Medicare Supplement Insurance Fills the Gaps That Original Medicare Leaves

Medicare Supplement insurance (also called Medigap) is a policy you buy from a private insurance company to pay for costs that Original Medicare does not cover. Original Medicare covers a large share of hospital and doctor bills, but it leaves you responsible for deductibles, copayments, and coinsurance. A Medigap policy picks up some or all of those out-of-pocket costs, depending on which plan you choose.

You do not need Medigap if you are in a Medicare Advantage plan instead of Original Medicare — Medicare Advantage plans include their own coverage for these costs. But if you use Original Medicare (Part A and Part B), Medigap is one way to reduce what you pay when you see a doctor or go to the hospital.

Key Takeaways

  • Medigap policies are sold by private insurance companies and cover deductibles, copayments, and coinsurance that Original Medicare does not pay.
  • There are ten standardized Medigap plans (A through N), and the benefits in each plan are the same no matter which company sells it — only the price differs.
  • You can buy Medigap only if you have Original Medicare Part A and Part B; you cannot use it with Medicare Advantage.
  • The best time to buy Medigap is during your six-month open enrollment period starting the month you turn 65 and enroll in Part B, because insurers cannot deny you or charge more based on health conditions during this window.
  • Medigap premiums vary by age, location, and the insurance company, and they increase as you get older.

The Ten Medigap Plans and What Each One Covers

Insurance companies can only sell ten standardized Medigap plans, labeled A through N. The federal government sets what each plan must cover, so a Plan G from one company covers exactly the same things as a Plan G from another company. The only difference is the monthly premium you pay.

Plan A is the most basic and least expensive. It covers the Part A deductible, Part B coinsurance, and some hospital costs. Plan G covers almost everything except the Part B deductible (which is $240 in 2024, though this amount changes yearly). Plan N is less expensive than Plan G but requires you to pay small copayments at doctor visits and the emergency room.

Plans B, C, D, F, K, L, and M fill in different combinations of gaps. Plan F was once the most popular because it covered everything, but it is no longer sold to people newly turning 65 — only to those who were already on Medicare before 2020. If you are newly may be able to access for Medicare, your main choices are Plans A, G, and N, though all ten remain available to existing Medicare beneficiaries.

You can compare what each plan covers using the official Medicare Plan Finder tool on Medicare.gov, which shows you the exact benefits and costs for plans available in your zip code.

How Medigap Premiums Work and What Affects Your Cost

Medigap premiums are what you pay monthly to the insurance company. Three things determine your premium: the plan you choose (Plan G costs more than Plan A), your age, and your location. Some companies also factor in your health history, but only if you buy outside the open enrollment period.

Insurance companies use one of three rating methods. Community rating means everyone in your area pays the same premium regardless of age. Issue-age rating bases your premium on your age when you buy the policy — younger buyers pay less and their premium stays lower as they age. Attained-age rating increases your premium every year as you get older, so your cost rises over time even if you stay with the same company.

Premiums also vary significantly by state and by company. The same Plan G might cost $120 a month in one state and $200 in another, or $150 with one insurer and $180 with another in the same area. Shopping around and comparing quotes from multiple companies can save you hundreds of dollars a year.

When You Can Buy Medigap and Avoid Higher Costs

The best time to buy Medigap is during your open enrollment period, which lasts six months starting the month you turn 65 and enroll in Medicare Part B. During this window, insurance companies must sell you any Medigap plan and cannot charge you more or deny you coverage based on pre-existing health conditions.

If you miss this window, you can still buy Medigap later, but insurers may deny you, charge you a higher premium, or exclude coverage for conditions you already have. Some states have additional protections that allow you to buy Medigap later without penalty, but these vary. The safest approach is to enroll during your open enrollment period.

You also have a may provide issue period if you drop a Medicare Advantage plan and want to switch to Original Medicare with Medigap. This period is usually 63 days from the date your Medicare Advantage coverage ends. During this time, Medigap insurers must sell you a policy without medical underwriting or waiting periods.

