Understanding Medigap
How Medicare Supplement plans work and how to pick one.
What Medigap does
Medigap (also called Medicare Supplement Insurance) is a private policy that pays some of the costs Original Medicare doesn't — the Part A hospital deductible, coinsurance for extended hospital stays, the 20% Part B coinsurance, and (with some plans) the Part B deductible. It only works with Original Medicare, not with Medicare Advantage.
How the plan letters work
Medigap plans are standardized nationally and identified by letters (A, B, D, G, K, L, M, N — Plans C and F are only available if you were eligible for Medicare before January 1, 2020). Every insurer offering a given letter plan must cover the same benefits. Only price and service vary.
The most popular plans today
Plan G is the most comprehensive plan available to newly eligible enrollees — it covers everything except the small annual Part B deductible. Plan N has lower premiums with modest copays for doctor and ER visits. High-deductible Plan G trades a big deductible for a much lower monthly premium.
Best time to buy
Your Medigap Open Enrollment Period is a one-time 6-month window that starts when you turn 65 AND are enrolled in Part B. During this window, insurers must sell you any plan they offer at the best available rate — no medical questions, no denials. Missing this window means you may have to answer health questions and can be turned down in most states.
How prices are set
There are three pricing methods: community-rated (same for everyone regardless of age), issue-age (based on age when you buy), and attained-age (increases as you get older). Attained-age is the most common and usually starts cheapest — but rises the most over time.
How to compare
Pick your plan letter first based on the benefits you want, then shop that letter among insurers. Compare monthly premium, rate increase history, financial strength, and household discounts. The benefits are identical, so the cheapest reputable insurer with a stable rate history usually wins.
Medigap and drug coverage
Medigap does not cover prescription drugs. If you go with Original Medicare + Medigap, you'll need a stand-alone Part D plan to avoid the drug penalty and keep prescriptions affordable.