Medicare Part B vs. Part C: What Actually Differs

Part B and Part C are not two rival plans you pick between on equal terms. Part B is the medical insurance half of Original Medicare, covering doctor visits and outpatient care. Part C, better known as Medicare Advantage, is a private-plan alternative to Original Medicare that bundles Parts A and B, and usually Part D. The real decision is whether you want Original Medicare (Parts A and B, usually with a Medigap and a drug plan) or a Medicare Advantage plan that wraps everything into one. Here is how to tell which fits you.

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TL;DR

• Part B is medical insurance (doctors, outpatient care, equipment, preventive services). Part C is a private Medicare Advantage plan that replaces how you receive Parts A and B.
• Yes, Part C is Medicare Advantage. The two names mean the same thing.
• You need both Part A and Part B to join a Medicare Advantage plan, and you keep paying your Part B premium.
• Original Medicare lets you see any doctor in the U.S. who accepts Medicare. Medicare Advantage plans may require you to use a network.
• You can’t buy Medigap to go with a Medicare Advantage plan. Medigap works only with Original Medicare.

Table of Contents

• What Part B covers
• What Part C is (and why it has two names)
• Part B vs. Part C side by side
• Drug coverage: Part D in each path
• Medigap: the piece that only works with Part B
• Who can enroll in Part C, and when
• How to decide between Part B alone and Part C
• Our perspective
• Get a side-by-side comparison for Colorado
• Common mistakes when comparing Part B and Part C
• FAQ
• Sources

What Part B covers

Part B is medical insurance. According to Medicare, it covers services from doctors and other health care providers, outpatient care, durable medical equipment, and many preventive services. Think office visits, specialist appointments, lab work, outpatient surgery, wheelchairs and walkers, and screenings.

Part A is the hospital side. Together, Parts A and B form Original Medicare, the federal program. If you want a deeper walk through the pair, our guide to Medicare Part A and Part B covers coverage and enrollment step by step.

What Part B costs

Part B is optional and carries a monthly premium. The standard premium was $202.90 a month in 2026, up from $185.00 in 2025. Higher earners pay an income-related adjustment on top. CMS publishes new amounts each year, so check the current figure on Medicare.gov before you budget.

Original Medicare also has a deductible and coinsurance, and it has no yearly cap on what you can owe unless you add other coverage. That is why many people pair it with a Medigap policy, which we cover below.

What happens if you skip Part B

If you don’t sign up when you’re first eligible, you may face a late enrollment penalty. Some people can delay without penalty, for example when they have qualifying employer coverage, but that depends on your situation. Our article on Medicare late enrollment penalties explains how the penalty works and how to avoid it.

What Part C is (and why it has two names)

Is Part C the same as Medicare Advantage? Yes. Medicare describes Medicare Advantage as sometimes called Part C. The “C” is just its place in the lettering of Medicare’s parts. Insurance ads say “Medicare Advantage,” and government publications often say “Part C.”

A Medicare Advantage plan is sold by a private insurance company that follows Medicare’s rules. It must cover what Original Medicare covers, and most plans add more. The Medicare & You handbook notes that most Medicare Advantage plans include prescription drug coverage, so members generally don’t need a separate drug plan.

One point trips people up: Part C is not a replacement for Part B enrollment. You still need Part A and Part B to join, and you must still pay your monthly Part B premium on top of any premium the plan charges. Many plans charge no additional premium, but that does not erase the Part B premium.

Part B vs. Part C side by side

Feature Part B (Original Medicare) Part C (Medicare Advantage) What it is Federal medical insurance, part of Original Medicare Private plan that bundles Parts A and B, usually D Who runs it The federal government Private insurers approved by Medicare Doctor choice Any doctor or hospital in the U.S. that accepts Medicare May require network doctors for non-emergency, non-urgent care Drug coverage None built in; add a standalone Part D plan Most plans include it Extra coverage Add Medigap (supplement) if you want Cannot add Medigap Premium Monthly Part B premium Part B premium plus any plan premium Rules Same nationwide Vary by plan and by county

The provider difference is the one most people feel first. Medicare explains that Medicare Advantage plans may require you to use doctors in the plan’s network for non-emergency and non-urgent care, while Original Medicare lets you use any doctor or hospital in the country that accepts Medicare. If your cardiologist, or the hospital you’d choose in an emergency, matters to you, check network status before you enroll, not after.

