What a Medicare Supplement Plan Does and Why You Need One

A Medicare Supplement plan (also called Medigap) pays some of the costs that Original Medicare leaves you responsible for — copayments, coinsurance, and deductibles. Original Medicare covers a lot, but not everything. When you go to the hospital or see a doctor, you still owe money out of your pocket. A supplement plan fills those gaps by paying what Medicare does not.

You buy a supplement plan from a private insurance company, not from Medicare. The plan works alongside your Original Medicare coverage — it does not replace it. You keep your Medicare card and use it the same way. The supplement plan straightforward pays the bills Medicare does not cover.

Not everyone needs a supplement. If you choose a Medicare Advantage plan instead of Original Medicare, you cannot buy a supplement plan — Advantage plans have their own copayments and out-of-pocket limits built in. But if you stay on Original Medicare, a supplement plan protects you from unexpected medical bills.

Key Takeaways

  • Medicare Supplement plans are standardized by the federal government, so Plan G from one company covers the same things as Plan G from another — the only difference is price.
  • The most common plans for people turning 65 today are Plan G and Plan N, because Plan F (which used to be the most popular) is no longer sold to new enrollees.
  • You have a may provide right to buy a supplement plan during your initial enrollment period when you first turn 65 and sign up for Medicare Part B — after that window closes, insurers can deny you or charge more based on your health.
  • Comparing plans means looking at three things: which plan type covers what you need, which insurance companies sell it in your area, and what each company charges for that plan.
  • Your costs change every year as premiums rise, so you should review your plan choice each fall during open enrollment and switch if a cheaper option becomes available.

The Standardized Plan Types and What Each One Covers

The federal government sets what each supplement plan type covers. There is no such thing as a "better" Plan G from one company versus another — they cover identical benefits. The only variation is the monthly premium you pay. This standardization makes comparing plans much simpler than it sounds: once you decide which plan letter fits your needs, you just shop for the lowest price.

Plan G is the most common choice for people new to Medicare now. It covers most of what Original Medicare does not — hospital copayments, doctor visit copayments, and coinsurance. The main thing Plan G does not cover is the Part B deductible (the amount you pay before Medicare starts covering doctor visits). In 2024, that deductible is $240 per year, though it changes annually.

Plan N is less expensive than Plan G because it covers less. With Plan N, you pay a copayment when you see a doctor (usually $20) and a copayment for emergency room visits (usually $50, waived if admitted). You also pay the Part B deductible yourself. For people who do not go to the doctor often, Plan N costs less per month and may save money overall.

Plan F used to be the most popular, but Medicare stopped selling it to people who turned 65 after January 1, 2020. If you were already on Plan F before that date, you can keep it. If you are new to Medicare, Plan F is not an option. Plans A, B, D, and others exist but are chosen less often; your insurance agent can explain them if one seems to fit your situation.

When You Can Buy a Supplement Plan Without Health Questions

Timing matters enormously. When you first turn 65 and sign up for Medicare Part B, you have a may provide issue period — usually six months — during which any insurance company must sell you any supplement plan at the standard rate. They cannot ask about your health, deny you, or charge you more because you have diabetes, heart disease, or any other condition. This is the easiest and cheapest time to buy.

This window starts the month you turn 65 and enroll in Part B. If you miss it, you lose this protection. After the may provide issue period ends, an insurance company can refuse to sell you a plan, or they can charge you a higher premium based on your medical history. Some states have additional protections, but they vary widely. The safest approach is to buy during your initial enrollment period.

If you are still working at 65 and have health insurance through your job, you may be able to delay enrolling in Medicare without penalty. When you do retire and enroll, you may still have a may provide issue period — the rules depend on your specific situation. Talk to Medicare or a counselor before you turn 65 if you think this applies to you.

How to Compare Plans and Find the Lowest Price

Start by deciding which plan type meets your needs. If you see doctors regularly or want the most predictable costs, Plan G covers more and may be worth the higher premium. If you are generally healthy and do not mind small copayments, Plan N costs less each month. Once you have picked a plan letter, the work becomes straightforward: find which companies sell that plan in your area and compare their prices.

Medicare.gov has a tool called the Medigap Plan Finder. Enter your zip code, select the plan type you want, and it shows you every insurance company selling that plan near you, along with their monthly premiums. Premiums vary significantly — sometimes by $50 or more per month for the identical coverage. The tool also shows customer service ratings and whether each company has been rated by the National Committee for Quality Assurance (NCQA).

You can also call insurance companies directly or work with an insurance agent. Agents do not charge you a fee — they are paid by the insurance company — but make sure any agent you work with is licensed in your state. Some agents specialize in Medicare and can explain the differences clearly. Others may push you toward plans that pay them higher commissions. If an agent pressures you or seems to be steering you away from the cheapest option without a clear reason, get a second opinion.

