Medigap

Medigap, also called Medicare Supplement Insurance, is the private coverage that pays the cost-sharing Original Medicare leaves behind. It is sold by private carriers, but the benefit packages themselves are standardized by federal law into ten lettered plans. That standardization is the reason a Medigap plan with a given letter covers the same things at every carrier; the only meaningful differences across carriers for the same letter are price, customer service, and the underwriting posture each carrier takes outside the protected enrollment windows.

We lead with Medigap because it is the simplest path through Medicare for beneficiaries who can afford the premium and who value predictable out-of-pocket cost, broad provider access, and the ability to use any provider that accepts Medicare nationwide. That is not a recommendation that Medigap is right for every person. It is a statement that the standardized federal benefit structure makes Medigap the easiest piece of Medicare to reason about, and reasoning about Medicare is what this site is for.

The single most consequential rule in Medigap is the federal Medigap Open Enrollment Period. It is a six-month one-time window that opens when a beneficiary is both age 65 or older and enrolled in Medicare Part B. During this window, federal law requires carriers to issue any Medigap policy they sell, without medical underwriting, at the price they offer to other healthy applicants. Outside this window, federal protections largely end, and access depends on individual state rules that vary widely.

Below, the standardized plan letters are listed first. After them, the cross-cutting topics: pricing methods, guaranteed-issue triggers, the OEP itself, under-65 access, and household discounts. State-specific overlays live on the States hub.