The Core Difference Between Medigap and Medicare Advantage
Medigap and Medicare Advantage are two different ways to cover costs that Original Medicare (Part A and Part B) does not pay. They work in opposite directions. Medigap is supplemental insurance sold by private companies that pays some of the bills Medicare leaves behind — copays, coinsurance, deductibles. Medicare Advantage is an alternative to Original Medicare altogether; it is a single plan from a private insurer that includes hospital, doctor, and usually prescription drug coverage, all bundled together.
The choice between them shapes how you see doctors, what you pay, and which insurance company handles your claims. Most people must pick one or the other, not both. Understanding how each one works will help you decide which fits your situation and budget.
Key Takeaways
- Medigap supplements Original Medicare by covering costs Medicare does not pay, while Medicare Advantage replaces Original Medicare with a single private plan.
- With Medigap, you keep your Medicare card and see any doctor who accepts Medicare; with Medicare Advantage, you usually must use in-network doctors or pay more.
- Medigap premiums are predictable and do not change based on health, but Medicare Advantage premiums are often lower and may include dental or vision coverage.
- Medicare Advantage plans have annual out-of-pocket limits; Medigap plans do not, though Medigap premiums can be higher overall.
- You can switch between Medigap and Medicare Advantage during Open Enrollment in the fall, but switching away from Medigap later may mean paying higher premiums.
How Medigap Works and What It Covers
When you have Original Medicare (Part A and Part B) plus a Medigap policy, you are covered by two insurance companies working in sequence. You see a doctor, Medicare pays its share, and then Medigap pays some or all of what Medicare did not cover. You submit one claim, and the providers handle the coordination between the two insurers.
Medigap comes in ten standardized plans labeled A through N. Each plan covers a different combination of costs. Plan A is the most basic and least expensive; Plan G and Plan N are more comprehensive. All Plan G policies, for example, cover the same benefits no matter which company sells it — the difference is only in the monthly premium. This standardization makes it easier to compare prices across insurers.
With Medigap, you keep your Original Medicare benefits and can see any doctor or hospital in the United States that accepts Medicare. There are no networks, no referrals required, and no prior authorization for most services. You pay your Medigap premium monthly, separate from your Medicare Part B premium.
How Medicare Advantage Works and What It Covers
Medicare Advantage is a complete replacement for Original Medicare. Instead of having a Medicare card and a separate Medigap card, you have one Medicare Advantage card from a private insurer like UnitedHealthcare, Humana, or Anthem. That single plan covers hospital care (Part A), doctor visits (Part B), and usually prescription drugs (Part D) all in one.
Most Medicare Advantage plans are Health Maintenance Organizations (HMOs) or Preferred Provider Organizations (PPOs). HMO plans require you to use in-network doctors and usually require a referral to see a specialist. PPO plans let you see out-of-network doctors but charge you more. Some plans also include dental, vision, hearing, or fitness benefits that Original Medicare does not cover.
Medicare Advantage plans have an annual out-of-pocket maximum — a cap on what you will pay in copays and coinsurance in a given year. Once you reach that limit, the plan pays 100 percent of covered services for the rest of the year. Original Medicare has no such cap, which is one reason people choose Medigap.
Comparing Costs: Premiums, Deductibles, and Out-of-Pocket Limits
The cost picture differs sharply between the two. Medicare Advantage premiums are often lower — sometimes zero — because the plans receive a fixed payment from Medicare for each member. However, you pay copays and coinsurance when you use services, and those costs add up if you see doctors frequently. The trade-off is that your total spending is capped by the annual out-of-pocket maximum.
Medigap premiums are higher on average, but once you pay them, most of your other costs disappear. Many Medigap plans cover the Part B deductible and charge zero copay for doctor visits. You are paying more upfront but less when you actually need care. Medigap premiums can increase with age or when you renew, and they vary by location and insurer — there is no standardized price.
