Most Medicare Advantage enrollees face Medigap denials if they switch

As Medicare's annual open enrollment season gets underway, millions of older adults are reviewing plan options, co-pays, and provider networks. Yet for those contemplating a return to traditional Medicare, a quiet regulatory hurdle looms large.

A new analysis from health policy research organization KFF reveals that nearly three-quarters—74 percent—of current Medicare Advantage enrollees have pre-existing health conditions that could lead private insurers to deny them a supplemental Medigap policy if they attempt to switch [KFF]. The finding highlights a critical, often misunderstood structural reality of Medicare: while joining a private Medicare Advantage plan is simple, returning to traditional fee-for-service Medicare with supplemental coverage can prove unexpectedly difficult once health issues arise.

The open enrollment crossroads

The annual Medicare open enrollment window opened on October 15 and runs through December 7 [Medicare Rights Center]. During this eight-week period, beneficiaries are permitted to move between Medicare Advantage and Original Medicare, pick a new standalone Part D drug plan, or change Advantage plans [Medicare Rights Center].

Many consumers view this seasonal window as a clean slate, assuming they can sample an all-in-one Medicare Advantage plan and return to traditional Medicare later if their medical needs become complex. However, while federal regulations guarantee the right to re-enroll in Medicare Part A and Part B, they do not guarantee access to an affordable Medigap policy [KFF].

Medigap policies, sold by commercial insurers, pay for out-of-pocket expenses that traditional Medicare leaves behind, such as Part A hospital deductibles and the standard 20 percent Part B coinsurance for doctor visits and outpatient therapies. Without Medigap or Medicaid, an individual in traditional Medicare faces unlimited out-of-pocket exposure [KFF].

The medical underwriting trap

Under federal law, beneficiaries receive a one-time, six-month "guaranteed issue" window for Medigap that begins the month they turn 65 and enroll in Part B [KFF]. During this brief period, insurers must sell any Medigap plan they offer at standard rates, regardless of medical history or existing illnesses [KFF].

Once that initial six-month window closes, federal protections largely vanish. Outside of narrow exceptions—such as moving out of a plan's service area or a plan terminating coverage—insurers in most states are legally permitted to use medical underwriting [KFF]. They can review an applicant's complete medical history, review prescription records, impose waiting periods for pre-existing illnesses, charge significantly higher monthly premiums, or deny an application outright [KFF].

Because Medicare Advantage enrollees tend to age into chronic medical conditions over time, KFF found that 74 percent possess medical diagnoses—ranging from heart disease and diabetes to cancer history—that typical Medigap underwriters use to reject applicants or inflate rates [KFF]. For these enrollees, leaving Medicare Advantage is not simply a matter of paperwork; doing so without Medigap could leave them exposed to serious financial risk.

A patchwork of state protections

Whether an enrollee faces this barrier depends heavily on geography. Because Medigap is regulated at the state level, a handful of states have implemented stronger consumer safeguards that exceed federal baseline rules [KFF].

A small number of states require continuous or periodic guaranteed issue, allowing beneficiaries to purchase a Medigap plan at specified times of year regardless of health status [KFF]. Others offer limited "birthday rules" that permit policyholders to switch between comparable Medigap plans around their birthdays, though these protections rarely extend automatically to someone trying to cross over from Medicare Advantage [KFF]. In the vast majority of states, traditional underwriting rules remain standard practice [KFF].

What enrollees should weigh this fall

Consumer advocates urge anyone weighing a switch to proceed with care before submitting enrollment changes [Medicare Rights Center].

Before dropping an existing Medicare Advantage plan in favor of Original Medicare, enrollees should contact Medigap insurers directly—or work through their local State Health Insurance Assistance Program (SHIP)—to verify whether they can clear medical underwriting in their state [Medicare Rights Center]. Submitting a Medigap application and receiving formal written approval prior to finalizing a plan cancellation can prevent an unexpected gap in supplemental coverage.

For those already enrolled in traditional Medicare with a working Medigap policy, consumer specialists issue a parallel caution: giving up a grandfathered Medigap plan to test out a Medicare Advantage plan carries long-term consequences [Medicare Rights Center]. Re-enrolling down the road may not be an option if health circumstances change [Medicare Rights Center].