Medicare Supplements
Learn how standardized Medigap plans work with Original Medicare to cover certain cost sharing.
What a supplement does
Medicare Supplement Insurance, or Medigap, is a private policy that may pay some of the deductibles, copays and coinsurance left by Original Medicare Parts A and B. Original Medicare generally pays first for a Medicare-covered service and the Medigap policy pays its standardized share second. Medigap does not replace Original Medicare and cannot be used to pay Medicare Advantage plan cost sharing.
Official source: Medicare: How Medigap works ↗ · Medicare: Original versus Advantage ↗
Choose a letter before a carrier
In most states, Medigap plans are standardized by letters A–D, F, G and K–N. The same letter has the same basic benefits regardless of company, while premium, discounts, service and availability can differ. Massachusetts, Minnesota and Wisconsin use different standardization. Use Medicare’s benefit chart to compare letters, then compare the same letter among local carriers.
Official source: Medicare: Medigap plan benefits ↗ · Medicare & You 2027, Medigap section (2026 chart) ↗
Drug and travel gaps
Newly sold Medigap policies do not include Part D drug coverage; consider a standalone drug plan if you need covered prescriptions. Some Medigap letters include limited foreign-travel emergency coverage, but no Medigap policy is general travel insurance. Routine dental, vision, hearing aids and long-term custodial care are generally outside standard Medigap benefits. Check each need separately.
Official source: Medicare: How Medigap works ↗ · Medicare: Medigap coverage ↗ · Medicare & You 2027, Medigap section (2026 chart) ↗
Timing can control whether you can buy
Federal Medigap Open Enrollment lasts six months starting the first month you are at least 65 and enrolled in Part B. During it, an insurer generally cannot reject you for health history or charge more because of it. Outside that window, underwriting may apply unless a specific guaranteed-issue or state right exists. It is not renewed every fall.
Official source: Medicare: Buying Medigap ↗
Calculate the whole household cost
A Medigap policy covers one person and has a monthly premium in addition to Part B. A spouse needs a separate policy. Compare monthly premium, Medicare cost sharing left under the letter and any separate Part D costs. Ask whether discounts apply, how the carrier rates the policy and whether premiums can rise with age or other factors.
Official source: Medicare & You 2027, Medigap section (2026 chart) ↗ · Medicare: Medigap costs ↗