← Caregiver glossary · Insurance
Also: Medicare Supplement · Med Supp
Private supplemental insurance designed to cover the deductibles and coinsurance that original Medicare (Parts A + B) doesn't. Cannot be used with Medicare Advantage. Standardized into letter-named plans (Plan G, Plan N, etc.) that are identical across carriers — only the price varies.
Medigap policies are standardized by federal law — Plan G from one carrier covers exactly the same benefits as Plan G from any other carrier. Only the premium differs. This is unusual in US insurance and makes Medigap shopping straightforward: pick the plan letter that matches your coverage goals, then shop carriers on price alone (and on customer service / financial stability).
The most-popular plans are G and N. Plan G covers everything original Medicare doesn't except the Part B annual deductible ($257 in 2026). Plan N is slightly less expensive in premium but charges small per-visit copays + doesn't cover Part B excess charges (when a provider doesn't accept assignment). Plans like F (the most comprehensive) are no longer available to new Medicare enrollees who first became eligible after Jan 1, 2020.
The critical timing point: Medigap has guaranteed-issue rights ONLY during your initial Medigap enrollment period (6 months starting when you're 65 AND enrolled in Part B). After that window, Medigap carriers can use medical underwriting — meaning they can charge more, deny coverage based on pre-existing conditions, or refuse the application entirely. A few states (NY, CT, MA, ME) have year-round guaranteed-issue rules, but most don't. This is why the choice between Medicare Advantage and "Original + Medigap" at age 65 is consequential: choosing MA at 65 means your future ability to switch to Original + Medigap may be limited and expensive.
Medigap does not cover Part D drugs, dental, vision, hearing aids, or long-term care. For those, you need separate Part D, dental/vision plans, hearing-aid coverage, or LTC insurance.
When choosing how to fill the gaps in original Medicare. Most patients pick between "Original Medicare + Medigap + Part D" OR "Medicare Advantage" — generally not both.
Terms families frequently confuse with medigap.
Medicare Advantage REPLACES original Medicare; Medigap SUPPLEMENTS it. You can't have both at once. Medicare Advantage uses a private plan's network and cost-sharing; Medigap fills in original Medicare's deductibles and coinsurance while keeping the original's any-Medicare-provider freedom.
Medigap covers gaps in Parts A and B. Part D is separate prescription-drug coverage. A patient on Original + Medigap also needs a standalone Part D plan for prescription coverage; Medigap does not cover drugs.
See also: all glossary terms · conditions by name · step-by-step playbooks