The table below shows how costs typically flow for each plan type:
| Cost Type | Medigap | Medicare Advantage |
|---|---|---|
| Monthly Premium | Higher (varies by plan and insurer) | Often lower or zero |
| Doctor Visit Copay | Usually zero | $10–$50 per visit |
| Hospital Deductible | Usually covered | $0–$500 per stay |
| Annual Out-of-Pocket Cap | None | $7,550 (2024) |
| Prescription Drugs | Separate Part D plan required | Usually included |
Network Restrictions and Doctor Choice
If you have a doctor you want to keep seeing, network restrictions matter. With Medigap, you have no network. Your doctor accepts Medicare, you see them. You can travel and see any Medicare-accepting provider anywhere in the country without asking permission or paying extra.
Medicare Advantage plans restrict where you can go. HMO plans require you to use in-network doctors and hospitals, except in emergencies. If your current doctor is not in the plan's network, you must either switch doctors or pay the full cost of the visit out of pocket. PPO plans are more flexible — you can see out-of-network doctors — but you will pay higher copays or coinsurance. Before choosing a Medicare Advantage plan, check whether your doctors and preferred hospital are in the network.
When You Can Switch and What It Costs
You have the most flexibility during Open Enrollment, which runs from October 15 to December 7 each year. During this window, you can switch from Medigap to Medicare Advantage, from Medicare Advantage to Medigap, or between different plans of the same type. Changes take effect January 1.
If you have Original Medicare and want to buy Medigap for the first time, you have a six-month window after you turn 65 and enroll in Part B. During this period, insurers cannot deny you coverage or charge more based on health problems — this is called may provide issue. If you wait past this window, insurers can refuse to sell you a Medigap plan or charge you higher premiums because of pre-existing conditions.
Switching from Medicare Advantage back to Medigap later in life is possible but costly. You lose may provide issue protection, so insurers can underwrite your health and charge you more or deny you coverage entirely. For this reason, many people who choose Medigap early stay with it.
Prescription Drug Coverage
Prescription drug coverage works differently under each plan type. If you have Original Medicare and Medigap, you must enroll in a separate Part D prescription drug plan sold by a private insurer. You pay a monthly premium for Part D on top of your Medicare and Medigap premiums. You choose which Part D plan to use based on which drugs you take and which pharmacies you prefer.
Medicare Advantage plans almost always include prescription drug coverage as part of the plan. You do not buy a separate Part D policy. The plan tells you which drugs are covered, what your copays are, and which pharmacies you can use. This bundling simplifies things but gives you less flexibility to shop for the best drug plan separately.
Frequently Asked Questions
Can I have both Medigap and Medicare Advantage at the same time?
No. Medicare rules prohibit holding both simultaneously. You must choose one or the other. If you enroll in Medicare Advantage while you have Medigap, your Medigap policy will be cancelled. Conversely, if you enroll in Medigap while you have Medicare Advantage, your Medicare Advantage plan ends.
Which plan is better for someone who sees doctors frequently?
Medigap is usually better if you see many doctors or specialists. Once you pay the monthly premium, most copays and deductibles are covered, so each visit costs little or nothing. Medicare Advantage can work too if you stay in-network, but copays add up quickly with frequent visits. Compare the annual out-of-pocket maximum against your expected costs.
What happens to my coverage if I travel outside the United States?
Medigap covers emergency care outside the US, and some plans cover routine care abroad. Medicare Advantage typically does not cover care outside the US except emergencies. If you travel internationally often, Medigap is the safer choice.
Do I need to choose between these plans when I first turn 65?
You do not have to choose when ready, but waiting past your Initial Enrollment Period can cost you. If you delay enrolling in Part B, you may face late-enrollment penalties. If you delay buying Medigap past six months after Part B enrollment, you lose may provide issue and may pay higher premiums or be denied coverage.
Can my Medicare Advantage plan change the network or drop my doctor mid-year?
Yes. Plans can change networks, drop doctors, or change copays at the start of each calendar year. If your doctor leaves the network mid-year, you usually have the right to continue seeing them through the end of the year at in-network rates. Check your plan documents or call the plan to understand your options if this happens.