Write down the monthly premium, the deductible (if any), and what the plan covers for the services you use most. A plan that costs $20 less per month but has a higher deductible might cost you more overall if you see doctors frequently. Do the math for your own situation.

Special Rules for When You Turn 65 or Lose Other Coverage

If you are turning 65 and currently have health insurance through an employer or union, do not wait until you retire to think about Medicare. You need to enroll in Medicare Part A and Part B during your initial enrollment period, which starts three months before the month you turn 65 and ends three months after. If you miss this window, you may pay a permanent penalty on your Part B premium for every year you are on Medicare.

If you lose employer coverage before you turn 65 — because you retired early or lost your job — you have a special enrollment period to sign up for Medicare without penalty. This period lasts eight months from the date your coverage ends. During this time, you also have a may provide issue period to buy a supplement plan. Do not assume you can wait; the rules are strict, and penalties are permanent.

If you are currently on a Medicare Advantage plan and want to switch to Original Medicare plus a supplement, you can do so during the annual open enrollment period (October 15 through December 7 each year). When you switch to Original Medicare, you have a may provide issue period to buy a supplement plan, even if you missed your initial enrollment period years ago. This is one of the few second chances the system offers.

What Happens to Your Plan and Costs Each Year

Insurance companies raise supplement plan premiums every year, usually in January. The amount varies — sometimes a few dollars, sometimes $20 or more per month. At the same time, other companies may lower their prices or enter your market. A plan that was cheapest last year might not be this year.

Every fall, during open enrollment (October 15 through December 7), you can switch to a different supplement plan or a different insurance company. There is no penalty for switching, and you do not have to answer health questions if you are switching to a plan that covers the same or more benefits. This is the time to run the Medigap Plan Finder again, see what prices have changed, and decide whether staying put or switching saves you money.

Many people stay with the same plan for years without checking prices. Over time, this costs thousands of dollars more than shopping around. Set a reminder each October to spend 15 minutes comparing plans. If you find a cheaper option, call your current company and ask them to match it. If they will not, switch. Insurance companies count on people not bothering to look.

Questions to Ask Your Doctor or Insurance Agent

Before you choose a plan, think about the medical care you actually use. Do you take many medications? Do you see specialists? Do you go to the hospital or have outpatient surgery? Write down your typical year of medical visits and costs. Then ask an agent or your doctor's office which plan would cover those services with the lowest total cost to you.

Ask your insurance agent directly: "If I choose Plan G, what will I pay out of pocket for a doctor visit?" and "What will I pay for a hospital stay?" Get specific numbers, not general explanations. Ask whether the insurance company has a network — some supplement plans do not restrict which doctors you can see, but others do. Ask what happens if you travel out of state or go to an urgent care clinic.

If you are considering Plan N, ask about the copayments for services you use most. A $20 copayment per doctor visit adds up if you see a cardiologist, an endocrinologist, and your primary care doctor every three months. Do the math before you commit.

Frequently Asked Questions

Can I switch supplement plans if I change my mind after I buy one?

Yes, but the rules depend on timing. During your initial enrollment period (the first six months after you turn 65 and enroll in Part B), you can switch plans without health questions. After that period ends, you can still switch during the annual open enrollment period each fall, and you cannot be denied if you switch to a plan with equal or better coverage. If you want to switch to a plan with less coverage, the insurance company can ask health questions and deny you.

What if no insurance company will sell me a supplement plan because of my health?

This should not happen if you are within your may provide issue period. If an insurance company denies you during that window, contact your state insurance commissioner's office — they can force the company to sell you a plan. If you are outside your may provide issue period and multiple companies deny you, ask your state insurance commissioner about a high-risk pool or other options. Some states have programs for people who cannot obtain coverage.

Do I need to buy a supplement plan, or can I just use Original Medicare alone?

You can use Original Medicare without a supplement plan. You will pay copayments and coinsurance out of your pocket, and there is no annual out-of-pocket limit — theoretically, a serious illness could cost you tens of thousands of dollars. Many people choose this route if they are healthy and want to save on premiums. Just understand the financial risk you are taking.

If I am on Medicare Advantage, can I buy a supplement plan too?

No. Medicare does not allow you to have both a Medicare Advantage plan and a supplement plan at the same time. If you want a supplement, you must switch to Original Medicare first. You can do this during the annual open enrollment period, and when you do, you have a may provide issue period to buy a supplement plan.

What if I move to a different state after I buy a supplement plan?

Your supplement plan may not be sold in your new state, or the company may not operate there. Contact your insurance company as soon as you know you are moving. You will likely need to switch to a different plan or company. Because you are switching due to a move, you should have a may provide issue period in your new state, even if you are outside your initial enrollment period. Ask your insurance company about this before you move.