Drug coverage: Part D in each path

With Original Medicare, drug coverage is separate. Part D is either a standalone plan for people with Original Medicare or bundled into most Medicare Advantage plans. So the Part B vs. Part C question is often really a question about how you want to handle prescriptions.

If you take several medications, the formulary (the plan’s list of covered drugs) and your pharmacy matter more than the plan’s name. Our overview of what Medicare Part D is explains formularies and premiums. A drug plan that covers your medications at a fair price can matter more than any extra benefit.

Medigap: the piece that only works with Part B

Medigap, also called Medicare Supplement, helps pay costs that Original Medicare leaves to you, such as deductibles and coinsurance. Medicare states plainly that you can’t buy Medigap to cover out-of-pocket costs in a Medicare Advantage plan. It helps only with Original Medicare.

That makes this the biggest fork in the road:

• Original Medicare + Medigap + standalone Part D. Higher, more predictable premiums, no network restrictions, and cost-sharing that a supplement such as Plan G or Plan N can soften.
• Medicare Advantage. Often a lower monthly premium, one card, extras such as dental or vision in many plans, but networks, prior authorization and plan-specific copays.

Medicare & You describes Advantage plans as bundling coverage, possibly requiring network use and prior authorization, with out-of-pocket costs that usually differ from Original Medicare. For a side-by-side look at cost structures, see our page on Medicare Advantage vs. Medigap.

Coverage questions don’t stop at doctor visits, either. Whether a specific treatment is paid for, such as Medicare coverage of PRP therapy, depends on the coverage rules for that service, so ask about any treatment you’re planning before you assume it’s included in either path.

Who can enroll in Part C, and when

To join a Medicare Advantage plan you need both Part A and Part B. You can join during your Initial Enrollment Period, which generally lasts 7 months: the three months before the month you turn 65, your birthday month, and the three months after.

Medicare Advantage plans are also tied to where you live, since each plan serves specific counties. If you move out of your plan’s service area, you’ll need to choose a new plan.

After your first window, the main yearly opportunity is the fall Annual Enrollment Period, which runs from October 15 to December 7 each year. Other special enrollment periods exist for events such as moving or losing other coverage. Our Medicare enrollment periods guide lays out each window. If you are in Colorado and approaching 65, our piece on the 7-month initial enrollment clock shows how the timing works in practice.

How to decide between Part B alone and Part C

There is no universal winner. Work through these questions in order.

1. Which doctors and hospitals do you want to keep? List them. Check whether each takes Original Medicare, then whether each is in the network of any Advantage plan you’re considering.
2. What medications do you take? Look up each one against a plan’s formulary. This applies to a standalone Part D plan and to an Advantage plan with drug coverage.
3. How do you feel about variable costs? Original Medicare with a Medigap plan is built around predictable costs. Advantage plans use copays that vary by service, so look at the plan’s maximum yearly out-of-pocket amount.
4. Do you travel or split your year between states? Original Medicare works nationwide. Advantage networks can be local.
5. Do you want extras? Many Advantage plans bundle dental, vision and hearing. With Original Medicare, those are typically separate policies.
6. Can you afford to switch back? If you start on Advantage and later want a Medigap policy, insurers in many cases can review your health before approving you. Ask about your rights before you move.

There is a timing trap in point 6 worth knowing before you choose: your easiest moment to get a Medigap policy is usually when you first have Part B. A decision made at 65 can shape your options for years.

