The core difference: how each plan pays your medical bills
Medicare Advantage and Medigap are two different ways to get coverage beyond Original Medicare. They work in opposite directions, and which one costs less depends entirely on how much medical care you use.
Medicare Advantage is an all-in-one plan run by a private insurance company. It includes hospital, doctor, and prescription drug coverage in one policy. You pay a monthly premium, a deductible, and copays when you see a doctor. The trade-off: you must use doctors and hospitals in the plan's network, except in emergencies.
Medigap is a supplement sold by a private insurance company that works alongside Original Medicare. You keep your Original Medicare coverage and add a Medigap policy on top. Medicare pays its share of your bill first, then Medigap pays its share. You can see any doctor or hospital that accepts Medicare, which is nearly all of them.
The choice between them hinges on three things: how much you go to the doctor, whether you have a preferred doctor or hospital, and what you can afford to pay upfront each month.
Key Takeaways
- Medicare Advantage limits you to in-network doctors and hospitals but often has lower monthly premiums; Medigap lets you see any Medicare provider but costs more per month.
- Medicare Advantage includes prescription drug coverage automatically; with Medigap you must buy a separate Part D plan.
- Medicare Advantage has yearly out-of-pocket limits that cap your total costs; Medigap does not, so costs can grow if you need a lot of care.
- You can switch between Medicare Advantage and Medigap only during specific enrollment periods, usually once a year.
- If you have a chronic condition and see the same doctors regularly, Medigap may cost less overall; if you rarely see a doctor, Medicare Advantage may be cheaper.
Medicare Advantage: lower premiums, limited network, built-in drug coverage
Medicare Advantage plans often have a $0 monthly premium, which is why many people choose them. But that low premium comes with strings. You must use doctors and hospitals in the plan's network. If you see an out-of-network doctor without a referral, you pay the full bill yourself—or the plan pays nothing.
Every Medicare Advantage plan includes prescription drug coverage (Part D) as part of the package. You do not buy it separately. The plan also sets a yearly out-of-pocket maximum—a cap on what you pay in copays and deductibles combined. Once you hit that limit, the plan covers the rest of your care for the year. This ceiling protects you if you have a serious illness or injury.
Medicare Advantage plans often add benefits Original Medicare does not cover: dental, vision, hearing, or fitness programs. These extras can be valuable if you use them, but they vary widely by plan and by region.
The catch: if you travel or move, your plan may not work in another state. If your doctor leaves the network, you may have to switch doctors mid-year. And if you need a specialist, many plans require you to get a referral from your primary care doctor first.
Medigap: higher premiums, full provider choice, no drug coverage included
Medigap plans cost more per month than Medicare Advantage, sometimes $150 to $300 or more depending on your age and location. But you get something in return: you can see any doctor or hospital in the United States that accepts Medicare. No referrals, no networks, no surprise bills from out-of-network care.
Medigap comes in lettered plans (A, B, D, G, K, L, M, N). Each letter covers a different set of costs. Plan G, for example, covers your Part B deductible, coinsurance, and copays. Plan N covers most of the same things but charges you a small copay at the doctor's office. The letter you choose determines what you pay out of pocket.
Medigap does not include prescription drug coverage. You must buy a separate Part D plan, which adds another $10 to $100 per month depending on the drugs you take. This is a separate enrollment and a separate monthly bill.
Medigap has no yearly out-of-pocket limit. If you need a lot of medical care, your costs can keep climbing. But because Medigap covers most of your copays and coinsurance, your actual bills tend to be predictable and low.
Cost comparison: when each plan saves you money
The total cost of each plan depends on your health and how often you see a doctor. There is no universal answer.
Medicare Advantage costs less if: You are generally healthy and see a doctor only once or twice a year. Your monthly premium is low or zero, and your copays stay small because you do not hit them often. You do not take many prescription drugs. You live in an area with a large network of doctors and hospitals you like.
Medigap costs less if: You have a chronic condition like diabetes or heart disease and see multiple doctors regularly. You take several prescription drugs. You want to keep seeing the same doctors without worrying about network changes. You travel frequently or split time between states. You are willing to pay more per month for predictable, lower out-of-pocket costs.
