Most Medicare Advantage Enrollees Risk Medigap Denial

74% of Medicare Advantage Enrollees Have a Condition That Could Block a Medigap Switch

A new analysis from KFF, a nonpartisan health policy research organization, found that 74% of Medicare Advantage enrollees, or about 20.9 million people as of 2023, had at least one pre-existing medical condition that insurers could use to deny a Medigap policy outside a one-time federal protection window. The analysis, published October 13, 2026, reviewed real Medigap insurer applications to identify which health conditions are commonly used to screen out applicants. Read the full KFF analysis here.

Medicare Advantage is a private insurance alternative to traditional Medicare that often includes extra benefits and lower premiums but typically limits care to a network of providers. Medigap, also called Medicare Supplement insurance, is a separate private policy that pays some of the out-of-pocket costs traditional Medicare does not cover, such as copays and deductibles. Medigap insurers in most states can use medical underwriting, meaning they can review an applicant's health history and charge more, add a waiting period, or deny coverage based on it.

Federal law gives Medicare Advantage enrollees one guaranteed window to switch back to traditional Medicare and buy a Medigap policy without medical underwriting: a 12-month trial right available to people who joined Medicare Advantage when they first became eligible for Medicare. Outside that window, in most states, a Medigap insurer can ask health questions and reject an applicant for conditions on its underwriting list.

Risk Rises With Age and Varies Sharply by State

According to KFF's review, the share of Medicare Advantage enrollees with a condition that could trigger a Medigap denial increases with age, reflecting the higher prevalence of chronic conditions among older enrollees. KFF also found that the risk of denial varies by state because Medigap consumer protections are set largely at the state level rather than federally.

A small number of states, including New York, Connecticut, Massachusetts, Maine, and Minnesota, require Medigap insurers to sell policies to most applicants on a guaranteed issue basis regardless of health status or timing. In the remaining states, an enrollee who wants to leave Medicare Advantage after their trial period ends can be medically underwritten, and KFF's review of Medigap applications identified conditions such as diabetes, heart disease, and a history of cancer among those commonly flagged.

What This Means for Your Medicare Decision

This KFF analysis does not allege wrongdoing by any insurer. It describes how existing underwriting rules interact with common health conditions once an enrollee tries to leave Medicare Advantage outside the trial period. The practical risk for readers is a lock-in effect: a health condition diagnosed after enrolling in Medicare Advantage can make it harder, or impossible in some states, to later buy a Medigap policy at standard rates.

A few steps can reduce this risk for current and future enrollees:

• Check whether your state requires guaranteed issue Medigap coverage outside the federal trial period. State insurance department websites list these protections.
• If you are new to Medicare, know that your 12-month trial right to switch from Medicare Advantage to traditional Medicare plus Medigap, without medical underwriting, starts the day your Medicare Advantage coverage begins.
• Compare plan networks, drug formularies, and total expected costs before choosing Medicare Advantage, since a later underwriting denial could leave you with the same plan type for the rest of your Medicare years.
• During Medicare's Annual Election Period, which runs October 15 through December 7 each year, or the Medicare Advantage Open Enrollment Period from January 1 through March 31, review whether your current plan still fits your health needs before it potentially becomes harder to change course.
• Speak with a licensed insurance agent or your State Health Insurance Assistance Program (SHIP) counselor before switching plan types, especially if you have an ongoing health condition.

KFF's findings underscore that the choice between Medicare Advantage and traditional Medicare with Medigap is not easily reversible for most people in most states. Readers nearing Medicare eligibility, or currently enrolled in Medicare Advantage and considering a switch, should treat this as a decision to revisit with full information rather than a routine annual adjustment.