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Health · Chapter 17 · Medigap

Medicare Supplement (Medigap) Basics

Definition
Private policies that fill Original Medicare's gaps (deductibles, coinsurance, extra hospital days). Only for Original Medicare enrollees — never with Medicare Advantage. One per person; no ancillary benefits (no dental/vision); no networks — nationwide coverage; benefits auto-adjust to Medicare's annual changes (30 days' notice).
In plain English
A caulk gun for Original Medicare's cracks — standardized, lettered, and strictly one per customer.
Easy to confuse with

These are what this term gets tested against — if you can't tell them apart cold, drill the contrast.

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Verified against primary sources · 2026-08-05