Our perspective

Most people who come to us at 65 ask the same question: “Which part do I pick?” The better question is: “Which way do I want to use Medicare?” Part B is the foundation for almost everyone. Part C is one way of building on it, and Medigap with a drug plan is the other.

We are independent, licensed brokers working across multiple carriers, so we don’t push one design. What we do is match your doctors, your prescriptions and your budget to the plans available in Colorado, and we show you the trade-offs in plain language. For many Castle Pines clients, that conversation settles in an hour what weeks of mailers could not.

We also stay with you after you enroll. Plans change every year, formularies shift and networks get redrawn, so we review your coverage annually and help with claims, appeals and grievances when something goes wrong. Our view: a good Medicare decision is one you revisit, not one you make once and forget.

Zach

Get a side-by-side comparison for Colorado

If you want to see Original Medicare with a Medigap plan next to Medicare Advantage options for your county, we can build that comparison with you. Our service is no direct cost to you, because carriers pay us when you enroll. We cover Medicare Advantage plans, Medigap plans including Plan G and Plan N quotes, and Part D drug plans.

Turning 65 soon? Our Medicare help for Castle Pines residents starts with your enrollment window. You can also see everything we offer on our services page, or start from our Medicare planning page.

Common mistakes when comparing Part B and Part C

Treating Part C as a way to avoid Part B. It isn’t. You need Part B to join, and you keep paying for it.

Judging only by the monthly premium. A plan with no additional premium can still carry copays, prior authorization rules and network limits. A plan with a higher premium can cost less overall for someone who uses a lot of care. Compare total expected cost for your usage.

Ignoring the drug list. Premium and formulary together decide what you pay for prescriptions. Check both each year.

Assuming you can add Medigap later without conditions. Medigap works only with Original Medicare, and your ability to buy one later depends on timing and rules in your state. Ask before you enroll in an Advantage plan.

Setting it and forgetting it. Advantage plans can change benefits, networks and costs every January. Review the notice your plan sends in the fall, and compare again during the Annual Enrollment Period.

For a wider view of how all four parts connect, our guide to Medicare Parts A, B, C and D is a good next read.

FAQ

Is Medicare Part C called Medicare Advantage?

Yes. Medicare Advantage plans are sometimes called Part C or MA plans. They are offered by Medicare-approved private companies that must follow rules set by Medicare. The two names refer to the same type of coverage.

Do I still pay the Part B premium if I have Part C?

Yes. You must have Part A and Part B to join a Medicare Advantage plan, and you continue paying your monthly Part B premium. The plan may add its own premium on top, though many plans charge none. The standard Part B premium was $202.90 in 2026, and it changes each year.

Can I keep any doctor with Part C?

Not always. Some Medicare Advantage plans require you to use network doctors for non-emergency and non-urgent care. Original Medicare lets you see any doctor or hospital in the U.S. that accepts Medicare. Check each doctor against a plan’s network before you enroll.

Can I buy a Medigap policy with a Medicare Advantage plan?

No. Medigap helps pay out-of-pocket costs in Original Medicare only, and you can’t buy it to cover costs in a Medicare Advantage plan. If you want a supplement such as Plan G or Plan N, you’d stay with Original Medicare and add a standalone drug plan.

When can I join a Part C plan?

Most people first join during their Initial Enrollment Period, which generally lasts 7 months and starts 3 months before the month you turn 65. You can also make changes during the fall Annual Enrollment Period and certain special enrollment periods. Check Medicare.gov for the current schedule.

Sources

• Parts of Medicare | Medicare.gov
• How does Medicare work? | Medicare.gov
• Joining a plan | Medicare.gov
• Medicare & You handbook | Medicare.gov
• 2026 Medicare Parts A & B Premiums and Deductibles | CMS
• Is PRP Therapy Covered by Medicare or Private Insurance?

Recommended

• Medicare Parts A, B, C & D Explained
• Medicare Part A and Part B: Coverage, Differences & Enrollme
• Medicare Advantage Plans
• Medicare Guide