What’s more, there are provisions in the law capping the financial burden the requirements will impose on the uninsured. If costs exceed 8 percent of their income, they are exempt from the individual mandate to buy insurance. And people can choose to pay a penalty instead of buying insurance. The fine would be $695, or 2.5 percent of a person’s income, whichever is greater.

Offering Subsidies

The law, enacted in March 2010, requires virtually all Americans to have insurance by 2014. It will expand coverage to the uninsured by offering them subsidies to buy policies on newly established health-insurance exchanges and making it easier for lower-income people to qualify for Medicaid, the federal- and state-funded insurance system for the poor.

Consumers’ expenses may climb because of a cost-cutting provision inserted in the law that will reduce federal aid to the uninsured if the subsidies exceed a certain threshold -- defined as 0.504 percent of the gross domestic product. The Congressional Budget Office says it expects that will happen.

In 2019, some families could see their premiums climb four times as quickly as the help they receive from the government, according to CBO. That means they will have to bear a larger share of the burden of purchasing coverage.

‘Major Challenge’

“That will be a major challenge,” said John McDonough, a public-health professor at the Harvard School of Public Health. “It makes the affordability picture far worse.”

The subsidies will be offered on a sliding scale, with those earning the least getting the most help. Those at the bottom of the income ladder, earning less than 138 percent of the poverty line -- about $33,000 for a family of four -- will get care through Medicaid. They will face minimal costs because the program has strict limits on co-pays -- if their states decide to opt in to the Medicaid expansion. The Supreme Court ruled in June that the government can’t compel states to do so, even as the justices upheld the law.

Those earning up to 400 percent of the poverty line -- about $92,000 for a family of four -- will receive tax subsidies to buy private insurance on a sliding scale.

‘Legitimate Concern’