The core difference: how each plan works with Medicare

A Medicare Supplement plan (also called Medigap) works alongside Original Medicare. You keep your Medicare Part A and Part B coverage, and the supplement plan pays some of the costs Medicare doesn't cover — like copayments, coinsurance, and deductibles. You can see any doctor or hospital that accepts Medicare.

A Medicare Advantage plan (Part C) replaces Original Medicare entirely. The insurance company becomes your Medicare provider. Instead of Medicare paying the doctor, the Advantage plan does. You must use doctors and hospitals in the plan's network, with rare exceptions for emergencies.

The choice between them shapes where you go for care, what you pay, and how much flexibility you have. Neither is universally "better" — it depends on your health, your doctors, and what you can afford.

Key Takeaways

  • Supplement plans let you keep Original Medicare and see any Medicare-accepting doctor; Advantage plans replace Medicare and limit you to in-network providers.
  • Supplement plans have predictable costs (premium plus standard Medicare costs) but higher monthly premiums; Advantage plans often have lower or zero premiums but charge copays and coinsurance for each visit.
  • Supplement plans cover you anywhere in the United States; Advantage plans usually do not cover care outside their service area except emergencies.
  • You can switch between Supplement and Advantage plans during Open Enrollment (October 15 to December 7 each year) or during certain life events.
  • Supplement plans are standardized by the federal government, so Plan G from one insurer covers the same things as Plan G from another; Advantage plans vary widely by insurer and region.

How costs work: premiums, deductibles, and out-of-pocket limits

With a Supplement plan, you pay three things: your Medicare Part B premium (set by Medicare), your Supplement premium (set by the insurance company), and your share of Medicare costs (copayments and coinsurance). Once you meet Medicare's deductible, the Supplement plan typically covers the rest. Your total out-of-pocket cost is predictable month to month.

With an Advantage plan, you pay your Medicare Part B premium plus the Advantage plan's premium (often $0 to $50 per month). Then you pay copays or coinsurance when you use care — usually $10 to $50 per doctor visit, more for specialists or hospital stays. Advantage plans have an out-of-pocket maximum (the most you will pay in a year), which varies by plan but often ranges from $5,000 to $7,000. Once you hit that limit, the plan covers 100 percent of covered services for the rest of the year.

Supplement premiums are typically higher than Advantage premiums — sometimes $100 to $300 per month — but you know exactly what you will pay. Advantage premiums are lower, but your actual costs depend on how much care you use. If you see doctors frequently or have chronic conditions, Advantage copays can add up quickly.

Network restrictions and where you can receive care

Supplement plans have no network. Any doctor, hospital, or specialist that accepts Medicare will accept your Supplement plan. You can travel across the country and see care anywhere. This freedom is one of the biggest reasons people choose Supplement plans.

Advantage plans have networks. You must see doctors and hospitals in the plan's network, or pay much more (or the full cost yourself). Some Advantage plans are HMOs, which require you to pick a primary care doctor and get referrals to see specialists. Others are PPOs, which let you see specialists without a referral but still charge more if you go out of network. A few are regional plans that cover a specific area, so if you move or travel, you may not have coverage.

If you have a doctor you want to keep seeing, check whether they are in the Advantage plan's network before you sign up. If your doctor is not in the network and you want to keep seeing them, a Supplement plan is usually the better choice.

Coverage outside the United States

Supplement plans cover you when you travel outside the United States — a major advantage if you spend time abroad or have family overseas. Original Medicare does not cover foreign care, but your Supplement plan will pay its share of costs in most countries.

Advantage plans almost never cover care outside the United States, except in rare cases for emergency care in border areas. If you travel internationally or spend winters outside the country, a Supplement plan is the safer choice.

Standardized plans: what you are actually buying

The federal government standardizes Supplement plans. There are ten plans (labeled A through N), and each one covers the same set of benefits no matter which insurance company sells it. Plan G from Blue Cross covers exactly what Plan G from Aetna covers. This makes it straightforward to compare prices — you can call different companies and get quotes for the same plan.

Advantage plans are not standardized. Each insurance company designs its own plan, with its own network, copays, and extra benefits. Plan A from one company may be completely different from Plan A from another company. You have to read the details of each plan to know what you are getting.

When you can switch between plan types

You can change from a Supplement plan to an Advantage plan, or vice versa, during Open Enrollment, which runs from October 15 to December 7 each year. Changes take effect January 1.

You can also switch outside Open Enrollment if you have a may have access to life event — you move out of your plan's service area, you lose employer coverage, or you become may be able to access for Medicaid. Each situation has different rules about timing and which plans you can choose.

One important note: if you have a Supplement plan and switch to an Advantage plan, you may not be able to switch back to a Supplement plan later without answering health questions. Insurance companies can deny you or charge more based on your health history. If you think you might want to go back to a Supplement plan someday, talk to your current insurer about your options before you switch.

Extra benefits: dental, vision, and hearing

Supplement plans cover only what Original Medicare covers. They do not include dental, vision, or hearing benefits. If you need these services, you pay out of pocket or buy a separate plan.

Many Advantage plans include dental, vision, and hearing coverage — sometimes at no extra cost, sometimes for a small copay. The coverage is usually limited (for example, one cleaning per year, or a $200 allowance for glasses), but it can save money if you use these services regularly. Check the plan's details to see what is included.

Frequently Asked Questions

Can I have both a Supplement plan and an Advantage plan at the same time?

No. You can have either Original Medicare with a Supplement plan, or an Advantage plan. You cannot have both. If you enroll in an Advantage plan, your Supplement plan ends automatically. If you later switch back to Original Medicare, you will need to enroll in a new Supplement plan.

What happens to my Supplement plan if I move to a different state?

Your Supplement plan usually stays active, because Supplement plans have no network. However, some insurance companies do not sell Supplement plans in every state. Contact your insurer to confirm your plan is available in your new state. If it is not, you can switch to a different Supplement plan during your move, which counts as a may have access to event.

Do Advantage plans cover prescription drugs?

Most Advantage plans include prescription drug coverage (Part D). Supplement plans do not. If you have a Supplement plan, you must enroll in a separate Part D plan to cover medications. You can change your Part D plan every year during Open Enrollment, even if you do not change your Supplement plan.

Which plan type is cheaper?

It depends on your health and how much care you use. Advantage plans have lower premiums but higher per-visit costs, so they cost less if you are healthy and see doctors rarely. Supplement plans have higher premiums but lower per-visit costs, so they cost less if you see doctors frequently or have ongoing health needs. Calculate your expected costs for both types before you decide.

Can I switch from Advantage to Supplement if I am unhappy with my network?

Yes, during Open Enrollment (October 15 to December 7). However, when you switch to a Supplement plan, the insurance company can ask health questions and may deny you or charge more based on your answers. Some states have protections that let you switch without health questions if you are switching away from an Advantage plan for the first time, but rules vary. Contact your state's health insurance counselor (through your Area Agency on Aging) to learn what protections explore to you.