Start by understanding what you actually need to cover

A Medicare supplement plan (also called Medigap) fills the gaps that Original Medicare leaves behind — copayments, coinsurance, and deductibles. Before you compare plans, figure out what gaps matter most to you. If you see a lot of doctors or specialists, you'll pay more in copayments. If you travel or live part of the year in another state, you need to know which plans work outside your home area. If you take expensive medications, Medicare Part D (prescription drug coverage) is separate from Medigap and needs its own decision.

The first step is honest: how much medical care do you actually use? Look back at last year. How many doctor visits, hospital stays, or specialist appointments did you have? What did you pay out of pocket? That number tells you whether you need a plan that covers a lot of small costs or one that mainly protects you from catastrophic bills.

Key Takeaways

  • Medicare supplement plans are standardized by the federal government, so Plan G from one insurer covers exactly the same things as Plan G from another — only the price differs.
  • Plan G and Plan N are the most common choices for new enrollees, with Plan G covering more but costing more per month.
  • Your best enrollment window is within 63 days of turning 65 or first enrolling in Medicare Part B, when insurers cannot deny you or charge more based on health history.
  • Once you miss that window, insurers can reject you or charge higher premiums, so timing your enrollment matters more than picking the perfect plan.
  • Prices vary by insurer and location, so getting quotes from at least three companies in your area is the only way to find the lowest cost for the plan you want.

Know the ten standardized plans and which ones most people choose

The federal government sets what each Medicare supplement plan must cover. There are ten plans, labeled A through N (skipping E, H, I, and J). Plan A is the most basic. Plan G covers almost everything except the Part B deductible. Plan N is in the middle — it covers most things but leaves you paying some copayments at the doctor's office and emergency room.

Most people choose between Plan G and Plan N. Plan G costs more per month but saves you money if you go to the doctor frequently, because it covers the Part B deductible (the amount you pay before Medicare starts sharing costs). Plan N costs less per month but you pay a copayment each time you see a doctor — usually $20 per visit. If you rarely see doctors, Plan N might cost less overall. If you see doctors monthly or more, Plan G usually wins.

Plan F used to be the most popular, but it is no longer sold to people new to Medicare (only to those who had it before 2020). If you are new to Medicare, you cannot buy Plan F, so do not spend time comparing it.

Understand the enrollment window and why it matters

You have a 63-day window to buy a Medicare supplement plan without the insurance company asking about your health or charging you extra. This window starts when you turn 65 and enroll in Medicare Part B, or when you first become may be able to access for Medicare if you are already 65. If you enroll in that window, the insurer must sell you any plan you want at the standard price for your age and location.

If you miss that window, everything changes. After 63 days, insurers can ask detailed health questions, deny you coverage, or charge you a higher premium because of pre-existing conditions. Some insurers will not sell to you at all. You can still buy a plan, but you lose the protection that makes the first 63 days so valuable. Many people who wait end up paying hundreds of dollars more per year, or they find that the plan they want is not available to them.

Mark your calendar. If you turn 65 on March 15, your window closes on May 17. If you are already 65 and just now enrolling in Medicare, your window closes 63 days after you enroll in Part B. Do not assume you can shop around for months — you cannot, not without risk.

Get quotes from at least three insurers in your area

The same plan costs different amounts depending on which insurance company sells it and where you live. Plan G from Aetna might cost $140 a month in one county and $165 in the next county over. Plan G from United Healthcare in that same county might cost $155. The difference adds up: over five years, picking the cheapest Plan G instead of the most expensive one can save you $3,000 or more.

You need quotes from at least three insurers. Call them directly or visit their websites. Have your Medicare card handy — they will ask for your Medicare number. Tell them your birth date, the state you live in, and which plan you are interested in. Ask for the monthly premium and whether there are any discounts (some insurers offer discounts if you pay by automatic bank transfer, or if you are a member of AARP). Write down the numbers so you can compare.

Do not rely on online comparison tools alone. Some tools do not include all insurers in your area, and some show outdated prices. Getting quotes directly from insurers takes 15 minutes per company and gives you current, accurate information.

