Medicare Supplement (Medigap)

What it is

Medicare Supplement (also called Medigap) is private insurance that works alongside Original Medicare. Where Original Medicare covers most of the bill — but leaves you on the hook for deductibles, coinsurance (20% of Part B costs forever, no cap), and copays — a Medigap plan covers most or all of those gaps.

You keep Original Medicare. You see any doctor anywhere in the U.S. that accepts Medicare. The Medigap plan picks up where Medicare stops. You typically pay one premium for the Medigap plan and receive maximum coverage with minimal surprise costs.

The standardized plans

Here's something most people don't know: Medigap plans are federally standardized. A "Plan G" from BCBS covers the exact same things as a "Plan G" from Mutual of Omaha. The only difference is the price. That means shopping is easier than you'd expect — but there's still a real reason to use a broker who can pull every carrier's price for the same plan in your area.

• Plan G — most popular. Covers everything except the small Part B annual deductible (~$240). The closest you can get to "no surprises" coverage today. (Plan F was the most popular but is no longer available to people newly eligible for Medicare after Jan 1, 2020.)
• Plan N — slightly less coverage than G (small copays for office visits and ER, plus you may pay Part B excess charges if a provider doesn't accept assignment). In exchange, lower premium than G. Good fit if you're healthy and want to save monthly.
• High-Deductible Plan G — same coverage as Plan G but with a ~$2,800 annual deductible up front. Premium is much lower. Good fit if you have savings and want catastrophic-only coverage.
• Plans A, B, C, D, K, L, M — older plans, less commonly chosen today. Plan G has overtaken most of these.

The Open Enrollment window matters a LOT

You have a one-time, 6-month Medigap Open Enrollment Period that starts the month you turn 65 AND have Part B. During this window, you cannot be denied coverage or charged more for any health condition.

Outside this window, in most states, insurers can use medical underwriting — they can review your health history and either deny you, charge you more, or impose waiting periods for pre-existing conditions. (A few states like NY, CT, MA have year-round guaranteed issue or other protections; we'll check what applies where you live.)

Bottom line: if you're approaching 65, don't miss the Medigap Open Enrollment window. It's a one-time chance to lock in coverage with no health questions asked.

Who Medigap is a good fit for

• You want maximum doctor freedom — any provider that accepts Medicare
• You travel a lot or live in multiple states during the year
• You're willing to pay a higher monthly premium for predictable, near-zero out-of-pocket costs
• You'd rather know your healthcare cost up-front than face copays per visit
• You're enrolling during your Medigap Open Enrollment window (or a guaranteed-issue situation)

Important: you'll also need Part D separately

Medigap plans don't include prescription drug coverage. If you go the Medigap route, you'll add a standalone Part D plan for prescriptions. Total monthly cost for a typical 65-year-old in Texas with Plan G + Part D: usually $150-$250/month combined.

→ See how Medicare Advantage compares · → Part D guide · → Back to Medicare 101