Understanding Medicare Supplement (Medigap)

What Is a Medicare Supplement Plan?

A Medicare Supplement plan — you'll also hear "Medigap," same thing — is private insurance that works alongside Original Medicare, not instead of it. Original Medicare pays its share first (roughly 80% of covered medical costs), and your Supplement helps pay your share: the remaining 20%, deductibles, and coinsurance.

That matters because Original Medicare alone has no yearly limit on what you might pay out of pocket. A Supplement puts a shape on those "what ifs" in exchange for a predictable monthly premium.

How the Pieces Fit Together

• Original Medicare (Parts A and B) — your foundation. Hospital and medical coverage from the federal government.
• Medicare Supplement — pays your share of Medicare-covered costs.
• A Part D drug plan — Supplements do not include prescription coverage, so you add a stand-alone drug plan.

Three pieces, and you're covered — this combination is often called the "build your own" path, compared with the all-in-one Medicare Advantage path.

Plans Are Standardized — the Letters

Supplement plans come in standardized versions named by letter (Plan G and Plan N are the ones you'll hear most). Here's the helpful part: a given letter is identical no matter which insurance company sells it. One company's Plan G covers exactly what another company's Plan G covers — only the price and the company's service differ. That turns shopping into a much simpler question: which letter fits you, and who offers it at a fair, stable price in your state.

The Freedom Part: Any Doctor, Any State

Supplements have no networks. If a doctor or hospital anywhere in the U.S. accepts Medicare, your coverage works there — all 50 states, no referrals, no "is my doctor on the list?" This is why Supplements come up constantly in snowbird and traveler conversations: summer doctor in Utah, winter doctor in Arizona, both covered the same way. (Splitting time between states? See our moving and snowbird guides.)

The Enrollment Window That Really Matters

Here's the single most important thing on this page: you get a 6-month Medigap Open Enrollment Period that starts when you're 65 or older and enrolled in Part B. During that window, companies must accept you regardless of your health history — no health questions, no denials.

After the window closes, applying for a Supplement usually involves health questions, and coverage can be declined or cost more depending on your health (rules vary by state and situation). People who might want a Supplement someday are usually best served by getting it when the door is wide open. This one deadline shapes more Medicare outcomes than almost any other.

The Trade-Offs, Honestly

• Higher monthly premium than many Medicare Advantage plans — you're trading monthly cost for predictability.
• No extras: Supplements generally do not include dental, vision, or hearing. Those gaps can be filled separately — see our ancillary coverage page.
• No drug coverage: plan on adding a Part D plan.