify for subsidies under the healthcare law to help cover the cost of their premiums.
Another 14 percent had household incomes above 200 percent of the poverty line. The health law's subsidies go all the way to 400 percent of poverty, with smaller subsidies for families with higher incomes.
Thirty percent had incomes below the poverty line and could be eligible for Medicaid.
Women and children both made gains in access to affordable healthcare last year. Women and men were equally likely to struggle with medical bills in 2012, the CDC said. Women had previously been more likely to live in a family that had trouble paying for healthcare.
Nearly 22 percent of children younger than 17 lived in a family that had trouble paying for healthcare in 2012 — a drop of roughly 2 percent points from a year earlier.