The Biden administration this week accelerated efforts to fund opioid addiction treatment in jails and prisons, a core part of its drug policy agenda, calling on states to adopt a novel Medicaid program that will cover health care for incarcerated people.

Under new guidance from the Centers for Medicare and Medicaid Services, states can ask the federal government to allow Medicaid to cover addiction treatment for up to 90 days ahead of someone’s release. Public health experts say that providing treatment during that critical period could help people survive the often harsh conditions of jails and prisons, then more easily transition back to the community.

Correctional facilities, where inmates disproportionately have opioid use disorder and often cannot find treatment during and after their incarceration, have claimed a spot on the forefront of the nation’s devastating overdose epidemic, which now kills more than 100,000 Americans each year.

“That’s where most people are, and that’s where you’re going to get the most benefit,” said Dr. Rahul Gupta, the director of the White House’s Office of National Drug Control Policy, referring to the high concentration of incarcerated Americans with opioid use disorder. Neglecting to treat addiction in jails and prisons, he added, comes at the “highest cost to society, to taxpayers.”

The stakes of the issue are neatly represented by a row of white bars looming over a common area of the Curran-Fromhold Correctional Facility, a jail in Philadelphia along the Delaware River that Dr. Gupta visited on Thursday. The bars, which line a second-story walkway, are meant in part to prevent residents with opioid use disorder from jumping to attempt suicide while they have withdrawal symptoms, according to officials at the facility.

Federal law prohibits incarcerated Americans from receiving coverage through Medicaid, the federal-state health insurance program for low-income people, unless in an inpatient setting such as a hospital. The prohibition, known as the inmate exclusion policy, means that states, counties and cities typically foot the bill for programs that help opioid users manage or prevent the debilitating cravings and withdrawal symptoms that follow them through incarceration.

Curran-Fromhold’s medication treatment program offers methadone and buprenorphine, the two most common, effective opioid addiction treatments, which have been shown to ease cravings. It is funded by the City of Philadelphia, making it an obvious target for Medicaid coverage, Dr. Gupta said. Medication programs in jails and prisons can be expensive to operate.

Bruce Herdman, the chief of medical operations for Philadelphia’s jail system, said that if Pennsylvania were to secure Medicaid funds for the jail, the move would allow the system to save money for other key programs and medications.

“They will allow us to provide services that we at present can’t afford,” he said, referring to the possible Medicaid funds.

Even before issuing the new guidance, the Biden administration had encouraged states to apply for the Medicaid program. In January, California became the first state to be approved for it, and more than a dozen other states have applications pending. Dr. Gupta said the new guidance would most likely compel more states to ask for Medicaid coverage for the kind of help that Curran-Fromhold offers.

One state that could seek funds is Pennsylvania, which has contended with a devastating rise in drug overdoses in recent years. A spokesman for the Pennsylvania Department of Human Services said that state officials were still evaluating plans to apply for the Medicaid program and were focused in the meantime on reinstating the Medicaid benefits of inmates after they are released.

Regina LaBelle, who served as the acting director of the Office of National Drug Control Policy under President Biden, said she worried that state health departments might not have the resources to apply for the program.

“It takes a lot of staff time,” she said. “Do they have people in their Medicare and Medicaid services office who can put time and energy into that document?”

Some conservative critics of opioid addiction treatment say that because buprenorphine and methadone are opioids, their use should not be encouraged. But the Medicaid program already has shown bipartisan appeal, with some conservative-leaning states, such as Kentucky, Montana and Utah, applying for it.

For states that want to participate in the program, the federal government is calling for correctional facilities to offer methadone and buprenorphine. The guidance also asks states to suspend, rather than terminate, Medicaid coverage while people with the insurance are incarcerated, allowing them to more quickly transition back into their health plans once they are released.

Dr. Gupta said that such an approach could better allow those who are newly released to see a doctor they had seen before their incarceration. Correctional facilities will also be expected to provide inmates with a 30-day supply of treatment upon their release, giving people a head start as they re-enter society.

“It’s all of the transitions where things fall apart, both from the transition from outside to inside, then inside to outside,” said Dr. Josiah D. Rich, an epidemiologist at Brown University.

People in jails and prisons are especially vulnerable to fatal overdoses shortly after they are released, when their tolerance for drugs has weakened. Studies show that the risks of overdosing in the days and weeks after release are reduced substantially if an incarcerated person uses either buprenorphine or methadone.

About two million people are held in jails and prisons on any given day in the United States, and a substantial portion of them have opioid use disorder, federal officials say. Withdrawal symptoms can be especially acute during shorter stays in jails, many of which do not have treatment programs. Around nine million people cycle through jails every year, the federal government estimates.

Buprenorphine and methadone typically require sustained, uninterrupted use to help drug users gradually dull cravings. The average length of a stay in a Philadelphia jail is around 120 days, meaning that the Medicaid program, with its 90-day coverage period, could pay for treatment for most or all of a person’s time there.

Researchers from the Jail and Prison Opioid Project, a group that Dr. Rich helps lead that studies treatment among incarcerated people, estimate that only about 630 of the nation’s roughly 5,000 correctional facilities offer medication treatment for opioid use disorder. About 2 percent of incarcerated people in the United States are known to have received such treatment while in jail or prison, the researchers estimate.

Dr. Gupta pointed to what he said was a glaring irony in a large segment of the American prison population: People are incarcerated for their drug use, then denied treatment for it.

The Biden administration’s push for states to use Medicaid funds in jails and prisons is overlapping with a bipartisan effort in the House and Senate to pass the Medicaid Re-entry Act, which would grant coverage in the 30 days before an inmate’s release.

The administration has said that by the summer, all 122 Federal Bureau of Prisons facilities will be equipped to offer medication treatment. But most incarcerated people are in state and local prisons and jails, which feature a patchwork of medication policies that can vary by site. Some correctional facilities allow only one treatment, while others allow medication only for those who were receiving it before they were incarcerated.

“There is stigma both around using medications for treatment but also stigma around opioid use disorder in general,” said Dr. Elizabeth Salisbury-Afshar, an addiction physician at the University of Wisconsin-Madison who has advised jails on treatment programs. “There is a broader educational gap.”

Dr. Dorian Jacobs, a physician who helps run the Curran-Fromhold jail’s addiction treatment program, said she had encountered residents with opioid use disorder who did not realize it is a disease that should be treated like any other.

“It’s just a part of who we are,” she said.