Consider whether you move seasonally or travel often

Most Medicare supplement plans work anywhere in the United States, but a few do not. If you spend winters in Florida and summers in Maine, or if you travel frequently, you need a plan that covers you in all 50 states. Plans A, B, C, D, G, M, and N all work nationwide. Plans K and L have limits outside your home state. Plans F and J (which you cannot buy anyway if you are new to Medicare) also have limits.

If you stay in one state year-round, this does not matter. If you move or travel, ask the insurer directly: "Does this plan cover me in all 50 states, or only in my home state?" Write down the answer. A plan that does not cover you when you are away from home is not a plan — it is a liability.

Decide on prescription drug coverage separately

Medicare supplement plans do not cover prescription drugs. You need to choose a Part D plan (prescription drug coverage) separately, even if you do not take medications now. If you do not enroll in Part D when you first become may be able to access for Medicare, you may pay a penalty for every month you go without it, even if you enroll later.

Part D plans change every year — the drugs they cover, the copayments, and the premiums. You can switch Part D plans once a year during the annual enrollment period (October 15 to December 7). Your Medicare supplement plan does not change, so you can keep the same Medigap plan while switching Part D plans as your medications or costs change.

Enroll during your 63-day window

Once you have decided on a plan and a company, contact the insurer directly to enroll. You can call, go online, or visit an agent in person. Have your Medicare card and Social Security number ready. The insurer will ask you to confirm your health history — answer honestly. During your 63-day window, your answers do not affect whether you are accepted or what you pay, but lying on the process can cause problems later if you file a claim.

Ask when your coverage starts. Most plans start on the first of the month following your enrollment, but some start sooner. Ask whether there is a waiting period for any services (some plans have short waiting periods for certain conditions). Get a confirmation number and a copy of your policy documents. Keep these documents — you will need them when you use your coverage.

Review your choice each year, but do not switch plans lightly

Once a year, during the annual enrollment period (October 15 to December 7), you can switch to a different Medicare supplement plan or a different insurer. Many people do not realize they can switch, so they stay with a plan that has gotten expensive. If you have been with the same insurer for years and your premium has climbed, get quotes from other companies. You might find the same plan for $30 or $40 less per month elsewhere.

However, switching plans has a cost: if you have health problems that developed after your original 63-day window, a new insurer can deny you or charge you more. If you are healthy and your current plan is expensive, switching makes sense. If you have ongoing health issues, staying put may be safer, even if the premium is higher. Think through the trade-off before you switch.

Frequently Asked Questions

Can I buy a Medicare supplement plan if I am already on Medicare?

Yes, but the rules depend on when you enrolled in Medicare Part B. If you enrolled in Part B fewer than 63 days ago, you are still in your open enrollment window and can buy any plan at standard rates. If it has been longer than 63 days, insurers can ask health questions and charge you more or deny you coverage. Contact insurers in your area to find out what they will offer you.

What is the difference between a Medicare supplement and a Medicare Advantage plan?

A Medicare supplement (Medigap) works with Original Medicare — you keep your Medicare card and see any doctor who accepts Medicare. A Medicare Advantage plan replaces Original Medicare and usually has a network of doctors you must use. Supplement plans have higher monthly premiums but lower copayments. Advantage plans have lower premiums but higher copayments and network restrictions. They are different products for different needs.

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

You can use Original Medicare alone, but you will pay copayments and coinsurance for every service. A supplement plan costs money each month but reduces what you pay when you use care. Whether it makes sense depends on how much medical care you use. If you rarely see doctors, Original Medicare alone might cost less. If you see doctors regularly, a supplement plan usually saves money overall.

Will my Medicare supplement premium go up every year?

Yes. Premiums increase most years, though the amount varies by insurer and plan. Some increases are small (2 to 3 percent), and some are larger (5 to 10 percent or more). You cannot control the increases, but you can shop around each year during the annual enrollment period to see whether a different insurer offers the same plan for less money.

What happens if I move to a different state?

Your Medicare supplement plan continues to work in your new state — the coverage does not change. However, the premium might change because rates vary by location. Contact your insurer to update your address and ask whether your premium will change. You can also shop around during the annual enrollment period to see whether other insurers in your new state offer better prices.