Medicare Advantage vs. Medicare Supplement: An honest St. Louis comparison.

This is the biggest decision you'll make about Medicare. Most of the rest of it — when to enroll, how to pick a Part D plan, how to handle IRMAA — is detail work. The Advantage-vs-Supplement choice is the one that shapes which doctors you can see, what you pay every month, and how much it costs you when something serious happens.

I want to be careful with this article. We sell both Medicare Advantage and Medicare Supplement plans, and we have for a long time. There's no right answer for everyone. There's a right answer for you, and the work is figuring out which one it is.

Here's the honest version, in the way I'd walk you through it sitting across the desk.

The 60-second answer

Medicare Supplement (Medigap) plans pair with Original Medicare to cover most of what Medicare doesn't pay. You can see any doctor in the country who accepts Medicare. Predictable monthly cost, no networks, usually no dental or vision included.

Medicare Advantage (Part C) is a private all-in-one plan that replaces how you get your Medicare benefits — often a $0 plan premium, usually includes drug coverage and extras like dental and vision, but you're on a network, and your costs can be higher if you go outside it.

That's the quick frame. The rest of this article is the detail.

How they actually work

Original Medicare + Medicare Supplement + a Part D plan — the "three pieces" model.

Original Medicare is Part A (hospital) and Part B (doctor visits and outpatient care) run directly by the federal government. Original Medicare pays roughly 80% of the cost of covered services after the Part B deductible ($283 in 2026). The remaining 20% has no out-of-pocket maximum — meaning a long hospital stay or chemotherapy or a year of specialist visits could leave you exposed to thousands of dollars in cost-sharing, with no ceiling.

A Medicare Supplement (also called Medigap) is a private insurance policy you add to Original Medicare. It covers most of that 20% gap, depending on the letter plan you choose. The most common today is Plan G, which covers everything except the Part B deductible. There's also a high-deductible version of Plan G that costs less per month but has a deductible to meet first. Plan F is still in force for people who had it before 2020 but isn't available to people newly eligible for Medicare.

You also add a stand-alone Part D drug plan separately. So your monthly cost is: Part B premium + Supplement premium + Part D premium. In return, you get the most flexibility in the system — any provider in the country who accepts Medicare will take you.

Medicare Advantage (Part C) — the "all-in-one" model.

A Medicare Advantage plan is a private insurance plan that covers your Part A, your Part B, and almost always Part D drug coverage as a single bundled plan. Many include dental, vision, hearing, fitness, and over-the-counter benefits.

Advantage plans use networks. The plan picks the hospitals and doctors, sets the cost-sharing for each kind of visit, sets the prior-authorization rules, and sets the out-of-pocket maximum (a yearly cap on what you'll spend — for 2026, CMS caps the in-network maximum at $9,250, and some plans set theirs lower). When you stay in network, your costs are predictable. When you go out of network, your costs go up — sometimes a lot.

You still pay your Part B premium ($202.90/month in 2026 for most people) even when you're on a Medicare Advantage plan. Many Advantage plans have a $0 plan premium on top of that, but some have a monthly plan premium of $20, $50, or more depending on the plan and area.

The St. Louis network question

This is where the choice gets local. St. Louis has four big hospital systems: BJC HealthCare (Barnes-Jewish, Christian, Memorial East, Missouri Baptist, St. Louis Children's, Progress West, and others), Mercy, SSM Health (including Saint Louis University Hospital and a number of community hospitals), and SLUCare Physician Group.

If you go the Supplement route with Original Medicare, you can see any doctor in any of these systems — and any provider in the country who accepts Medicare. No referrals. No network restrictions.

If you go the Advantage route, you have to check the network. Not every Advantage plan covers every St. Louis system. Some plans are narrow — they're built around one hospital system and a small set of independent provider groups. Some are broader. None are unlimited.

The single most common mistake we catch in our office is somebody who already enrolled in an Advantage plan and didn't realize their primary care doctor was out of network — or that the specialist they've seen for ten years isn't covered. Confirm before you enroll. We do this check in every plan-fit conversation.

