What Is Medigap (Medicare Supplement) Insurance?

Understanding Medigap Insurance

Medigap, officially known as Medicare Supplement Insurance, is a type of private health insurance designed to supplement Original Medicare (Part A and Part B). Medigap policies help pay for some of the out-of-pocket costs that Original Medicare does not cover, including deductibles, copayments, coinsurance, and in some cases, medical care when traveling abroad.

Medigap plans are standardized by the federal government, meaning each plan type (identified by a letter) offers the same basic benefits regardless of which insurance company sells it. However, premiums can vary significantly between insurance companies for the same plan type.

Important: You cannot have a Medigap policy and a Medicare Advantage plan at the same time. Medigap works only with Original Medicare.

Available Medigap Plans

There are currently 8 standardized Medigap plan types available in most states: Plans A, B, D, G, K, L, M, and N. Plans C and F are available only to people who became eligible for Medicare before January 1, 2020.

Each plan offers a different level of coverage:

• Plan A: Basic benefits only — covers Part A coinsurance, Part B coinsurance, blood, and hospice care coinsurance
• Plan B: Basic benefits plus Part A deductible coverage
• Plan D: Plan B benefits plus skilled nursing facility coinsurance and foreign travel emergency coverage
• Plan G: The most comprehensive plan available to new enrollees — covers everything except the Part B deductible ($257/year in 2026)
• Plan K: Covers 50% of most cost-sharing, with an annual out-of-pocket limit
• Plan L: Covers 75% of most cost-sharing, with an annual out-of-pocket limit
• Plan M: Covers 50% of Part A deductible plus most other benefits
• Plan N: Covers most cost-sharing except Part B deductible and excess charges, with small copays for some visits

Note: Massachusetts, Minnesota, and Wisconsin have their own standardized Medigap plans that differ from the federal standard.

Medigap Costs and Pricing

Medigap premiums depend on the plan type, insurance company, your age, gender, location, and whether you use tobacco. There are three common pricing methods:

Community-rated (no-age-rated): Everyone pays the same premium regardless of age. This method provides more predictable costs over time.

Issue-age-rated: Premiums are based on your age when you first buy the policy. Younger buyers pay less, and the premium does not increase due to aging (though it may increase for other reasons like inflation).

Attained-age-rated: Premiums start lower but increase as you age. This is the most common pricing method. Policies may be cheaper initially but become more expensive over time.

As a general range, Medigap Plan G premiums typically run $100-$300+ per month depending on your state, age, gender, and insurer. Shopping around is essential since the same plan can vary by $100 or more per month between companies.

When to Buy Medigap Insurance

The best time to buy a Medigap policy is during your Medigap Open Enrollment Period, which is a one-time, 6-month window that begins the month you are both 65 or older AND enrolled in Medicare Part B.

During this window, you have guaranteed issue rights, meaning insurance companies must sell you any Medigap policy they offer at the best available price, regardless of your health status. They cannot charge you more or deny coverage due to pre-existing conditions.

After your Medigap Open Enrollment Period ends, insurance companies can use medical underwriting to decide whether to sell you a policy and how much to charge. You may be denied coverage or charged higher premiums based on your health history.

Some states offer additional protections, such as annual open enrollment periods or continuous guaranteed issue rights. Check your state's specific Medigap rules.

Medigap vs. Medicare Advantage

Choosing between Medigap and Medicare Advantage is one of the most fundamental Medicare decisions. Medigap works with Original Medicare to provide predictable, low out-of-pocket costs with the freedom to see any Medicare-accepting provider nationwide. The trade-off is higher monthly premiums and the need for a separate Part D plan.

Medicare Advantage bundles everything into one plan with lower premiums but requires using provider networks and may have higher out-of-pocket costs when you use services. MA plans often include extra benefits like dental, vision, and hearing that Medigap does not cover.

For people who want maximum provider flexibility and predictable costs, Medigap is often the better choice. For those who want lower premiums and value extra benefits, Medicare Advantage may be more appealing.