Health insurance for up to 15 million Americans is hanging in the balance.
This, as a pandemic-era protection that allowed people to stay on Medicaid for three years without reapplying, is now expired.
"States will start looking at their Medicaid rosters and re-determining whether or not people should still stay covered. Millions of people are likely to lose coverage, even though they might still be eligible," said Dr. Avenel Joseph, VP of policy for Robert Wood Johnson Foundation.
"It would be just a nightmare," said Medicaid recipient Jeffrey Jackson.
Recipients like 62-year-old Jackson in Arkansas who rely on the program for health care could fall through the cracks.
"I would have to make whether I would eat or whether I would get my medication," Jackson said.
Residents in Arizona, Arkansas, Idaho, New Hampshire and South Dakota will be the first to bear the brunt of the terminations.
The five states will start cutting off coverage in April, followed by 14 more states in May and 20 additional states plus the District of Columbia in June. All states must complete their redeterminations over the next 14 months.
"This is the largest reshuffling of people in insurance programs since the passage and implementation of the Affordable Care Act more than 10 years ago," Dr. Joseph said.
The Department of Health and Human Services is warning children, young adults, and Black and Latino Americans may be disproportionately impacted.
"I still haven't heard anything," said Lily Quintanilla.
A Texas mom of four, Quintanilla said her 6-year-old was born with cerebral palsy.
"With Medicaid, we're able to sustain him. I guess, you can say, without it, I don't think we would have him here today," Quintanilla said.
Medicaid enrollment has ballooned since March 2020, when lawmakers passed the Families First Coronavirus Response Act, which prevented states from involuntarily removing anyone from coverage. In exchange, Congress boosted states' federal Medicaid match rates by 6.2 percentage points.
The provision was initially tied to the national public health emergency, but lawmakers changed that as part of the federal spending bill that passed in December. In addition to being able to start conducting terminations in April, states will receive an enhanced federal match through the rest of this year, though it will phase down over time.
More than 92 million Americans were enrolled in Medicaid and the Children's Health Insurance Program in December, up 31% since February 2020, according to the most recent data available from the Centers for Medicare and Medicaid Services.
Reviewing the eligibility of all those enrollees will be a monumental task for state Medicaid agencies, many of which are also contending with slim staffing. To gear up, they are hiring new employees, temporary workers or contractors or bringing back retirees, according to a recent survey conducted by Georgetown and the Kaiser Family Foundation.
Most states can automatically renew coverage for at least some of their enrollees using other data, such as state wage information. But agencies must get in touch with others in their Medicaid programs, which proved challenging even prior to the pandemic. Most states are using multiple methods to update enrollees' contact information, including working with insurers that provide Medicaid coverage to residents.
If notices sent by mail are returned, states must make good faith attempts to contact enrollees through at least two other methods before cutting them off. And states have to adhere to additional requirements to continue to qualify for the enhanced match. If they don't, CMS also could suspend their terminations, require they take corrective action or impose monetary penalties.
Of the roughly 15 million people who could lose Medicaid coverage, about 8.2 million will no longer qualify, according to a Department of Health and Human Services analysis released in August. Some 2.7 million of these folks would qualify for enhanced federal subsidies for Affordable Care Act policies that could bring their monthly premiums to as low as $0.
Some 6.8 million people, however, will be disenrolled even though they remain eligible.
Though the federal government has given states more than a year to conduct the eligibility reviews and terminations, some plan to move much more quickly.
Idaho, which has been monitoring enrollees' eligibility throughout the pandemic, plans to complete its reevaluations by September, which it touts as one of the fastest timelines in the country.
Of the nearly 450,000 Idahoans in the program, about 150,000 of them either don't qualify or haven't been in touch with the state in the past three years. The state began sending notices in February to those who face termination. People have 60 days to respond before they are removed.
Those that are not eligible have 60 days from their termination date to enroll in Idaho's state-based Obamacare exchange, Your Health Idaho. The exchange receives information nightly from the state Medicaid agency about residents who no longer qualify for public coverage but may be eligible for federal subsidies for Affordable Care Act policies.
The exchange is reaching out to those folks weekly while they still have Medicaid and then every 15 days during the two-month special enrollment period via various methods, including mail, email and text messages, said Pat Kelly, Your Health Idaho's executive director.
The exchange works with 900 agents, brokers and enrollment counselors who can help folks sign up for policies. And it plans to start an advertising campaign this month highlighting the hefty subsidies.
"We have to really help Idahoans know and understand that low-cost options are available, and most importantly, that it's comprehensive health insurance that they can get for $0 a month," Kelly said.
Still, advocates in Idaho are concerned that the state's push to unwind quickly will result in eligible residents losing coverage.
Many people are not aware that they once again need to prove that they qualify, and the state agency is understaffed and underfunded, said Hillarie Hagen, health policy associate at Idaho Voices for Children. Renewal letters may not make it to enrollees, and those who need help may not be able to get through to customer service.
"We are very concerned about families, and particularly children, losing health coverage without their knowledge -- that they will find out when they show up to the doctor," Hagen said.
Aware that many people don't know they'll have to renew their eligibility, Arizona's Medicaid agency last summer sent text messages and letters and made robocalls to enrollees, asking them to update their contact information. It is also working with community partners, health care providers, pharmacies and insurers. And it's ramping up another text campaign since the prior one was so successful, said Heidi Capriotti, public information officer for the Arizona Health Care Cost Containment System.
While the state can automatically redetermine the eligibility of about 75% of its Medicaid participants, it still has to connect with about 670,000 residents who could lose coverage because they are no longer eligible or they haven't responded to the agency's requests. The state plans to take 12 months to assess whether its enrollees still qualify.
South Dakota will start terminating Medicaid enrollees in April, though some low-income adults may become eligible again in July, when the state's Medicaid expansion program begins.
Voters approved the broadening of Medicaid to low-income adults at the ballot box in November, over the objections of the Republican governor and legislature.
Nearly 152,000 residents were enrolled in Medicaid in January, an increase of more than 30% from March 2020, according to the state's Department of Social Services. But more than 22,000 people appear to be ineligible currently.
The agency said in an FAQ that it will prioritize reviewing folks who are most likely to be ineligible because they no longer meet a coverage group or their income has increased, among other reasons.
Those who are not eligible will be disenrolled with 10-days' notice. If they appear eligible for expansion in July, they'll receive a notice about it when they are terminated and sent a reminder in June. The agency is encouraging any enrollees who are determined to be ineligible to reapply after Medicaid expansion takes effect.
But that three-month gap can wreak havoc on low-income residents' health, said Jen Dreiske, deputy director of South Dakota Voices for Peace, which is working with the state's immigrants and refugees to inform them of the unwinding. These folks may have to go without their heart medication or their cancer treatment. They may also be afraid to go to the doctor because of the cost.
"Why can't we just wait until July 1?" Dreiske said. "Our concern is that people are going to get sick or die because they're not going to be able to access the health care that they so desperately need."
One reason Americans eligible for Medicaid might lose coverage is they missed a letter in the mail, so get in touch with your state provider. And if it turns out you no longer qualify, you can look for insurance through the Affordable Care Act.
ABC News and CNN contributed to this post.