Medicare Supplement (Medigap)

What Medicare Supplement (Medigap) covers

Original Medicare covers most of your healthcare costs, but not all of them. You are responsible for a hospital deductible, 20% coinsurance for most doctor visits, and various copayments. A Medicare Supplement plan is private insurance that covers some or all of those remaining costs. Supplement plans are standardized by letter (Plan G, Plan N, etc.). The benefits are identical no matter which insurer you buy from, so price is the main differentiator.

• Part A hospital coinsurance: Hospital costs up to 365 days beyond Medicare's coverage.
• Part B coinsurance or copayment: The 20% of doctor and outpatient costs Medicare does not pay.
• Part A deductible: Covered in full by most plans.
• Skilled nursing coinsurance: Covered after day 20 of a qualifying stay.
• Foreign travel emergency: Covered at 80% on most plans, up to lifetime limits.

Who it is for

Supplement plans are a strong fit for people who want certainty about their out-of-pocket costs, use healthcare regularly, or travel within the U.S. and want to see any Medicare-accepting provider without network restrictions. Because Supplement plans do not include drug coverage, you will also need a separate Part D plan.

What Medicare Supplement Insurance is

Medicare Supplement Insurance, also called Medigap, is extra coverage sold by private insurance companies that helps pay the costs Original Medicare leaves to you. Original Medicare has two parts: Part A is hospital insurance, and Part B is medical insurance for doctor visits, outpatient care and equipment. Medicare pays its share of each covered bill first, and then your supplement policy pays its share. These plans are standardized by federal and state law, so a policy with the same letter offers the same basic benefits no matter who sells it. Price, service and how a company sets its rates are the real differences. You need both Part A and Part B to buy one, each policy covers one person so spouses need their own, and as long as you pay the premium the policy is guaranteed renewable even if your health changes.

How it works with the rest of Medicare

A supplement policy works only alongside Original Medicare, and that pairing is the point: you can see any doctor or hospital in the country that accepts Medicare, with no network and no referrals. It does not work with a Medicare Advantage plan, and an insurer cannot sell you a new policy while you are in one unless you are moving back to Original Medicare. Policies sold today also carry no drug coverage, so you add a stand-alone Medicare Part D prescription drug plan for that. For 2027, no Part D plan's deductible can exceed $700, and once your out-of-pocket drug spending reaches $2,400 you pay nothing for covered drugs for the rest of the year.

The lettered plans, A through N

In most states these plans come in ten standard letters: A, B, C, D, F, G, K, L, M and N. Plan A is the floor, covering the core benefits every plan must include, and every company that sells Medigap has to offer it. Each other letter adds more. Massachusetts, Minnesota and Wisconsin standardize their plans differently from the rest of the country.

• Plan G: Covers every gap Plan F does except the Part B deductible, including hospital and skilled nursing costs, excess charges and foreign travel emergencies. Often the first stop for people new to Medicare, because it leaves just one yearly charge to pay.
• Plan N: A lower premium than Plan G in many areas. In exchange you may pay up to $20 for some office visits and up to $50 for an emergency room visit that does not lead to admission, and it does not cover excess charges.
• High-deductible F and G: Lower premiums, but you pay the first $3,050 of covered costs yourself in 2027 before the coverage begins. CMS sets that amount each year.
• Plans C and F: Closed to anyone who became eligible for Medicare on or after January 1, 2020, because they pay the Part B deductible. If you were eligible before that date you may still be able to buy them.
• Plans K and L: Pay a percentage of many costs rather than the whole gap, so you share more of each bill, in return for a yearly cap on what you can pay. Plan K's cap is $8,000 for 2026; CMS has not published the 2027 figures.

What it covers, and what it does not

Depending on the letter, a policy can pay the Part A hospital deductible for each benefit period, extra hospital days after Medicare's run out, the Part B coinsurance that is usually 20% of the approved amount, excess charges when a doctor bills up to 15% above that amount, skilled nursing daily costs, hospice copayments, the first three pints of blood, and foreign travel emergencies up to the plan's limit. The Part B coinsurance is usually the biggest of those, because Original Medicare on its own has no yearly ceiling on what you can be charged. What it does not pay for is long-term or custodial care, routine dental, vision or hearing, private-duty nursing, or prescriptions. You also keep paying your Part B premium with any policy, and CMS has not announced the 2027 amount yet.

How premiums are set, and why two quotes differ

You pay the insurance company a monthly premium on top of what you pay Medicare, and companies are allowed to price the same lettered plan in three different ways. Community-rated means everyone pays the same regardless of age. Issue-age-rated is based on how old you were when you bought it, so it does not rise as you age. Attained-age-rated is based on your current age, so it does. All three can still rise with inflation. That is why comparing quotes only works letter against letter, and why asking how a company rates its premiums matters as much as the opening number.

The six-month window that decides whether you can buy

Here is the rule people miss most. Your Medigap Open Enrollment Period is a one-time, six-month window that starts the first month you are both 65 or older and enrolled in Part B. Inside it, a company must sell you any plan it offers in your state at the same price it charges a healthy applicant, with no medical underwriting and no refusal for a pre-existing condition. After it closes, insurers in most states can review your health history and may charge you more or decline you outright. Some states add protections such as a yearly switching window, so the rules where you live matter. There are also guaranteed issue rights that let you buy outside the window after certain events, such as losing employer coverage that paid after Medicare, or leaving an Advantage plan during a trial period. Buy outside those protections and a company may apply a waiting period before it covers a pre-existing condition.

If you are under 65

Medicare eligibility is not only about age. You can also qualify through a disability, end-stage renal disease or ALS. Federal law does not require insurers to sell a supplement policy to anyone under 65, though some states do require it, so this is another question that turns on where you live. If you are in that position now, you still get your own six-month window when you turn 65, and it works exactly as it does for everyone else.

Compared with Medicare Advantage

The honest version of Medigap vs. Medicare Advantage is that they are different trades rather than better and worse. With Original Medicare and a supplement you can use any provider in the country that accepts Medicare, you need no referrals, and your costs at the point of care are low or nothing, but you pay a supplement premium every month and buy drug coverage separately. With an Advantage plan the monthly premium is often far lower and the drug coverage and extras in one card, in exchange for a network, sometimes referrals, and copays until you reach the plan's yearly limit. Medigap tends to suit people who travel, see a lot of specialists, or simply want to know what a bad year costs. Putting Medicare together is a choice between this coverage and the alternatives, and the right one depends on your doctors, your prescriptions and your tolerance for surprise.

Common questions