How Medicare Works with Supplemental Insurance

Rules differ for disability and end-stage renal disease; confirm with your plans.

Medigap policies are standardized by plan letter and pay after Original Medicare. With Plan G, after the Part B deductible, Medicare-approved care is generally covered in full.

Medigap benefits are standardized by plan letter. Prices vary by insurer, age, ZIP code and tobacco use.

If you have coverage from a current employer, you may not need Medigap yet, and delaying Part B can preserve your Medigap Open Enrollment Period for later. Retiree coverage is different: it may work like a supplement, so compare it with Medigap before dropping it, because you may not be able to get retiree coverage back.

When employer or union coverage that pays after Medicare ends, you generally have a guaranteed issue right to buy certain Medigap plans.

TRICARE For Life is Medicare-wraparound coverage for military retirees with Part A and Part B. It pays after Medicare for services both cover, and its pharmacy coverage is creditable, so most TFL beneficiaries do not need Medigap or Part D.

If your income and savings are limited, two programs can cut your Medicare costs sharply:

If you qualify for both Medicare and full Medicaid, you may also be able to join a Dual Special Needs Plan. See help for low-income Part D beneficiaries.

Medicare Advantage replaces Original Medicare rather than supplementing it. Medigap cannot pay Medicare Advantage costs, so people choose one path or the other.

A Medicare Supplement plan is built to cover the gaps in Original Medicare. These are the costs it can pick up:

The method depends on the insurer and the state. Ask how a policy is priced before you buy, not just what it costs today.

Federal law also gives you guaranteed issue rights in certain situations, generally within 63 days after other coverage ends:

For 2027, a standalone Part D plan has a maximum deductible of $700 and an out-of-pocket cap of $2,400. Buy one when you buy Medigap to avoid a lifelong late enrollment penalty.

Doctors who “accept assignment” agree to take Medicare’s approved amount as full payment. Doctors who do not accept assignment can charge up to 15% more, called a Part B excess charge. Plans F and G cover excess charges; Plan N and most other plans do not.

Most doctors accept assignment, and some states limit or prohibit excess charges, so for many people the risk is small. Ask your doctors whether they accept assignment before deciding whether excess charge coverage is worth paying for.

Your six-month Medigap Open Enrollment Period starts the first month you are both 65 or older and enrolled in Part B. It happens only once and cannot be restarted. During it, insurers must sell you any Medigap plan they offer in your state, at the same price as people in good health.

If you keep working past 65 with employer coverage and delay Part B, your Medigap Open Enrollment Period waits until you enroll in Part B. Enrolling in Part B early, when you do not need it, starts the clock and can waste this protection.

Some insurers sell Medicare SELECT policies, a type of Medigap that requires you to use specific hospitals, and sometimes doctors, for non-emergency care in exchange for a lower premium. Benefits match the standard plan letter, but the network rule makes them work more like a managed plan. If you want any-doctor freedom, choose a standard Medigap policy instead.

Consider a hospital stay. Without a supplement, you pay the Part A deductible for each benefit period, $1,736 in 2026, plus 20% of the doctors’ Part B bills while you are in the hospital, with no cap. With Plan G, the Part A deductible and your Part B coinsurance are covered; after the yearly Part B deductible, you generally pay nothing for Medicare-approved care.

If you buy Medigap during your open enrollment period or with a guaranteed issue right, you generally cannot be denied or charged more for health conditions. However, if you did not have creditable coverage before, an insurer may impose a waiting period of up to six months before covering costs for a pre-existing condition. Prior creditable coverage reduces or removes that waiting period.

If you replace one Medigap policy with another, you generally get 30 days to decide whether to keep the new policy. Pay the premiums for both during that time, and do not cancel your old policy until you are sure about the new one.

If a quote includes an introductory discount, ask what the premium becomes after it ends.

If you have full Medicaid, you generally do not need Medigap, and insurers generally cannot sell you a policy that duplicates Medicaid benefits. If you qualify for a Medicare Savings Program, it may pay your Part B premium and, in some cases, deductibles and coinsurance; check whether a Medigap policy still adds value for you.