To compare actual costs, gather your recent medical bills and prescription list. Call a few Medicare Advantage plans in your area and ask what your copays would be for your doctors and drugs. Then get quotes for Medigap plans and a Part D plan. Add up the premiums, copays, and deductibles for a full year. The plan with the lowest total is usually the better choice for you.
Network and provider choice: the biggest practical difference
If you have a doctor you trust and want to keep seeing them, check whether they are in the Medicare Advantage plan's network before you enroll. Call the doctor's office directly—do not rely on the plan's website, which can be out of date. Ask if they are accepting new Medicare Advantage patients from that specific plan.
With Medigap, your doctor choice is almost unlimited. Any doctor who accepts Medicare accepts Medigap. This matters most if you have a specialist you depend on, or if you live in a rural area where only one or two doctors practice.
Medicare Advantage plans can change their networks every year. A doctor you see in January might leave the network by March. Medigap does not have this problem—your coverage stays the same regardless of which doctors are in or out of network.
Switching between plans: timing and rules
You cannot switch from Medicare Advantage to Medigap whenever you want. There are specific windows when you can make the change.
If you are new to Medicare (turning 65 or becoming may be able to access), you have a 6-month window to buy any Medigap plan without the insurance company asking about your health history. This is called the Medigap open enrollment period. If you miss this window and try to buy Medigap later, the company can deny you or charge you more if you have a pre-existing condition.
If you are already on Medicare Advantage and want to switch to Medigap after your open enrollment period has ended, the insurance company can reject you or charge higher premiums based on your health. Some states have protections that limit this, but not all.
You can switch between different Medicare Advantage plans, or from Medigap to a different Medigap plan, during the Annual Enrollment Period (October 15 to December 7 each year). Changes take effect January 1.
Prescription drugs: coverage differences that matter
Medicare Advantage includes Part D prescription drug coverage in the plan. The copays and coverage rules are set by that plan. If your drug is not on the plan's formulary (the list of covered drugs), you may have to pay the full price or switch to a different drug.
With Medigap, you buy Part D separately from any insurance company offering it in your area. You can choose a plan based on which drugs you take, not based on your Medigap plan. If your drug costs too much under one Part D plan, you can switch to a different Part D plan during the Annual Enrollment Period.
Both Medicare Advantage and Medigap users pay the same Part D premiums and follow the same coverage rules set by Medicare. The difference is flexibility: Medigap users can shop for the Part D plan that works best for their specific drugs.
Frequently Asked Questions
Can I switch from Medicare Advantage to Medigap if I already missed the open enrollment period?
You can try, but the insurance company can reject you or charge you more based on your health history. Some states require companies to accept you anyway, but this varies. Your best option is to wait for the Annual Enrollment Period (October 15 to December 7) and switch then, or talk to your State Health Insurance information Program (SHIP) office about your state's rules.
What happens if my Medicare Advantage doctor leaves the network?
You can see them as an out-of-network provider and pay out-of-network copays, which are usually higher. Or you can switch to a different doctor in the network. If your doctor leaves during the year, you may be able to switch to a different Medicare Advantage plan outside the normal enrollment period—ask your plan.
Do I have to take prescription drugs to choose Medicare Advantage?
No. If you do not take any prescription drugs, you still get Part D coverage included in your Medicare Advantage plan. You do not have to use it, but it is there if you need it later. With Medigap, you can also skip Part D if you do not take drugs, but you should enroll in Part D within three months of becoming may be able to access, or you may pay a penalty later.
Which plan is better for someone with multiple chronic conditions?
Usually Medigap, because you can see any doctor without worrying about networks or referrals, and your out-of-pocket costs are more predictable. But run the numbers for your specific situation: add up the Medigap premium, Part D premium, and expected copays, then compare it to the Medicare Advantage premium and copays. The answer depends on your doctors and drugs.
Can I have both Medicare Advantage and Medigap at the same time?
No. Medicare does not allow it. You must choose one or the other. If you enroll in Medicare Advantage, you automatically lose any Medigap coverage you had, and vice versa.