What Supplemental Insurance Does and Doesn't Cover

Medicare supplemental insurance, also called Medigap, pays some of the costs that Original Medicare leaves you responsible for — copayments, coinsurance, and deductibles. It does not cover services Medicare itself does not cover, like dental, vision, or hearing aids. It also does not replace Medicare; you keep your Medicare card and use both together.

Original Medicare covers hospital stays (Part A) and doctor visits (Part B), but it leaves gaps. For example, Medicare Part B has a yearly deductible you pay before coverage starts, and then you pay 20 percent of the cost of most services for the rest of the year. A Medigap plan picks up some or all of those costs, depending on which plan you choose.

The trade-off is straightforward: you pay a monthly premium to the insurance company selling the Medigap plan, and in return they cover the gaps. Whether that trade-off makes sense depends on how much medical care you use, what you can afford to pay out of pocket, and whether you prefer predictable costs or lower premiums.

Key Takeaways

  • Medigap covers copayments and deductibles that Original Medicare does not, but you must have Original Medicare to buy it — it does not work with Medicare Advantage.
  • Ten standardized Medigap plans exist (labeled A through N), and the same plan letter covers the same benefits no matter which insurance company sells it.
  • You have a six-month open enrollment window starting the month you turn 65 and sign up for Medicare Part B; during this window, insurers cannot deny you or charge more based on health history.
  • If you miss open enrollment and wait to buy Medigap later, insurers can charge you more or refuse to sell you a plan, depending on your state.
  • The decision between Medigap and Medicare Advantage hinges on whether you want predictable out-of-pocket costs and freedom to see any doctor, or lower premiums and integrated drug coverage.

The Ten Medigap Plans and What Each Covers

Insurance companies can only sell you one of ten standardized plans, labeled A through N. Plan A is the most basic; Plan G and Plan N are the most common choices for people enrolling now. The standardization means that Plan G from one company covers exactly the same benefits as Plan G from another — the only difference is the monthly premium.

Plan G covers the Part B deductible, copayments for doctor visits, coinsurance for hospital stays, and skilled nursing facility coinsurance. Plan N is similar but does not cover the Part B deductible, and it charges you a copayment for some doctor visits and emergency room visits. Plan A is cheaper but covers fewer costs. Plans F and C are no longer sold to people new to Medicare, though people who had them before 2020 can keep them.

You do not choose which plan is "best" — you choose which one fits your budget and your tolerance for out-of-pocket costs. If you want the lowest possible copayments and coinsurance, Plan G costs more per month but covers more. If you want the lowest premium, Plan A or Plan N costs less per month but leaves you paying more when you see a doctor or go to the hospital.

When You Can Buy Medigap Without Penalty

The critical window is your Medigap open enrollment period, which runs for six months starting the first day of the month you turn 65 and sign up for Medicare Part B. During this window, any insurance company must sell you any Medigap plan you want at the standard rate for your age. They cannot refuse you, charge you more, or exclude coverage for pre-existing conditions.

If you miss this window, the rules change. Some states have protections that let you buy Medigap later without penalty, but most do not. In most states, if you wait to buy Medigap after open enrollment ends, insurers can charge you more based on your health history, or refuse to sell you a plan at all. The penalty can be permanent — you may pay extra for the rest of your life.

The safest approach is to sign up for Medicare Part B and choose a Medigap plan during your open enrollment window, even if you are still working or do not think you will use much medical care. You can always switch to a different Medigap plan later during the annual open enrollment period (October 15 to December 7), though switching may trigger underwriting if you have developed health problems.

Medigap Versus Medicare Advantage: The Core Difference

You cannot have both Medigap and Medicare Advantage at the same time. You must choose one path. Original Medicare plus Medigap gives you predictable costs and the freedom to see any doctor who accepts Medicare. Medicare Advantage (Part C) is an alternative to Original Medicare sold by private insurance companies; it usually has lower or zero premiums but includes a network of doctors, copayments for each visit, and an annual out-of-pocket maximum.

With Medigap, you pay a monthly premium and then most of your copayments and coinsurance are covered. You can see any Medicare-accepting doctor without prior approval. With Medicare Advantage, you pay a lower premium (sometimes zero) but you must use doctors in the plan's network, you may need prior approval for specialists or procedures, and you hit an out-of-pocket maximum each year after which the plan covers everything.

Neither is objectively better. Medigap makes sense if you want to see specific doctors, travel frequently, or prefer knowing your costs in advance. Medicare Advantage makes sense if you want the lowest premium, you are comfortable with a network, and you want drug coverage built in. The choice depends on your health, your doctors, and your budget.

