Medicare Advantage (Part C) bundles your Medicare coverage into one plan from a private insurer, often with low or zero premiums and built-in extras like dental, vision, and prescription drugs — but it usually limits you to a network of doctors and hospitals. Medicare Supplement (also called Medigap) works alongside Original Medicare to cover out-of-pocket costs like copays and deductibles, giving you nationwide doctor access with no networks but a higher monthly premium and no built-in drug or dental coverage. The right choice depends on your health needs, your budget, how often you travel, and how predictable you want your costs to be.

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How They Actually Work

The two plans solve the same problem — Medicare’s coverage gaps — in fundamentally different ways.

Medicare Advantage (Part C)

You replace Original Medicare with a private plan that delivers your Part A, Part B, and usually Part D benefits in one package. Most Advantage plans operate as HMOs or PPOs — meaning you typically need to use in-network doctors and may need referrals for specialists. In exchange, you often get a low or $0 monthly premium and extra benefits Original Medicare doesn’t cover, like routine dental, vision, hearing aids, gym memberships, and over-the-counter allowances.

The trade-off is variability. You’ll have copays and coinsurance every time you use care, and your annual out-of-pocket maximum can be several thousand dollars before the plan covers 100%.

Medicare Supplement (Medigap)

You keep Original Medicare and add a Medigap policy that fills in the deductibles, copays, and coinsurance Original Medicare leaves behind. There are no networks — any doctor or hospital in the US that accepts Medicare accepts your Medigap plan. You pay a higher monthly premium, but your costs at the point of care are far more predictable. Most Medigap plans cover nearly all your out-of-pocket costs after Medicare pays its share.

Medigap doesn’t include drug coverage, so you’ll need a separate Part D plan. It also doesn’t include dental, vision, or hearing — those would need standalone policies.

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Side-by-Side Comparison

Feature	Medicare Advantage	Medicare Supplement
Monthly premium	Often $0–$50	Typically $100–$300+
Doctor network	Limited (HMO/PPO)	Any provider accepting Medicare
Referrals for specialists	Sometimes required	Never required
Out-of-pocket costs at the doctor	Copays and coinsurance per visit	Minimal to none, depending on plan
Annual out-of-pocket maximum	Yes (capped by federal limit)	Effectively very low with most plans
Prescription drug coverage	Usually included	Not included — buy separate Part D
Dental, vision, hearing	Often included	Not included
Coverage when traveling	Usually limited to network area	Nationwide
Underwriting to enroll later	None — guaranteed acceptance during enrollment periods	Required after your first enrollment window

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Who Should Pick Medicare Advantage?

• People who are generally healthy and don’t visit the doctor often
• People who want one card and one plan instead of juggling multiple policies
• People comfortable with networks and referrals
• People who value extras like dental, vision, and gym memberships
• People who can absorb the year-to-year variability in copays
• People who stay close to home and don’t travel often

Who Should Pick Medicare Supplement?

• People who want maximum doctor and hospital choice
• People with chronic conditions or expected high care use
• People who travel frequently or split time between states
• People who prefer predictable monthly costs over low premiums
• People who don’t want to worry about referrals or network changes
• People who want the same plan to last for life without annual reshuffling

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The One-Way-Door Problem No One Talks About

When you first become Medicare-eligible, you can buy any Medigap plan with no health questions asked. After that window closes, insurance companies in most states can deny you a Medigap policy or charge more based on your health. Missouri allows medical underwriting for Medigap outside of guaranteed-issue periods.

This means switching from Medicare Advantage to Medigap later in life can be difficult or impossible — especially after a serious diagnosis. Switching the other direction (Medigap to Advantage) is generally easy. This asymmetry is one of the most overlooked factors in the decision.

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Frequently Asked Questions

Can I switch between Medicare Advantage and Medicare Supplement later?

You can switch from Medicare Supplement to Medicare Advantage during the Annual Enrollment Period (October 15 – December 7) without medical underwriting. Switching the other direction — from Medicare Advantage back to Original Medicare with a Medigap plan — is more complicated. While you can drop Medicare Advantage during AEP or the Open Enrollment Period (January 1 – March 31), most states (including Missouri) allow Medigap insurers to medically underwrite your application, meaning they can deny coverage or charge more based on your health history. This is why your initial choice matters more than people realize.

Which is cheaper, Medicare Advantage or Medicare Supplement?

It depends on how much care you actually use. Medicare Advantage almost always has a lower monthly premium — many plans are $0 — but you pay copays and coinsurance every time you use medical services, up to your annual out-of-pocket maximum. Medicare Supplement has a higher monthly premium, often $100–$300, but very low costs when you actually receive care. For someone with significant medical needs, Medigap can be cheaper overall. For someone in great health who rarely uses care, Advantage usually wins. A licensed advisor can run the math against your real prescriptions and expected care use.

Do I need Part D with Medicare Supplement?

Yes, if you take prescription medications or want protection against future drug costs. Medicare Supplement plans don’t include prescription drug coverage, so you’ll need to enroll in a standalone Part D plan to avoid the late enrollment penalty and to have coverage when you need it. Even people who take no medications today are usually advised to enroll in a low-premium Part D plan during their Initial Enrollment Period to avoid the penalty later — that penalty is permanent and grows every month you go without creditable drug coverage.

Can I keep my doctor with Medicare Advantage?

Only if your doctor is in your specific Medicare Advantage plan’s network. Networks vary widely by carrier and by plan, and they can change from year to year — a doctor who’s in-network this year may be out-of-network next year. Before enrolling in any Medicare Advantage plan, confirm directly with your doctor’s billing office that they currently accept that exact plan. With Medicare Supplement, this isn’t an issue: any provider in the US that accepts Medicare also accepts your Medigap plan.

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Still not sure which path is right for you? Schedule a free, no-pressure consultation with The Advocate Group → We’re independent, which means we compare plans across multiple top-rated carriers and recommend what actually fits your life — not what pays us the highest commission.