Original Medicare covers a lot, but it does not cover everything. There is no out-of-pocket maximum under Original Medicare, which means a serious illness or extended hospital stay can cost you tens of thousands of dollars in coinsurance and copays. Medigap — also called Medicare Supplement Insurance — fills those gaps by covering costs that Original Medicare leaves to you.

What Medigap Covers

Medigap policies are standardized by the federal government. That means a Plan G from one insurer covers exactly the same benefits as a Plan G from any other insurer — the only difference is the premium and the insurance company’s customer service. There are currently twelve standardized plan types, labeled A through N (with high-deductible variants for F and G).

The key gaps Medigap can cover include:

• Part A coinsurance for hospital stays (days 61-90: $408/day in 2024; lifetime reserve days: $816/day)
• Part B coinsurance (typically 20% of the Medicare-approved amount for outpatient care)
• Part A and B deductibles (depending on the plan)
• Skilled nursing facility (SNF) coinsurance (days 21-100: $204/day in 2024)
• Part B excess charges (what non-participating providers can charge above Medicare rates)
• Foreign travel emergency care (80% after a deductible, up to lifetime limits)

Use the comparison table below to see which gaps each plan covers.

Choosing the Right Plan

Plan G is the most comprehensive plan available to new Medicare enrollees (those eligible after January 1, 2020). It covers everything Plan F covered except the Part B deductible ($240 in 2024). Because premiums for Plan G are often significantly lower than Plan F was, many beneficiaries come out ahead with G.

Plan N offers slightly lower premiums than Plan G in exchange for copays of up to $20 for doctor visits and up to $50 for emergency room visits. It also does not cover Part B excess charges, so if you see providers who do not accept Medicare assignment, Plan G is safer.

High-deductible Plan G (G-HD) is a good option if you are healthy and want catastrophic coverage only. You pay the first $2,800 (2024) out of pocket before the plan kicks in — but after that, the plan covers everything Plan G covers. Premiums are much lower than standard Plan G.

Plans K and L have out-of-pocket limits and cover a percentage of most benefits rather than 100%. These are lower-premium options that still cap your annual exposure.

When to Buy Medigap

The best time to buy is during your Medigap Open Enrollment Period — the 6 months starting the month you are both 65 and enrolled in Part B. During this window, insurers cannot deny you coverage or charge you more based on pre-existing conditions. After this window closes, you generally need to pass medical underwriting to buy Medigap, which can result in denial or higher premiums depending on your health history.

Contact your State Health Insurance Assistance Program (SHIP) for free help comparing actual premium quotes in your area. Premiums vary substantially by insurer, state, and age — the standardized benefits table above shows what is covered, but not what it will cost in your ZIP code.

For help understanding when to enroll, visit our Medicare enrollment date calculator or explore our resources on IRMAA surcharges and income-based premiums.