Medicare Medigap rules explain who can buy supplemental coverage

The 6-month Medigap enrollment window is where your rights are strongest. Before you compare prices, you need to know whether you qualify at all, because federal rules, state law, and your current Medicare coverage can change the answer quickly.

Who can buy a Medigap policy

In general, you need Original Medicare, meaning Part A and Part B, before you can buy Medigap. A Medigap policy covers only one person, so a spouse does not share your policy and must buy a separate one if they want the same kind of supplemental coverage.

Medigap is designed to pay some of the out-of-pocket costs that Original Medicare does not cover. It helps with items such as coinsurance and deductibles, but it works only after Medicare has paid its share. If you are enrolled in Medicare Advantage instead of Original Medicare, you are usually not in the Medigap market at all.

Wisconsin’s Board on Aging and Long Term Care states that insurers cannot sell a Medicare Supplement policy to a beneficiary enrolled in Medicare Advantage.

The 6-month window that gives you the strongest rights

Under federal law, your Medigap Open Enrollment Period lasts 6 months and begins the first month you have Medicare Part B and are 65 or older. During that window, insurers cannot refuse to sell you a policy or deny you coverage because of pre-existing health problems.

During that 6-month period, you can enroll in any Medigap policy an insurance company sells. In most cases, you do not have a federal right to switch Medigap policies unless you are still within open enrollment or you qualify for a guaranteed issue right.

Guaranteed issue rights are the main exception when you have missed the ordinary buying window or lost other coverage protections. The 2021 Medicare guide applies the federal guaranteed issue rules in that section to Medigap and Medicare SELECT policies. A qualifying event can preserve access even when a normal application would otherwise face medical underwriting.

Why state law can change the answer

Medicare’s buy-timing guidance applies only to federal rights. States can offer more opportunities under state law. Many states provide additional protections or purchase windows beyond what federal law requires.

Eligibility rules for people under 65 vary by state, and some states offer Medigap plans to people under 65 who have qualifying circumstances. That means a person who qualifies for Medicare before age 65 may face a different supplement market depending on where they live.

If you are under 65 or may have a state-level protection that goes beyond the national minimum, contact your state to find out whether state law offers more chances to buy a Medigap policy.

How Medigap changes your cost-sharing

Medigap does not replace Medicare. It sits on top of Original Medicare and helps pay the Medicare-approved amount for covered health care costs after Medicare pays its portion.

The policy generally pays coinsurance only after the deductible has been met unless the policy also covers the deductible. If a policy does not include deductible coverage, you still need to satisfy that deductible before the supplement starts picking up coinsurance on the covered service.

In most states, only a few standardized Medigap plans are available, although many insurance companies may sell the same standardized plan. The plan names may look similar from one insurer to another because the benefit design is standardized, even when the company selling it is different.

A practical way to check your eligibility before you shop

Start with your current Medicare status. If you have Original Medicare, you are in the correct starting place for Medigap. If you are enrolled in Medicare Advantage, the supplement path is usually closed unless you first move back to Original Medicare and fit another qualifying rule.

Next, check your timing. If you are 65 or older and the first month you had Part B is still inside your 6-month Medigap Open Enrollment Period, you are in the strongest position to choose among available policies. If that window has passed, the next question is whether you have a guaranteed issue right or a state rule that expands your options.

Then look at your state. States may offer more opportunities under state law, and under-65 eligibility can vary widely. The same Medicare card can lead to very different supplement choices depending on whether local rules add protections or simply follow the federal floor.

Finally, compare plans with the cost-sharing rules in mind. Check whether the policy covers the deductible, how soon it starts paying coinsurance, and which standardized plan designs are sold in your state.