The short answer: these are two different ways of covering the gaps in Original Medicare, and you pick one, not both. Medicare Advantage (Part C) replaces how your Medicare is administered, usually costs less per month, and works through a network. Medigap sits alongside Original Medicare, usually costs more per month, and lets you use any provider in the country who accepts Medicare.

Neither is better. They fail in different directions, and which failure you can live with is the actual decision.

  • Medigap = Original Medicare + a supplement. Any Medicare provider, predictable costs, higher monthly premium. Part D bought separately.
  • Medicare Advantage = a private plan that administers your Medicare. Network, referrals and prior authorisation, lower monthly premium, out-of-pocket maximum. Drug coverage usually built in.
  • The switch back from Advantage to Medigap is the part people do not see coming.

What is actually different?

Where you can go. Medigap follows Original Medicare, so any provider in the country who accepts Medicare works — no network, no referrals. Medicare Advantage plans have networks, and going outside one costs more or is not covered at all.

How you pay. Medigap generally means a higher monthly premium and very little at the point of care. Advantage generally means a low or zero monthly premium and copays as you use it, with an annual out-of-pocket maximum that Original Medicare alone does not have.

Who decides on care. Advantage plans can require referrals and prior authorisation. Original Medicare with a Medigap does not.

Drugs. With Advantage, drug coverage is usually included. With Medigap you buy a separate Part D plan and check your prescriptions against its .

Which one is right for me?

Nobody can answer that from a webpage, and any page that tries is selling you something. But the questions that actually decide it are short:

  • Do you have doctors or a hospital you are not willing to change?
  • Do you travel, or spend part of the year in another state?
  • Would a low monthly premium with occasional copays suit your budget better than a steady higher premium with few surprises?
  • Do you take prescriptions that would need checking against a plan's drug list?
  • Would having to get referrals and prior authorisation frustrate you, or not bother you?

When can I change my mind?

  • , October 15 to December 7: switch Advantage plans, move between Original Medicare and Advantage, or join or change a Part D plan. Changes take effect January 1.
  • Medicare Advantage Open Enrollment, January 1 to March 31: if you are already in an Advantage plan you get one change — to a different Advantage plan, or back to Original Medicare.
  • A may open outside those windows if something specific happens, such as moving out of your plan's service area or losing other coverage.

None of these give you a guaranteed right to buy a Medigap policy. That is the asymmetry worth carrying away from this page.

What should I do next?

  1. Write down your doctors and your prescriptions. Everything below depends on that list, and it is the step people skip.
  2. Decide which failure you would rather have — paying more each month, or being limited on where you can go.
  3. Check what is actually available in your county. Advantage and Part D availability is set county by county, not by state.
  4. Compare the two routes side by side with the plan comparison tool.
  5. If you are new to all this, start with the four parts in plain English.

Plan availability is a county-level question, which is why the local pages exist: Bergen County, New York City and Philadelphia. New York in particular treats Medigap differently from New Jersey, and that difference matters here. You can also see how enrollment works in each state I am licensed in.

Where these rules come from

The structure of these two routes is federal. What varies — which plans exist, what they cost, which providers are in network — is county-level and changes every contract year, so confirm it for your own address rather than from any page:

Last reviewed: 28 July 2026. This page explains how the two routes differ. It does not name plans, carriers or prices, because those are set annually and vary by county — and because I do not carry every plan available in your area, which is why the disclosure at the bottom of every page on this site exists.