“My husband didn’t choose to be born this way,” Ms. Bruce said. The union representing her, a chapter of the Service Employees International Union, has objected to the changes. Her employer, Providence Health & Services, says it designed the plans to avoid having employees shoulder too much in medical bills and has reduced how much workers pay in premiums.

Proponents of the law say the Cadillac tax is helping bring down costs by making employers pay attention to what their health care costs are likely to be in the long run. “It’s really one of the most significant provisions” in the Affordable Care Act, said Jonathan Gruber, the M.I.T. economist who played an influential role in shaping the law. “It’s focusing employers on cost control, not slashing,” he said.

Cynthia Weidner, an executive at the benefits consultant HighRoads, agreed that the tax appeared to be having the intended effect. “The premise it’s built upon is happening,” she said, adding, “the consumer should continue to expect that their plan is going to be more expensive, and they will have less benefits. ”

The trend is accelerating. The percentage of employers revising their plans as a result of the tax has increased to 17 percent this year from 11 percent in 2011, according to a survey of United States companies released this month by the International Foundation of Employee Benefit Plans.

Although the tax does not start until 2018, employers say they have to start now to meet the deadline and they are doing whatever they can to bring down the cost of their plans. Under the law, an employer or health insurer offering a plan that costs more than $10,200 for an individual and $27,500 for a family would typically pay a 40 percent excise tax on the amount exceeding the threshold.

“I’m actually much more focused on the Cadillac tax in 2018 than on 2014,” Steve First, a benefits executive at Pfizer, said at a recent meeting of employers. “For us, 2018 is a challenge.”

Raising deductibles is one way to lower the cost.

Since 2009, the percentage of workers in plans with a deductible of at least $2,000 has doubled, to 14 percent, by 2012, according to the Kaiser Family Foundation. A little over a third of workers are in plans with a deductible of at least $1,000 a year.