Federal law sets exactly what each plan letter covers, so the same letter has the same benefits from every insurer in your state.

*Plans C and F can only be bought by people who were eligible for Medicare before January 1, 2020. **Plans K and L have a yearly out-of-pocket limit that Medicare sets each year; after you reach it, the plan pays 100% of covered services for the rest of the year. ***Plan N pays all Part B coinsurance except copays of up to $20 for some office visits and up to $50 for emergency room visits that do not lead to an inpatient admission. Massachusetts, Minnesota and Wisconsin standardize their plans differently.

Most people new to Medicare choose one of these three. Plan G covers every gap except the Part B deductible. Plan N trades a lower premium for copays of up to $20 for some office visits and up to $50 for ER visits that do not lead to admission, and it does not cover Part B excess charges. High-Deductible Plan G has a $3,050 deductible for 2027, up from $2,950, then covers like Plan G. See Plan G vs Plan N.

Plans K and L pay a share of most costs instead of all of them: Plan K pays 50% and Plan L pays 75% of most cost sharing, after which you pay the rest. In exchange for lower premiums, both have a yearly out-of-pocket limit that Medicare sets each year. Once you reach it, the plan pays 100% of covered services for the rest of the year.

These plans can suit people who want catastrophic protection at a lower premium and can handle some costs along the way. Ask whether your insurer offers Plan K or L in your state.

Plans C and F are the only plans that cover the Part B deductible. Since January 1, 2020, they cannot be sold to people newly eligible for Medicare. If you were eligible for Medicare before that date, even if you did not enroll, you may still be able to buy Plan C or F, including a High-Deductible Plan F with the same $3,050 deductible for 2027.

For most people who can buy either, compare the yearly premium difference between Plan F and Plan G with the Part B deductible. If Plan F costs more than the deductible saves you, Plan G is the better value.

If you have Medicare before 65 because of a disability or end-stage renal disease, federal law does not require insurers to sell you a Medigap policy, but many states do. Prices for people under 65 can be much higher, and plan choices may be limited. When you turn 65, you get a new six-month Medigap Open Enrollment Period, when you can buy any plan sold in your state at the same prices as everyone else your age.

Inside the U.S., a Medigap plan follows you everywhere, because it works with any provider that accepts Medicare. Outside the U.S., Original Medicare generally pays nothing, but Plans C, D, F, G, M and N cover 80% of emergency care abroad after a $250 yearly deductible, up to a $50,000 lifetime limit.

Medigap benefits never change once you buy, but premiums can. Insurers file rate increases with state regulators, often once a year. Because the same plan letter covers the same benefits everywhere, switching to a lower-priced insurer can save money without changing your coverage.

The catch is underwriting. Outside your Medigap Open Enrollment Period or a guaranteed issue situation, most states let the new insurer ask health questions and decline you. Never cancel your current policy until the new one is approved and in force.

In most cases you never file a Medigap claim. Your doctor bills Medicare, Medicare pays its share, and the claim crosses over to your Medigap insurer automatically, which pays its share. You get a Medicare Summary Notice and an explanation of benefits showing what each paid.

Because Medigap plans sold today do not cover prescriptions, you should also have a Part D plan. It does not have to come from your Medigap company. Choose it by your drugs and pharmacy in Medicare Plan Finder, and review it every fall. If you delay drug coverage without other creditable coverage, the late penalty adds 1% of the national base beneficiary premium, $41.33 for 2027, for every month you went without.

If you turn 65 in 2027, your Initial Enrollment Period lasts seven months: the three months before your birthday month, your birthday month and the three months after. Signing up during the first three months means your coverage starts on the first day of your birthday month.

You do not have to compare plans alone, and you should not have to pay for help. These are the free options:

Before any call, have your Medicare card, your list of drugs and doses, your doctors and your preferred pharmacies ready. It turns a long conversation into a short one.