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Does Medigap cover the 20 percent Medicare does not pay?

Yes, and depending on the plan letter it covers several other gaps too. Here is exactly what each one pays.

Updated August 17, 2026 · 2 min read

Yes. Covering the Part B coinsurance, the 20 percent Medicare leaves you, is the core function of every Medigap plan. Every standardized plan letter includes it.

The gaps a supplement can fill

• Part B coinsurance, the 20 percent. Covered by every plan.
• Part A hospital coinsurance, plus an extra 365 days of hospital coverage after Medicare's benefits are used up. Covered by every plan.
• The Part A hospital deductible, which applies per benefit period rather than annually. Covered by most plans.
• Skilled nursing facility coinsurance, which begins after the first stretch of days.
• The first three pints of blood.
• Hospice coinsurance.
• Part B excess charges, which is what a non participating provider can bill above Medicare's approved amount.
• Foreign travel emergency care, usually up to a lifetime limit.

Which of these your policy covers depends on the plan letter you choose.

The extra 365 hospital days

This one gets overlooked and it is significant. Medicare's inpatient hospital coverage runs out after a set number of days across a benefit period plus lifetime reserve days. Every Medigap plan adds 365 additional days of hospital coverage after Medicare's are exhausted.

For a catastrophic hospitalization that is the difference between a manageable situation and a financial one.

What is not covered

The Part B annual deductible is no longer covered by plans sold to people newly eligible for Medicare on or after January 1, 2020. Plans C and F, which covered it, are closed to newly eligible beneficiaries.

If you became eligible before that date and already have Plan C or F, you keep it. See Plan F versus Plan G.

How this feels in practice

With a comprehensive plan such as Plan G, you generally pay the annual Part B deductible once at the start of the year, and after that most covered care costs you nothing out of pocket.

You show your Medicare card and your supplement card. Medicare pays, forwards the balance automatically, the supplement pays, and no bill arrives.

What it still will not do

A supplement pays your share of what Medicare covers. It cannot pay for prescriptions, routine dental, vision, hearing or long term custodial care, because Medicare does not cover those at all.

See the full list and what Medicare leaves out.