74% of Medicare Advantage Enrollees Could Be Denied a Medigap Policy, KFF Finds: What to Know Before You Switch

Medicare’s open enrollment period, which runs through Dec. 7, is when many people weigh leaving a Medicare Advantage plan for traditional Medicare. A new analysis suggests most of them could have trouble buying the supplemental coverage that usually goes with it.

Nearly three-quarters of Medicare Advantage enrollees, 74%, or about 20.9 million people, had at least one pre-existing condition in 2023 that could lead an insurer to deny them a Medigap policy, according to a KFF analysis of Medicare Advantage data. Florida had the highest share in the country, at 82%.

The analysis matters for anyone thinking about switching, because outside of a few protected windows, federal law lets Medigap insurers turn applicants down, or charge them more, based on their health history.

What is Medigap, and why does it matter if you switch?

Medigap, also called Medicare supplement insurance, is sold by private companies and helps pay the deductibles, copayments and coinsurance that traditional Medicare leaves to the patient. Traditional Medicare has no cap on out-of-pocket spending, KFF notes, so many enrollees rely on Medigap, employer retiree coverage or Medicaid to fill the gaps.

Medigap premiums averaged $244 a month in 2025 among current policyholders, according to KFF. In 2024, 12.9 million people, or 46% of traditional Medicare beneficiaries, had a Medigap policy. Medigap does not work with Medicare Advantage plans.

What did KFF find?

KFF compared diagnoses in Medicare Advantage encounter data with the health questions on Medigap applications from the six largest Medigap insurers. Among its findings:

• At least 1 in 5 Medicare Advantage enrollees had peripheral vascular disease (25%), chronic kidney disease (24%), coronary artery disease (21%) or diabetes with related complications (21%), all conditions that could trigger a denial.
• Other conditions that can lead to a denial include Alzheimer’s disease and dementia, atrial fibrillation, COPD, heart failure, Parkinson’s disease, stroke and some cancers.
• The share rises with age, reaching 88% of enrollees 85 and older.
• Among enrollees under 65, who qualify for Medicare because of a disability, 77% had a potentially deniable condition.
• By state, the share ranged from 82% in Florida and 78% in Louisiana to 59% in Alaska.

The true share may be higher, KFF said, because applications also ask about recent hospital stays, home health care, nursing home care and tests or surgery a doctor has recommended. KFF also noted that Medicare Advantage plans have a financial incentive to record diagnoses, which may make more enrollees look ineligible than would be the case in traditional Medicare.

When can insurers not turn you down?

Federal law guarantees access to a Medigap policy, regardless of health, in a handful of situations, according to KFF’s review of federal and state rules:

• The one-time, six-month Medigap open enrollment period that starts when someone 65 or older first enrolls in Medicare Part B.
• A trial period for people who join a Medicare Advantage plan when they first become eligible for Medicare and leave it within the first year. People who dropped a Medigap policy to try Medicare Advantage for the first time can also return to their policy within a year.
• When a Medicare Advantage plan ends coverage in the enrollee’s area. More than 4 million people will see their Medicare Advantage or stand-alone drug plan end on Dec. 31, as HNC reported.
• When an employer ends retiree coverage, or when a Medigap insurer goes bankrupt or commits fraud.

People with those qualifying events generally have 63 days to apply. Outside those windows, an insurer may deny a policy, charge more or apply a waiting period for a pre-existing condition.

Do some states offer more protection?

Yes. Connecticut, Massachusetts, Maine and New York require insurers to sell Medigap to people 65 and older at any time or once a year, regardless of health, KFF found. Delaware, Illinois, Minnesota and Rhode Island have narrower expanded protections. Thirty-seven states add guaranteed issue for certain events, such as a change in retiree coverage, and 38 states require insurers to offer at least one Medigap policy to people under 65 with disabilities.

What should seniors and caregivers do before switching plans?

• Check whether you are in a guaranteed issue window before you leave a Medicare Advantage plan. If you are not, ask insurers in your state whether you would be accepted before you switch.
• Read the health questions on the Medigap application. Many say that answering “yes” to any question makes you ineligible.
• If your plan is ending Dec. 31, keep the termination notice; it is your proof of a guaranteed issue right.
• Get free, unbiased help from your State Health Insurance Assistance Program (SHIP), or call 1-800-MEDICARE.
• Use HNC’s open enrollment checklist to compare drug coverage and costs before Dec. 7.

Key Takeaways

• 74% of Medicare Advantage enrollees, about 20.9 million people, had a condition in 2023 that could lead to a Medigap denial, KFF found.
• Florida had the highest share at 82%; Alaska had the lowest at 59%.
• Outside guaranteed issue windows, federal law lets Medigap insurers deny coverage or charge more based on health history.
• Four states (CT, MA, ME, NY) let people 65 and older buy Medigap regardless of health at any time or once a year.
• Medicare open enrollment ends Dec. 7, 2026.

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Featured image: A physician talks with an older patient and a family member. Illustrative photo. (Photo by Rhoda Baer, National Cancer Institute, public domain, via Wikimedia Commons)