How Much Medigap Costs and What Affects the Price

Medigap premiums vary widely by plan, by insurance company, by your age, and by where you live. Plan A might cost $100 to $150 per month; Plan G might cost $200 to $350 per month. These are rough ranges and will differ in your area. The insurance company's website or a broker can quote you the exact premium for your zip code and age.

Three pricing methods exist: community-rated (everyone in your area pays the same regardless of age), age-rated (your premium rises as you age), and issue-age-rated (your premium is based on your age when you buy the plan and stays locked in). Age-rated plans are usually cheapest at first but cost more as you get older. Issue-age-rated plans cost more upfront but do not increase as fast.

Your premium does not change if your health gets worse — Medigap is may provide renewable. But it can increase if the insurance company raises rates for everyone in your plan or area. You can switch to a different Medigap plan or a different company during the annual open enrollment period (October 15 to December 7) without underwriting, though switching may mean a higher or lower premium depending on the new plan.

Common Mistakes to Avoid When Buying Medigap

The biggest mistake is waiting to buy Medigap after your six-month open enrollment window closes. Once that window ends, you lose the protection against being denied or charged more based on health history. If you have a chronic condition by then, you may face a much higher premium or be unable to buy a plan at all.

A second mistake is confusing Medigap with Medicare Advantage. Some people buy Medicare Advantage thinking it is supplemental coverage, then discover they cannot see their regular doctor or must pay a copayment for every visit. If you want Medigap, you must have Original Medicare (Part A and Part B), not Medicare Advantage.

A third mistake is buying a plan with more coverage than you need just because it is available. Plan G covers more than Plan N, but it also costs more. If you rarely see a doctor, the extra coverage may not be worth the extra premium. Conversely, if you have frequent medical needs, a cheaper plan with higher copayments may cost you more in the long run.

How to Find and Compare Medigap Plans in Your Area

Start by visiting Medicare.gov and using their Medigap plan finder tool. Enter your zip code and the tool will show you which plans are sold in your area, which companies sell them, and the premium for each. You can compare plans side by side to see which benefits each covers.

You can also contact insurance companies directly or work with a broker who sells Medigap plans. Brokers do not charge you a fee — they are paid by the insurance company — and they can help you understand the differences between plans and answer questions about your specific situation. Some brokers specialize in Medicare and can walk you through the enrollment process.

Before you buy, confirm that the plan is sold in your state and that the insurance company is licensed to sell it where you live. Some companies sell Medigap in some states but not others. Also confirm that you have Original Medicare (Part A and Part B) before you explore for Medigap — you cannot buy Medigap without it.

What Happens If You Switch Plans or Insurers Later

You can switch to a different Medigap plan or a different insurance company during the annual open enrollment period (October 15 to December 7). During this window, you can move to any plan without underwriting, meaning the new company cannot deny you or charge you more based on health history.

Outside this window, switching may trigger medical underwriting. The new company can ask about your health history and can refuse to sell you a plan or charge you more if you have developed health problems. Some states have limited protections that allow switching without underwriting in certain situations, but these vary by state.

If you are unhappy with your current plan or company, the safest time to switch is during the annual open enrollment period. Mark October 15 on your calendar each year so you do not miss the important date.

Frequently Asked Questions

Can I have Medigap and Medicare Advantage at the same time?

No. You must choose one or the other. If you have Medicare Advantage and buy Medigap, Medicare will cancel your Medigap coverage. If you have Medigap and switch to Medicare Advantage, your Medigap coverage ends.

What if I do not sign up for Medigap during my open enrollment window?

You can still buy Medigap later, but insurers can charge you more or refuse to sell you a plan, depending on your state and health history. Some states have protections; most do not. The penalty can be permanent. It is safer to enroll during your six-month window even if you do not think you will use it.

Does Medigap cover prescription drugs?

No. Medigap covers copayments and coinsurance for services Medicare covers, but it does not cover drugs. You need a separate prescription drug plan (Part D) for that. You can have both Medigap and Part D at the same time.

Can my Medigap premium go up if my health gets worse?

Your premium cannot go up because your health gets worse — Medigap is may provide renewable. But your premium can increase if the insurance company raises rates for everyone in your plan or area. You can shop for a lower-cost plan during the annual open enrollment period.

What is the difference between Plan G and Plan N?

Plan G covers the Part B deductible and has no copayments for doctor visits. Plan N does not cover the Part B deductible and charges copayments for some doctor visits and emergency room visits. Plan G costs more per month but covers more. Plan N costs less per month but leaves you paying more when you see a doctor.