SAN FRANCISCO — For most newly unemployed workers, maintaining family health coverage through an extension of workplace benefits is a prohibitively expensive proposition, a recent study suggests.

With unemployment hitting a 16-year high in December, measures such as federal subsidies to help jobless people afford coverage are all the more urgent, argues Families USA, a national advocacy organization for health care consumers in Washington.

COBRA is the acronym for a federal law enacted in 1986 that allows many laid-off workers and their dependents to remain on an employer’s group health plan for 18 months as long as they pay the full cost of coverage and a 2-percent administrative fee. The law was designed to keep people from falling into the ranks of the uninsured when they lose a job — especially if they have a preexisting condition that would make it hard to secure coverage on the individual market.

But after a rapid rise in health care costs this decade, the economics of continuing on COBRA are beyond the reach of many, according to a study released this month by Families USA. The average monthly COBRA premium for family coverage, $1,069, consumes 84 percent of the average monthly unemployment check, which is $1,287, the study found.

“If you’re subsisting on an unemployment insurance check and 84 percent of that check is what’s needed to continue family coverage, clearly it’s unrealistic to expect you can afford to do that and still have money left for food and rent and utilities and other necessities,” said Ron Pollack, executive director of Families USA.

The mismatch is worrisome after the Labor Department reported earlier this month that the U.S. unemployment rate leaped to 7.2 percent in December, its highest level since January 1993. Employers shed a total of 2.6-million jobs last year, with the bulk of the losses coming in the last four months of the year. More than 11-million people are without work.

“We haven’t had this kind of pressure of more and more people being laid off and the prospects of that getting worse since COBRA was established,” Pollack said.

For single coverage, an individual would have to allocate 30 percent of his or her unemployment check to continue on COBRA. The national average cost of employer-provided coverage for an individual plus the 2-percent fee comes to $4,656 a year, or $388 a month. For family coverage, the cost jumps to $12,823 a year.

Research has shown that for every one percentage point rise in the unemployment rate, the number of uninsured Americans rises by about 1.1 percent.

Pollack advised married workers who lose their jobs and the health insurance that goes with them first to see if they can get coverage through their spouse’s employer. But they have to act quickly, typically within a month or two.

The same rule applies for checking out your options under COBRA. Don’t delay or else you may lose eligibility, he said. “Most people don’t understand this is time-limited.”

For people with children, it pays to determine whether the kids may qualify for the state children’s health insurance program or Medicaid, Pollack said.