Can I switch from Medicare Advantage to Medigap later?

You can return to Original Medicare during certain windows, but buying Medigap is the harder half. Outside your 6-month Medigap open enrollment period, most states let insurers use medical underwriting, so you can be charged more or declined. A 12-month trial right exists if you joined Medicare Advantage when first eligible.

Do I still need Parts A and B with either one?

Yes. Both paths are built on Original Medicare, so you enroll in Parts A and B first and then choose how to cover the rest.

Which one is cheaper?

It depends entirely on how much care you use. Medigap costs more in monthly premiums and far less at the point of care. Medicare Advantage often costs little or nothing extra per month and more as you use it. Compare total yearly cost for your own situation rather than premiums alone.

Can I have both Medigap and a Medicare Advantage plan?

No. Medigap only works alongside Original Medicare, and it pays nothing toward Medicare Advantage costs. Anyone selling you a Medigap policy while you hold a Medicare Advantage plan is selling you something you cannot use.

Medicare 101

Medicare Advantage vs. Medicare Supplement: How to Choose

This gets explained as though one answer fits everyone, and it does not. Three things decide it: how each option works with Original Medicare, what each actually costs over a year, and how much freedom each leaves you. The factor people most regret overlooking is none of those. It is a timing rule.

Forrest Klein · Licensed Insurance Agent

Last reviewed November 3, 2026

The short answer

Both build on Original Medicare, which is Medicare Part A (hospital) and Part B (medical), and this page is part of our Medicare 101 series. The difference is how. A Medicare Supplement, also called Medigap, works alongside Original Medicare and pays the copays, coinsurance and deductibles it leaves you. A Medicare Advantage plan REPLACES how you receive those benefits, delivering them through a private insurer approved by Medicare. You cannot hold both, and Medigap does not work with a Medicare Advantage plan.

How Medicare Supplement works

Medigap pays after Original Medicare pays. The plans are standardized and lettered, so Plan G from one insurer has identical benefits to Plan G from another and only price and service differ. That makes shopping unusually simple: find the letter you want, then buy it from whoever is cheapest. Medigap includes no prescription drug coverage, so most people add a standalone Part D plan.

Plan G: The common choice for people new to Medicare. Covers your share of Medicare-approved costs except the Part B deductible, $283 in 2026. Pay that once a year and covered care is generally free after it.
Plan N: Lower premiums than Plan G in many areas. In exchange you pay the Part B deductible plus copays, up to $20 on some office visits and up to $50 on emergency visits that do not lead to admission.
Plan F: Covers the Part B deductible too, but is closed to anyone who became eligible for Medicare on or after January 1, 2020.
No networks: Any doctor or hospital in the U.S. that accepts Medicare, with no referrals.

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How Medicare Advantage works

A Medicare Advantage plan bundles hospital and medical coverage, and usually drugs, into a single plan with a single card. Every plan has a service area, and most run a provider network, which is the central trade-off. Many also require prior authorization before certain services. Most add benefits Original Medicare does not cover at all, such as dental, vision and hearing coverage. HMO plans tie you tightest to the network; a PPO lets you go outside it for more money.

HMO: In-network providers except in emergencies, and referrals are often needed to see a specialist.
PPO: Out-of-network care is allowed, usually at a higher cost to you.
Prior authorization: Some services need the plan's approval before you receive them.

What each actually costs

Costs Compared properly means looking at the whole year, not the monthly figure. With Medigap you pay the Part B premium, $202.90 as the 2026 standard, plus the Medigap premium, plus a drug plan. Medigap pricing varies by plan letter, age, location and insurer. With Medicare Advantage you still pay the Part B premium and the plan may add its own, though many charge nothing extra. The difference is where the rest of the money goes: Medigap front-loads it into predictable monthly premiums, Medicare Advantage spreads it into copays you only pay when you use care.

Original Medicare alone has no cap: No annual limit on what you can owe. This is the main reason Medigap exists.
Medicare Advantage always has one: Every plan must cap your yearly out-of-pocket costs for covered services, and many set theirs below the federal maximum.
Drug costs are capped either way: Once your out-of-pocket spending on covered Part D drugs reaches $2,100 in 2026, rising to $2,400 in 2027, you pay nothing more that year.

Side by side

The same seven questions, answered both ways. Most people find one column obviously describes them.

Doctors: Medigap: any provider who accepts Medicare. Advantage: usually a network.
Referrals: Medigap: never. Advantage: often, depending on plan type.
Monthly cost: Medigap: higher. Advantage: often lower, sometimes nothing beyond Part B.
Cost when you need care: Medigap: low, close to nothing with Plan G. Advantage: copays and coinsurance until you hit the cap.
Drug coverage: Medigap: add a separate Part D plan. Advantage: usually built in.
Dental and vision: Medigap: not included. Advantage: frequently included.
Travel: Medigap: works anywhere in the U.S. Advantage: limited outside the service area.

The timing rule people regret

Here is the part that is not about money. You can join a Medicare Advantage plan during your Initial Enrollment Period, during Open Enrollment each fall, or with a Special Enrollment Period. Medigap does not work that way: its open enrollment period lasts 6 months and starts the first month you are both 65 or older and enrolled in Part B. Inside it, an insurer must sell you any Medigap plan it offers at its standard price, whatever your health. After it closes, most states allow medical underwriting, meaning health questions, higher prices, or refusal. The consequence catches people out: choose Medicare Advantage first and decide years later that you want Medigap, and you may simply not be able to get it. A handful of states grant broader rights, and there is a 12-month trial right if you joined Medicare Advantage when first eligible, but neither is something to count on without checking your own state.

Which one probably fits you

Neither is better in the abstract. The honest test is what you value and how you use care, not which has the lower premium. Medigap may fit if you travel, see many specialists, or simply want to know what a bad year costs. If you have Medicaid as well as Medicare, a plan built for both may fit better than either.

Medigap suits you if: You want any doctor who accepts Medicare, with no referrals, you would rather pay predictably each month than face surprises, or you travel and spend part of the year elsewhere.
Medicare Advantage suits you if: You want lower monthly costs and are comfortable inside a network, you want dental, vision and hearing bundled in, or you prefer one card and one company for everything.
If you have Medicaid: You may qualify for a Dual Special Needs Plan built specifically for people with both programs, which usually beats either option above.