Medicare Advantage replaces how you receive your Part A and Part B benefits with a private plan that usually has a provider network, a yearly out-of-pocket limit, and often built-in drug coverage. Medigap is a separate policy that works alongside Original Medicare to help pay the costs Medicare leaves behind, and it lets you see any provider in the country that accepts Medicare. You cannot use both at the same time.
Side by side
| Original Medicare + Medigap + Part D | Medicare Advantage | |
|---|---|---|
| Who pays your claims | Original Medicare pays first. Medigap pays some or all of what is left. | A private plan approved by Medicare. |
| Doctors and hospitals | Any provider in the U.S. that accepts Medicare. | Usually a network. HMOs generally require in-network care and referrals. PPOs let you go out of network, often at higher cost. |
| Monthly cost | Part B premium, plus a Medigap premium, plus a Part D premium. | Part B premium, plus the plan's premium if it has one. |
| Costs when you get care | Depends on the Medigap plan. Some plans leave very little to pay. | Copays and coinsurance as you use care, up to a yearly out-of-pocket limit. |
| Yearly limit on what you pay | Original Medicare has none. Medigap fills that gap, depending on the plan. | Every plan must have one for covered Part A and Part B services. |
| Drug coverage | Separate Part D plan. | Usually included. |
| Prior authorization | Rare in Original Medicare. | Plans can require approval before some services. |
| Travel | Coverage follows you anywhere in the U.S. | Mostly local, except emergencies and urgent care. Rules vary by plan. |
| When you can change | Medigap health questions can apply after your first 6-month window. | Once a year during Annual Enrollment, and January to March during the Advantage Open Enrollment Period. |
How Medicare Advantage works
A Medicare Advantage plan, also called Part C, is a private plan that contracts with Medicare to provide your Part A and Part B benefits. You still have Medicare, and you still pay your Part B premium. The plan simply becomes the one that handles your coverage and pays your claims.
Most Advantage plans work with a network of doctors, medical groups, and hospitals. Many include Part D drug coverage. What a specific plan covers varies, and it can change from year to year.
The trade-off is structure. You may need referrals to see specialists, approval before certain procedures, and you will generally need to use the plan's network. In exchange, every plan has a yearly cap on what you pay for covered medical services.
How Medigap works
A Medicare Supplement policy, often called Medigap, is sold by private insurance companies to help pay the costs Original Medicare does not, like deductibles, coinsurance, and copayments. Medigap plans are standardized and identified by letters. A Plan G from one company has the same basic benefits as a Plan G from another. What differs is the price and the company.
With Original Medicare and Medigap, you can generally see any doctor or hospital in the country that accepts Medicare, without referrals. You add a separate Part D plan for prescriptions.
Two plans, C and F, cannot be sold to people who became eligible for Medicare on or after January 1, 2020.
Questions that usually decide it
- Do you want to keep specific doctors? If yes, check whether they are in a plan's network before anything else.
- How much care do you expect to use? Frequent specialist visits, ongoing treatment, or a planned surgery change the math.
- Do you travel or split your year between states? Coverage that follows you matters more than it seems.
- Which would you rather have: a lower premium or predictable bills? There is no wrong answer. It is a preference.
- Could you pass health questions if you wanted Medigap later? If that is uncertain, the timing of your first choice carries extra weight.
Why switching later can be harder
Medicare Advantage lets you switch plans every year. Medigap is different. Outside of your first 6-month Medigap window and certain protected situations, a Medigap company can ask about your health and decide whether to sell you a policy and at what price. In California, people who already have Medigap get a yearly birthday window to change to a policy with the same or fewer benefits. Moving from Advantage to Medigap does not get that same protection.
There is one important safety net. If you join a Medicare Advantage plan when you are first eligible at 65, or you drop a Medigap policy to try Advantage for the first time, you generally have a trial right: within the first 12 months, you can go back to Original Medicare and buy a Medigap policy without health questions.
A plain rule of thumb: the first choice you make at 65 is the easiest one to make. Take the time to get it right, and ask about the trial right before you sign anything.
Common questions
Can I have Medicare Advantage and Medigap at the same time?
No. A Medigap policy only works with Original Medicare. If you join a Medicare Advantage plan, a Medigap policy will not pay your Advantage plan's costs, and it is generally illegal for anyone to sell you one while you are in an Advantage plan unless you are switching back to Original Medicare.
Which is cheaper, Medicare Advantage or Medigap?
It depends on how much care you use. Medicare Advantage often has lower monthly premiums but you pay copays and coinsurance as you use care, up to the plan's yearly limit. Medigap usually has a higher monthly premium but more predictable costs when you get care. The right answer depends on your health, your doctors, and your budget.
Can I switch from Medicare Advantage to Medigap later?
You can return to Original Medicare during certain enrollment windows, but buying a Medigap policy later may require answering health questions, and a company can turn you down or charge more. There are exceptions, including a one-year trial right for people who join Medicare Advantage when first eligible. That is why the first choice matters.
Does Medigap include prescription drug coverage?
No. Medigap policies sold today do not include drug coverage. If you choose Original Medicare with Medigap, you add a separate Part D prescription drug plan.
Do Medicare Advantage plans include drug coverage?
Most do. Plans that include it are often called MAPD plans. Some Advantage plans do not include drug coverage, so check before you enroll.
Where these facts come from: Medicare.gov: compare Original Medicare and Medicare Advantage; Medicare.gov: Medigap basics; California Health Benefits Review Program analysis of Medigap enrollment rules, 2025. Rules and dollar amounts change. Page reviewed October 4, 2026.