If you’re turning 65, retiring, or simply tired of unpredictable Medicare bills, you’ve probably run into the term “Medigap” more than once this year. With Medicare Open Enrollment approaching, insurance mailers, TV ads, and well-meaning relatives are all pushing opinions about Medigap, Medicare Advantage, and which one is “better.” This guide cuts through the noise and explains exactly what Medigap is, how it works in 2027, what it costs, and how to decide if it’s right for you.
In This Guide
What Is Medigap Insurance?
Medigap, formally known as Medicare Supplement Insurance, is a private insurance policy designed to work alongside Original Medicare (Part A and Part B). Medicare itself only pays a percentage of most covered services — typically 80% for Part B services — which leaves beneficiaries responsible for the remaining coinsurance, copayments, and deductibles. Medigap policies are built specifically to pick up some or all of that remaining “gap,” which is where the name comes from.
Medigap is sold exclusively by private insurance companies, but every plan must follow federal and state rules that standardize the benefits. That’s a critical distinction from Medicare Advantage, where benefits vary widely by carrier and even by zip code. A Medigap Plan G from one company, for example, covers exactly the same core benefits as a Plan G from another company — the only real differences are price, customer service, and financial stability of the insurer.
How Medigap Works With Original Medicare
Medigap only works alongside Original Medicare — it cannot be paired with a Medicare Advantage plan. Here’s the basic flow when you have Medicare plus Medigap:
- You see any doctor or hospital nationwide that accepts Medicare (no networks or referrals).
- Medicare pays its share of the approved amount first.
- Your Medigap insurer automatically pays some or all of the remaining balance, depending on your plan letter.
- In many cases, you owe little to nothing out of pocket for covered services.
Because Medigap has no provider networks, it’s especially popular with retirees who travel, split time between two states, or simply want the freedom to see specialists without a referral. For a deeper look at how this compares with the managed-care model, see our breakdown of Medigap vs. Medicare Advantage costs over 10 years.
The Medigap Plan Letters (A Through N)
In most states, Medigap plans are standardized into lettered categories: A, B, D, G, K, L, M, and N (Plans C and F are largely closed to people newly eligible for Medicare on or after January 1, 2020). Each letter offers a fixed set of benefits set by the federal government — insurers cannot add or remove benefits from a lettered plan, they can only compete on price and service.
| Plan | Popularity | Best For |
|---|---|---|
| Plan G | Most popular for new enrollees | Near-total coverage; only Part B deductible left unpaid |
| Plan N | Fast-growing, lower premium | Budget-conscious shoppers willing to pay small copays |
| Plan A | Basic tier | Minimal coverage, lowest premiums |
| Plan F | Closed to new enrollees since 2020 | Existing policyholders only (first eligible before 2020) |
| Plan K / L | Cost-sharing plans | Lower premiums with an annual out-of-pocket limit |
For a full side-by-side comparison of what each letter actually covers, read our detailed breakdown: Medigap Plan Letters Explained: A vs. B vs. F vs. G vs. N. If you’re deciding between the two most popular options, we also have a focused comparison of Plan G vs. Plan N.
When You Can Enroll in Medigap
Unlike Medicare Advantage and Part D, Medigap does not run on the October 15–December 7 Annual Enrollment Period. Instead, Medigap has its own one-time 6-month Medigap Open Enrollment Period that begins the month you turn 65 and are enrolled in Part B. During this window, insurers must sell you any Medigap policy they offer, at the best available price, regardless of your health history.
Outside that window, insurers in most states can use medical underwriting to deny coverage or charge more based on pre-existing conditions — unless you qualify for a Guaranteed Issue Right. These two topics are complex enough that we’ve dedicated full guides to each:
What Medigap Costs in 2027
Medigap premiums vary significantly by state, age, gender, tobacco use, and pricing method (community-rated, issue-age-rated, or attained-age-rated). Nationally, Plan G premiums have generally ranged from roughly $120 to $300+ per month depending on location and age, while Plan N tends to run lower. Because pricing differs so much by state, we’ve built a dedicated state-by-state breakdown: How Much Does Medigap Cost in 2027? State-by-State Premium Guide.
Medigap vs. Medicare Advantage
This is the single biggest decision most new Medicare beneficiaries face. Medigap generally means higher monthly premiums but very low or no out-of-pocket costs at the point of care, plus nationwide provider access. Medicare Advantage generally means low or $0 premiums but network restrictions, referrals, and variable out-of-pocket costs that can add up quickly during a serious illness. We go deep on the 10-year cost math in our companion article, Medigap vs. Medicare Advantage: Which Costs Less Over 10 Years?
How to Choose a Medigap Plan
- Start with your health needs. Frequent specialist visits or a chronic condition often favor richer plans like G.
- Compare Plan G and Plan N carefully. Plan N has a lower premium but adds small copays — our Plan G vs. Plan N comparison shows the break-even math.
- Check carrier financial ratings (A.M. Best, S&P) since you may hold this policy for decades.
- Time your enrollment around your 6-month Open Enrollment window whenever possible to avoid underwriting.
- Re-shop periodically. Because benefits are standardized, you can often switch carriers for the same Plan G coverage at a lower price — see Switching Medigap Plans.
Ready to compare Medigap rates from top-rated carriers in your area?
Frequently Asked Questions
- What is Medigap insurance?
- Medigap, also called Medicare Supplement Insurance, is a private policy that helps pay the out-of-pocket costs — copayments, coinsurance, and deductibles — that Original Medicare leaves behind.
- Can I have Medigap and Medicare Advantage at the same time?
- No. Insurers cannot legally sell you a Medigap policy while you’re enrolled in a Medicare Advantage plan, except when you’re actively switching back to Original Medicare.
- Does Medigap cover prescription drugs?
- No. Current Medigap policies do not include drug coverage. You’ll need a standalone Medicare Part D plan alongside your Medigap policy.
