Mayo Clinic is sending letters to hundreds of patients in certain Medicare Advantage plans urging them to find different health insurance if they want to keep getting care at the famed medical center in Rochester.

Mayo said the change, which will take effect in 2025, is driven by limited capacity for treating patients. It said fewer than 2,000 people will be affected nationally, including fewer than 600 in Minnesota.

In messages to the patients this week, Mayo said seniors with Medicare Advantage plans that lack network contracts can only schedule appointments for care next year if they obtain new coverage that includes the clinic as an in-network provider.

Patients can use original Medicare to receive care at Mayo, the notice said, although seniors could face significantly higher costs as a result. Open enrollment for Medicare starts Oct. 15.

"A substantial part of the care we provide every day will continue to be in service to patients who have Medicare," the clinic said in a statement to the Minnesota Star Tribune.

"Mayo Clinic in Rochester is out-of-network for some Medicare Advantage plans," thestatement said. "During open enrollment, we do encourage patients who would like to receive care at Mayo Clinic to verify access with their Medicare Advantage plan before enrolling for the upcoming year."

Exceptions will be granted on a case-by-case basis, officials said, for seniors with rare conditions where Mayo offers unique treatment expertise.

Several patients contacted the Minnesota Star Tribune this week to express frustration with the change.

Mark Giorgini, 68, of Mendota Heights said he has just begun exploring options but believes shifting to alternate coverage could be costly.

"I'm really disappointed by it," Giorgini said. "It will have a significant impact on me."

Mayo's move comes on the eve of a Medicare open enrollment season during which tens of thousands of Minnesota seniors will face disruptions as health systems go out-of-network with some Medicare Advantage plans.

There's no change in Mayo's network status with various plans but rather a shift in whether the clinic schedules appointments for established patients covered by "noncontract" Medicare Advantage plans.

Among Medicare Advantage plans operating in Minnesota, Blue Cross and Blue Shield, Humana, Medica, UCare and UnitedHealthcare all say that Mayo is in-network.

HealthPartners, Quartz and Sanford Health Plan say Mayo is out-of-network. Allina Health Aetna did not immediately respond to a request for comment.

Rather than provide a list of all Medicare Advantage plans where Mayo is in-network, the clinic gave patients the tax ID number for its operations in Rochester, so they can check with their insurers.

"Each plan even under the same insurer has nuances in coverage," the clinic said in a statement. "Thus, it's best for patients to check the specific plan they are interested in with our tax ID information to ensure the coverage will meet their needs."

Medicare Advantage is an increasingly popular program that allows seniors to choose to receive their government-sponsored benefits through a private managed care insurer.

The plans have grown because premiums can be low — $0 per month in some cases — and the coverage often comes with extra benefits, such as dental and vision coverage. Medicare Advantage plans also provide a maximum out-of-pocket limit on annual spending.

With original Medicare, by contrast, seniors can face hefty co-insurance payments,

Most people in original Medicare purchase a Medicare Supplement policy to cover the portion of care costs that original Medicare doesn't pick up. But these supplemental policies generally have higher premiums than Medicare Advantage plans, particularly if seniors also buy "standalone" Part D drug coverage. This drug coverage typically is bundled into lower-premium Medicare Advantage plans.

Medicare Supplements provide access to almost all doctors and hospitals across the country, whereas Medicare Advantage plans have networks that limit choices to varying degrees.

In 2022, the Mayo Clinic started enforcing a policy to not schedule appointments for seniors in non-contract Medicare Advantage plans. This enforcement applied to seniors who were new to Mayo.

At the time, Mayo cited capacity concerns as more patients with UnitedHealthcare Medicare Advantage coverage were using out-of-network benefits for scheduled care at the clinic. Later in 2022, Mayo and UnitedHealthcare reached an in-network agreement that remains in place.

The change at Mayo next year will apply to seniors who've received care at the clinic since before 2022. Mayo said demand for care from noncontract patients threatens to crowd out patients covered by insurers that have negotiated in-network contracts.

"No one that we sent a letter to is being cut off from Mayo Clinic care," a clinic official said in an interview. "They have the opportunity ... to go and look and find an option that fits and works."

Patients aren't so sure.

Giorgini of Mendota Heights has a Medicare Advantage plan from Connecticut-based Aetna that's heavily subsidized by his former employer. If he switches to another Medicare Advantage plan, he said, he will lose the subsidy.

Like all seniors, Giorgini could find coverage from original Medicare, but he worries he wouldn't be able to buy a Medicare Supplement policy. Health insurers that sell Medicare Supplements can deny coverage in Minnesota and most states to patients with pre-existing health conditions.

"If you're going to Mayo, you're essentially going to have a pre-existing condition and supplemental plans can turn you down," he said. "That means you're on original Medicare with the various holes that [Medicare Supplement] plans typically cover."

Geography could be another wrinkle. While Minnesota seniors can select among several Medicare Advantage plans where Mayo is in-network, it's not clear how much choice patients have in other states.

"Medicare Advantage plans are very complex and can be confusing," the clinic said in a statement. "We provided information to our patients on how they can work with their insurers and/or insurance representatives to select an option that works best for them and has Mayo Clinic in-network, if they would like to continue their care with us."