Whether you need supplemental insurance with Medicare depends on your coverage gaps and how much out-of-pocket costs you can handle

Medicare covers a lot, but not everything. You will still pay deductibles, copayments, and coinsurance for the services it does cover. You will also pay the full cost of services it does not cover at all — like routine dental, vision, or hearing care. Supplemental insurance (also called Medigap) and Medicare Advantage are the two main ways people fill those gaps. Neither is required by law, but both can protect you from large medical bills.

The choice between them — or choosing neither — depends on which gaps matter most to you, which doctors you want to see, and what you can afford to pay in premiums. This guide explains what each covers and how to think through the decision.

Key Takeaways

  • Supplemental insurance (Medigap) works alongside Original Medicare and covers some of the costs Medicare does not, like copayments and coinsurance.
  • Medicare Advantage is an alternative to Original Medicare that often includes dental, vision, and hearing, but limits you to in-network doctors and requires prior approval for some services.
  • You do not need supplemental insurance if you choose Medicare Advantage, because the two cannot be used together.
  • If you stay on Original Medicare without supplemental coverage, you pay the full cost of services Medicare does not cover and all copayments and deductibles out of pocket.
  • The best time to buy Medigap is within six months of turning 65 or enrolling in Medicare Part B, because prices are lower and insurers cannot deny you based on pre-existing conditions.

What Medigap (Supplemental Insurance) Actually Covers

Medigap policies are sold by private insurance companies and are designed to pay the costs that Original Medicare leaves behind. These include your share of the bill after Medicare pays its part — the copayments, coinsurance, and deductibles. Different Medigap plans (labeled A through N) cover different combinations of these costs.

For example, Plan G covers your Part B deductible, copayments for hospital stays, and coinsurance for skilled nursing facilities. Plan N covers similar items but charges you a copayment when you see a doctor. The trade-off is that Plan N costs less in premiums but more per visit. Medigap does not cover dental, vision, hearing, or long-term care — those gaps remain even with supplemental insurance.

Medigap premiums vary by age, location, and the plan you choose. You pay the premium to the insurance company, then continue paying Medicare premiums as well. You can use any doctor or hospital that accepts Medicare, which gives you more freedom than Medicare Advantage.

How Medicare Advantage Differs From Supplemental Insurance

Medicare Advantage (Part C) is a different path entirely. Instead of Original Medicare plus Medigap, you enroll in a plan run by a private insurance company that contracts with Medicare. The insurance company becomes your primary coverage for hospital, doctor, and prescription drug services.

Most Medicare Advantage plans include dental, vision, and hearing coverage — benefits that Medigap does not offer. Many also include fitness programs or other wellness services. Premiums are often lower than Original Medicare plus Medigap combined. The catch is that you must use doctors and hospitals in the plan's network (except in emergencies), and many services require prior approval from the insurance company before you receive them.

You cannot have both Medigap and Medicare Advantage at the same time. If you enroll in Medicare Advantage, you do not need supplemental insurance because the plan is designed to be your complete coverage.

When You Might Not Need Supplemental Insurance

You do not need Medigap if you choose Medicare Advantage instead. You also do not need it if you can afford to pay copayments, coinsurance, and deductibles out of pocket and you do not mind paying the full cost of services Medicare does not cover.

Some people stay on Original Medicare alone because they have other insurance through a current or former employer, a union, or TRICARE (military coverage). That other insurance may cover the gaps that Medigap would. Before you decide to skip supplemental coverage, confirm with your other insurer that they will coordinate with Medicare and cover the specific costs you are worried about.

If you have limited income and cannot afford Medigap premiums, you may be able to get help through your state's Medicare Savings Program, which pays some or all of your Medicare premiums and cost-sharing. This is different from Medigap but serves a similar purpose.

When Supplemental Insurance Makes Financial Sense

Medigap is worth the premium cost if you see doctors frequently, take multiple medications, or have a chronic condition. The copayments and coinsurance add up quickly, and Medigap caps your out-of-pocket costs. If you have a plan that covers coinsurance (like Plan G), you know exactly what you will pay for a hospital stay or surgery — the insurance company pays the rest.

Medigap also gives you access to any doctor or hospital that accepts Medicare, which matters if you have a specialist you want to keep seeing or if you travel and want to see doctors in different states without worrying about networks.

The premium you pay for Medigap is predictable and does not change based on how much care you use. If you use very little medical care, you may pay more in premiums than you save in copayments. But if you use moderate to high amounts of care, the premium usually pays for itself.

The Enrollment Window and When Prices Lock In

The best time to buy Medigap is within six months of turning 65 or enrolling in Medicare Part B. During this window, called the Medigap Open Enrollment Period, insurance companies must sell you any plan they offer at the lowest available price, and they cannot deny you or charge more based on pre-existing conditions.

If you miss this window, you can still buy Medigap later, but the insurer can charge you more based on your health history, and they can refuse to sell you a plan altogether. Some states have additional protections that extend this window or allow you to switch plans later, but the rules vary. The safest approach is to enroll during the six-month window.

If you are already on Medicare Advantage and want to switch to Original Medicare plus Medigap, you have a limited window to do so without facing higher premiums or denial. This window is usually 12 months from when you first enrolled in Medicare Advantage, though some states offer longer periods.

How to Compare Your Options

Start by listing what matters most to you: Do you want to see any doctor, or are you comfortable with a network? Do you need dental, vision, or hearing coverage? How often do you see a doctor? How much can you afford to pay in premiums each month?

If you want maximum choice of doctors and predictable costs, Original Medicare plus Medigap is usually the answer. If you want lower premiums and coverage for dental and vision, Medicare Advantage may be better — but only if you are comfortable with networks and prior approval requirements.

Get quotes for Medigap plans in your area and compare them to Medicare Advantage plans available to you. The Medicare.gov Plan Finder tool lets you enter your zip code and see both options side by side, including premiums, deductibles, and what each covers. You can also call 1-800-MEDICARE to speak with someone who can walk you through the comparison.

Frequently Asked Questions

Can I switch from Medicare Advantage to Medigap later?

Yes, but only during certain windows. If you are still within 12 months of first enrolling in Medicare Advantage, you can switch to Original Medicare and buy Medigap without the insurer charging you more based on your health. After that window closes, you may face higher premiums or denial. Some states have longer windows — check with your state's insurance commissioner's office.

Do I have to buy Medigap from the same company that sells my Medicare Advantage plan?

No. Medigap is sold by private insurance companies, and you can buy from any company licensed to sell it in your state. You are not locked into one insurer. You can shop around and compare prices and coverage.

What if I have both Medicare and Medicaid?

If you may have access to for both (called "dual may be able to access"), Medicaid may cover some costs that Medicare does not, including long-term care. You may not need Medigap because Medicaid fills some of those gaps. Contact your state Medicaid office to understand what your coverage includes before buying supplemental insurance.

Does Medigap cover prescription drugs?

No. Medigap covers cost-sharing for services Medicare covers, but not prescription drugs. You need to enroll in Medicare Part D (prescription drug coverage) separately. Part D is sold by private insurers and covers medications on a formulary list.

What happens to my Medigap coverage if I move to a different state?

Your Medigap policy ends when you move. You will need to buy a new policy from an insurer in your new state. If you move within the first six months of turning 65 or enrolling in Medicare Part B, you may still be in your Medigap Open Enrollment Period and can buy a new plan without higher premiums based on health. After that window, you may face higher costs.