What it actually costs in 2026

Let me give you the honest picture of what each path actually costs in 2026.

Which one is "cheaper" depends entirely on how much care you use. A retiree with few medical needs may spend less on Medicare Advantage. A retiree with a complex medical history — frequent specialist visits, ongoing procedures, hospitalizations — may end up paying less total over a year on Original Medicare with a Supplement, because the monthly premium buys away the surprise costs.

The "$0 premium" footnote is important: it's the plan's premium that's $0. You still pay the Part B premium ($202.90/month in 2026 for most people). We're not allowed to advertise any plan as "free," and we don't.

Extras: dental, vision, hearing, OTC, fitness

This is the area where Medicare Advantage plans pulled ahead a decade ago and have stayed ahead since.

Most Advantage plans now include some level of dental allowance, vision allowance, hearing aid benefit, over-the-counter (OTC) allowance, and a fitness or gym-membership benefit. The dollar amounts and rules vary plan to plan. Some are generous. Some are token amounts. The benefit is real but uneven.

If you go the Original Medicare + Supplement route, those extras aren't included. You can buy them separately:

• Stand-alone dental and vision insurance is available from several carriers — and the math sometimes works better than a bundled Advantage benefit.
• Hearing aid programs exist outside Medicare.
• Fitness memberships you pay for yourself.

We help clients price out both versions when extras matter. It's not always clear which one wins until you actually run the numbers on your situation.

Can I switch later?

This is one of the most underappreciated parts of the decision.

From Advantage back to Original Medicare + Supplement

You can switch from an Advantage plan back to Original Medicare during AEP (Oct 15 – Dec 7) for the following January 1, or during MA-OEP (Jan 1 – Mar 31) for the following month. But picking up a Medicare Supplement after your first year usually requires you to go through medical underwriting in most states. That means the carrier looks at your health history and decides whether to issue the policy, and at what rate.

Missouri has a friendlier rule than most states for switching between same-letter Supplements during your anniversary window. We cover Missouri's anniversary rule in detail in Article 8. But going from Advantage back to a Supplement is a separate question, and it's not as easy as switching plans during AEP.

From Original Medicare + Supplement to Advantage

Easy. You can do it during AEP, with no underwriting. Your Supplement policy ends when your Advantage plan starts.

In other words: starting on Original Medicare + a Supplement leaves the door open in both directions. Starting on Advantage is harder to reverse later. That asymmetry is worth weighing.

When Advantage makes more sense

We see Medicare Advantage fit best for clients who:

• Have a tight monthly budget and don't want a Supplement premium added in.
• Are healthy and use little care today, with a family history that suggests that may continue.
• Want dental, vision, fitness, and OTC built in without buying separate policies.
• Have a primary care doctor and specialists who are all in the plan's network and don't travel much for care.
• Are comfortable with prior-authorization rules for some services.

When a Supplement makes more sense

We see Medicare Supplement fit best for clients who:

• Travel a lot (snowbirds, long-distance grandkids, multi-state retirement).
• Have an established relationship with specialists they don't want to risk losing.
• Have a family history of complex or expensive medical conditions.
• Value predictable monthly costs over a low premium with variable out-of-pocket.
• Don't want to deal with network rules or prior authorizations.

These aren't rigid rules. Plenty of clients fit both profiles in different ways. The work is figuring out which side of the line your specific situation lives on.

What to do next

If you're researching this decision, the most useful conversation is probably 30 minutes on the phone with someone who can run real numbers for your situation, your doctors, and your prescriptions. Plenty of people make this decision by sitting across the desk with a licensed insurance agent and walking through the trade-offs. That's what we do.

Call us at (314) 248-6500. No fee, no pressure, no sales pitch — that's the rule of the house. We sell both Advantage and Supplements, and we'll tell you honestly which one fits you. If neither one we offer is right for your situation, we'll tell you that, too.

I've been helping people with Medicare in St. Louis since 2013. The Advantage-vs-Supplement question is the one I've answered the most. It's the heart of the Medicare conversation.