How Medigap Works Alongside Original Medicare

When you see a doctor or go to the hospital, Original Medicare pays its share first, then your Medigap policy pays its share. You send the bill to Medicare, Medicare processes it and pays what it covers, then the claim goes to your Medigap insurer, which pays what the Medigap plan covers. In most cases, you do not pay anything out of pocket.

Your Medigap policy works with Medicare Part A (hospital insurance) and Part B (medical insurance). It does not cover prescription drugs — you need a separate Part D plan for that. It also does not cover dental, vision, hearing aids, or long-term care, even though some Medigap plans offer limited dental or vision discounts through partner networks.

You keep your Medigap policy as long as you pay the premium and remain enrolled in Medicare Part A and Part B. If you switch to Medicare Advantage, your Medigap policy ends, though you can switch back to Original Medicare and Medigap later during the annual open enrollment period (October 15 to December 7).

Medigap Versus Medicare Advantage: Which Path Costs Less

The choice between Medigap and Medicare Advantage depends on your health, your doctors, and your budget. With Original Medicare and Medigap, you can see any doctor or hospital that accepts Medicare, and your out-of-pocket costs are predictable. With Medicare Advantage, you usually pay a lower or zero monthly premium, but you have a network of doctors and hospitals, and your total costs depend on how much care you use.

If you are healthy and rarely see a doctor, Medicare Advantage may cost less. If you have multiple chronic conditions and see specialists regularly, Medigap may cost less because you have no network restrictions and your copayments are capped. Run the numbers for your situation using the Medicare Plan Finder, which shows estimated costs for both paths based on your zip code and the plans available to you.

You cannot have both Medigap and Medicare Advantage at the same time. You must choose one path when you enroll in Medicare, though you can switch between them during the annual open enrollment period.

How to Shop for and Enroll in a Medigap Plan

Start by visiting Medicare.gov and using the Plan Finder tool. Enter your zip code and the plans you want to compare. The tool shows you which plans are sold in your area, what each one covers, and the monthly premium from each company.

Call or visit the websites of the insurance companies that offer the plans you are interested in. Ask for a quote and ask whether they use community rating, issue-age rating, or attained-age rating. Ask whether they have any discounts (some offer discounts for paying by automatic bank withdrawal or for being a member of certain organizations).

Once you choose a plan and company, you can enroll online, by phone, or by mail. The insurance company will send you a policy document that explains your coverage, your premium, and how to file claims. Your coverage usually starts on the first day of the month after the company receives your enrollment form.

Frequently Asked Questions

Can I switch Medigap plans if I change my mind?

Yes, you can switch to a different Medigap plan or company at any time, though the new company may underwrite your health if you are outside your open enrollment period. The easiest time to switch is during your open enrollment period or during the annual Medicare open enrollment period (October 15 to December 7), when you can change plans without medical review.

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

Your Medigap policy may not be valid in your new state because insurance is regulated by state. Contact your current Medigap insurer to ask whether they operate in your new state. If not, you will need to buy a new policy from a company that does business there. During your move, you may have a may provide issue period to buy Medigap without medical underwriting.

Does Medigap cover prescription drugs?

No. Medigap covers only the gaps in Original Medicare Parts A and B. You need a separate Medicare Part D prescription drug plan to cover medications. You can enroll in Part D at the same time you enroll in Medicare, or during the annual open enrollment period.

What if I cannot afford a Medigap premium?

Some states offer programs that help low-income seniors pay Medigap premiums, though these vary by state. Contact your State Health Insurance information Program (SHIP) to learn what programs exist in your area. You can also ask your Medigap insurer whether they offer discounts or payment plans.

Can I buy Medigap if I have a pre-existing condition?

During your open enrollment period, yes — insurers cannot deny you or charge more based on health conditions. Outside this window, insurers can underwrite your health and may deny you, charge more, or exclude coverage for certain conditions. This is why enrolling during your open enrollment period is so important.