The Bevin administration has estimated that the plan will result in 100,000 fewer Medicaid recipients after five years and save $2.4 billion, mostly in federal Medicaid funds. But Mr. Bevin couched the policy change as a moral rather than a fiscal decision, saying he did not care about the savings and saw it as an opportunity for Kentucky’s poor “not to be put into a dead-end entitlement trap but rather to be given a path forward and upward so they can do for themselves.”

Advocates for Medicaid beneficiaries said they disagreed with the Trump administration’s assertion, in approving Kentucky’s plan, that work requirements were consistent with the goals of Medicaid because work could improve people’s health.

“Considering that it will seriously harm over 100,000 Kentuckians, in violation of numerous provisions of Medicaid law, we are very seriously considering taking legal action — and as we analyze the meager legal rationale in the approval itself, it seems inevitable,” said Leonardo Cuello, director of health policy at the National Health Law Program, an advocacy group for the poor.

Emily Beauregard, the executive director of Kentucky Voices for Health, an advocacy group, said the state had provided little information about how it would make sure people were complying with work requirements, how exemptions would be determined and other details.

“We’re anticipating Kentuckians by and large are going to be extremely confused and worried about what they’re going to face and whether or not they’ll continue to have coverage,” Ms. Beauregard said. “They’ll be looking to advocates and enrollment assisters and their providers for answers, and at this point we don’t have any.”

She added, “The idea that we are encouraging work and independence, then taking away the health care that makes people more employable and better able to function — none of this adds up to something that’s going to be good for Kentuckians or our economy.”

But Hal Heiner, Kentucky’s Education and Workforce Development secretary, said during Mr. Bevin’s news conference that there was “an abundance of jobs” available to Medicaid recipients, as well as resources to prepare them.