What Is the Best Medicare Supplemental Insurance?

Medigap policies are standardized by letter (A through N, though Plan F closed to anyone newly eligible for Medicare on or after January 1, 2020). Plan G has become the most popular choice for new enrollees since Plan F closed, and it covers essentially all the gaps in Original Medicare's coverage, coinsurance, copays, and the Part A deductible, except the annual Part B deductible ($283 in 2026), after which it pays 100% of your share of Medicare-approved costs. Because it rides on top of Original Medicare, you can see any provider nationwide that accepts Medicare, with no referrals and no network restrictions, which matters a lot for retirees who travel or split time between states.

Medicare Advantage plans bundle Part A, Part B, and usually Part D drug coverage into a single private insurance plan, often adding extra benefits like limited dental, vision, or hearing coverage and sometimes a gym membership or other perks. The average national premium dropped to around $14 a month in 2026, and many plans are available at $0 premium beyond the standard Part B premium you still pay regardless of which path you choose. The tradeoff is a provider network, referral requirements in some plans, and cost-sharing through copays and coinsurance that accumulate up to an annual out-of-pocket maximum, roughly $9,350 in a typical 2026 plan, a real number in a serious illness year that Medigap users simply don't face.

The math changes depending on how much health care you actually use. In a healthy year, Medicare Advantage's low or zero premium clearly costs less than Medigap's $150-$260 combined monthly cost for Plan G plus a standalone Part D plan. In a year with a major surgery, hospitalization, or serious diagnosis, Medigap's predictable, near-total coverage often ends up costing less overall than Medicare Advantage's accumulated copays, coinsurance, and out-of-pocket maximum, plus Medigap avoids the uncertainty of whether your specialists and hospital are in-network.

Timing is the detail that catches people off guard. You get one guaranteed-issue window to buy a Medigap policy without medical underwriting: the six months starting the month you're both 65 or older and enrolled in Part B. During that window, an insurer cannot deny you coverage or charge more based on health conditions. Miss it, and buying or switching to Medigap later generally requires answering health questions, and insurers in most states can deny coverage or charge significantly more based on your health history. Moving from Medicare Advantage back to Medigap after that initial window, in particular, can be difficult if you've developed any chronic conditions in the meantime.

It's also worth being precise about what each path doesn't include. Medigap policies don't include drug coverage at all, so anyone choosing Medigap needs a separate standalone Part D plan, and both the Medigap premium and the Part D premium are subject to their own separate cost structures (and Part D carries its own IRMAA surcharge based on income). Medicare Advantage plans typically build drug coverage in, but check specifically whether a given plan does, since not all of them include it.

The decision that matters most isn't which plan is objectively "best," it's making a deliberate choice during your six-month Medigap guaranteed-issue window rather than defaulting into Medicare Advantage because it's the lower sticker price and revisiting the decision later when it's harder to change. If predictable costs and unrestricted provider access matter to you, that window is the one time the decision is entirely in your hands regardless of your health.

If you do choose Medicare Advantage, price out the plan's actual annual out-of-pocket maximum, not just its monthly premium, against a real scenario: a hospitalization, a specialist-heavy diagnosis, or a planned surgery. The premium difference between the two paths is the easy number to compare; the harder, more important one is what a bad health year actually costs under each.

• Choosing Medicare Advantage purely on the low or $0 premium without pricing what a serious illness year would actually cost against the plan's out-of-pocket maximum.
• Letting the one-time Medigap guaranteed-issue window pass without deciding, then finding out later that switching requires medical underwriting.
• Assuming Medigap includes drug coverage; it doesn't, and requires a separate standalone Part D plan.
• Assuming you can freely move between Medicare Advantage and Medigap every year the way you can switch Medicare Advantage plans during open enrollment; moving to Medigap specifically is not guaranteed-issue outside the initial window in most states.