Medicare Advantage and Medicare Supplement (also called Medigap) take fundamentally different approaches to your healthcare coverage. Medicare Advantage replaces Original Medicare with a private plan that bundles your benefits together. Medicare Supplement works alongside Original Medicare, filling in the gaps like deductibles and coinsurance that Original Medicare leaves you to pay. That single distinction drives every other difference between the two, from what doctors you can see to what you’ll pay each month.
How Each Plan Actually Works
With Original Medicare alone, you’re responsible for roughly 20% of most medical costs after meeting your deductible, and there’s no cap on how much you could spend in a year. Both Medicare Advantage and Medigap exist to solve that problem, but they do it in opposite ways.
A Medicare Supplement policy is a layer on top of Original Medicare. Medicare processes your claims first, and then your Medigap policy picks up some or all of whatever Medicare didn’t cover. You still have Original Medicare as your primary insurance. A Medicare Advantage plan, on the other hand, is a completely separate insurance product run by a private company. When you enroll, you leave Original Medicare behind (even though you still technically have Parts A and B). The private plan takes over responsibility for delivering all your Medicare benefits, often with its own rules about copays, networks, and prior authorization.
Doctor Choice and Provider Networks
This is where the two options diverge most sharply in daily life. Original Medicare lets you see any doctor or hospital that accepts Medicare, anywhere in the country, including Puerto Rico, the U.S. Virgin Islands, and other territories. Since Medigap simply supplements Original Medicare, it follows those same rules. You don’t need referrals to see specialists, and you can get care in any state without worrying about network restrictions.
Medicare Advantage plans typically require you to use doctors and hospitals within the plan’s network for non-emergency care. Many plans use HMO structures that require a referral from your primary care doctor before you can see a specialist. PPO-style Advantage plans give you more flexibility to go out of network, but you’ll pay significantly more when you do. Advantage plans also operate within a defined service area, usually limited to a specific region or state. If you spend winters in Arizona and summers in Michigan, this is worth paying close attention to.
What Each Option Costs
The cost structures feel almost like mirror images. Medigap plans charge a noticeable monthly premium but dramatically reduce what you pay when you actually need care. The average monthly premium for Plan G, the most popular Medigap policy, was $164 in 2023, though it ranged from about $140 in some states to $236 in New York. On top of that, you still pay your Part B premium. In exchange, your out-of-pocket costs at the doctor or hospital drop to near zero for most covered services.
Medicare Advantage plans often advertise $0 monthly premiums, which is genuinely common. But the tradeoff is higher cost-sharing when you use care: copays for doctor visits, coinsurance for procedures, and deductibles for certain services. The federal government sets a maximum out-of-pocket limit for Advantage plans at $9,350 for in-network services in 2025, though the average plan actually caps spending at around $5,320 for in-network care. Plans that include out-of-network coverage can have combined limits up to $14,000. If you’re generally healthy and use little care, Advantage’s lower premiums save money. If you have frequent medical needs, Medigap’s higher premium can protect you from large bills.
Prescription Drug Coverage
Most Medicare Advantage plans bundle prescription drug coverage (Part D) directly into the plan. You get medical and pharmacy benefits in a single package. Medigap policies sold after 2005 do not include prescription drug coverage at all. If you choose Medigap, you need to enroll in a separate standalone Part D plan and pay an additional premium for it.
Starting in 2025, all Part D plans, whether standalone or embedded in an Advantage plan, include a $2,000 annual cap on out-of-pocket drug spending. Once you hit that threshold, you pay nothing for covered prescriptions for the rest of the year. This applies equally to both paths, so the drug cost difference between Advantage and Medigap has narrowed considerably.
Dental, Vision, and Hearing Benefits
This is one of Medicare Advantage’s biggest selling points. Original Medicare generally does not cover routine dental, hearing, or vision services, which means Medigap doesn’t cover them either. Medicare Advantage plans frequently do. In 2021, 94% of Advantage enrollees had access to some dental coverage, 97% had hearing benefits, and 99% had some vision coverage.
The depth of that coverage varies. Most enrollees with dental benefits get both preventive and more extensive services like fillings and root canals, but plans commonly impose annual dollar limits averaging around $1,300. Coinsurance for major dental work is typically 50%, so you’re still paying a meaningful share. Hearing benefits usually cover both exams and hearing aids, with an average dollar cap of about $960 per year. Vision coverage almost always includes eye exams and eyewear, but the average annual limit for eyewear is just $160. These extras are real, but they’re not as generous as they might sound at first glance.
If you choose Medigap, you’d need to buy separate dental, vision, and hearing coverage on your own, or pay out of pocket.
Travel and Out-of-State Coverage
If you travel frequently, this difference matters. Medigap paired with Original Medicare works anywhere in the country that accepts Medicare. Most Medigap plans (including the popular Plans G and N) also cover foreign travel emergencies, paying 80% of emergency care costs abroad after a $250 annual deductible, with a $50,000 lifetime limit. Coverage applies during the first 60 days of any trip.
Medicare Advantage plans are generally limited to their local service area for routine care. Emergency care is covered anywhere, but non-emergency visits outside your plan’s network or region can be expensive or not covered at all. If you regularly travel internationally or split time between states, Medigap offers considerably more flexibility.
Enrollment Timing and Switching
When you can enroll, and how easily you can switch, is one of the most important practical differences. Medicare Advantage has an annual enrollment period every fall (October 15 through December 7), and you can switch plans each year without any health screening. If a plan changes its network or raises costs, you can move to a different one.
Medigap works differently. Your best window is the six-month Medigap Open Enrollment Period, which starts the first day of the month you turn 65 and are enrolled in Part B. During those six months, insurance companies must sell you any Medigap policy they offer at the standard price, regardless of your health. After that window closes, there’s no federal guarantee that a company will sell you a policy at all. If they do, they can charge more based on your health history. This makes the initial decision especially consequential: choosing Medicare Advantage at 65 and trying to switch to Medigap years later can be difficult or prohibitively expensive if you’ve developed health conditions.
Some states have their own protections that extend Medigap access beyond the federal rules, and there are limited “guaranteed issue” situations where you can buy Medigap outside the open enrollment window, such as when an Advantage plan leaves your area. But in general, switching from Advantage to Medigap later in life is far more restricted than the reverse.
Which Option Fits Your Situation
The right choice depends on your health, your budget, and how you use healthcare. Medigap paired with Original Medicare and a standalone Part D plan gives you the widest access to doctors, the most predictable costs, and the best travel coverage. The tradeoff is higher monthly premiums and no built-in dental, vision, or hearing benefits.
Medicare Advantage keeps monthly costs low, bundles drug coverage and extra benefits into one plan, and caps your annual spending. The tradeoff is a restricted provider network, potential referral requirements, and less flexibility if you move or travel. Healthy people in a stable location with good local Advantage plan options often do well with Medicare Advantage. People with chronic conditions, those who see multiple specialists, or those who want to see any doctor in the country tend to prefer Medigap’s broader access and lower cost-sharing at the point of care.