Fifty-nine terms. House rule: no definition here uses a word that itself needs this glossary. Each one also says why it matters to you, not just what it means.
A form a doctor or supplier asks you to sign when they think Medicare will not pay for something they are about to do.
Why it matters. Signing it means you agree to pay if Medicare says no. You are allowed to ask what it will cost before you sign, and you are allowed to say no.
See also: Coinsurance, Medically necessary
October 15 to December 7 every year. The stretch when anyone on Medicare can change their Medicare Advantage plan or their drug plan.
Why it matters. Whatever you choose starts on January 1. This is the one window most people actually need to remember.
See also: Medicare Advantage Open Enrollment, Initial Enrollment Period, General Enrollment Period, Special Enrollment Period
Asking Medicare or your plan to look again at a decision to not pay for something.
Why it matters. A surprising number of first decisions get reversed. There are five levels, and the first one is a form. Do not treat a denial as the end.
See also: Denial, Explanation of Benefits
A doctor who “accepts assignment” has agreed to take the Medicare-approved amount as full payment.
Why it matters. If they do not accept assignment, they can charge you up to 15% more, which is called an excess charge. Most doctors do accept it, but it is worth asking.
See also: Excess charges, Medicare-approved amount
The clock Part A uses. It starts the day you go into a hospital and ends when you have been out for 60 days in a row.
Why it matters. If you go back in after 60 days out, a brand new deductible applies. Two hospital stays in one calendar year can mean paying the hospital deductible twice.
See also: Deductible, Part A
The point in the year when you have spent enough of your own money on covered prescriptions that your drug plan pays the rest.
Why it matters. Since 2025 this is a hard ceiling. In 2026 it is $2,100. Once you reach it, covered drugs cost you nothing for the rest of the calendar year.
See also: Part D, Out-of-pocket maximum, Medicare Prescription Payment Plan
A share of the bill written as a percentage. Under Part B it is usually 20% of the Medicare-approved amount.
Why it matters. A percentage of an unknown number is an unknown number. Original Medicare puts no ceiling on your 20%, which is the whole reason supplements and Advantage plans exist.
See also: Copayment, Deductible, Medicare-approved amount
A flat dollar amount you pay for a visit or a prescription. Twenty dollars to see the doctor, for example.
Why it matters. Copays are easier to plan around than coinsurance, because you know the number in advance. Medicare Advantage plans lean on copays; Original Medicare leans on coinsurance.
See also: Coinsurance
Drug coverage from somewhere else, usually an employer or a union, that is at least as good as a Medicare drug plan.
Why it matters. If your coverage is creditable, you can delay Part D with no penalty. Your employer must send you a letter each fall saying whether it is. Keep that letter.
See also: Late enrollment penalty, Part D, Special Enrollment Period
The amount you pay yourself before the coverage starts paying.
Why it matters. In 2026 the Part B deductible is $283 for the year. The Part A hospital deductible is about $1,736 and it applies per benefit period, not per year.
See also: Benefit period, Coinsurance
A decision by Medicare or your plan not to pay for something.
Why it matters. A denial letter must tell you why and how to appeal. If it does not, that itself is worth a phone call.
See also: Appeal, Prior authorization
Equipment you use at home for a medical reason: a walker, a wheelchair, a hospital bed, an oxygen concentrator, a blood-sugar monitor.
Why it matters. Part B covers it at 80% after the deductible, but only from a supplier that takes Medicare. Buying it yourself at a pharmacy usually means paying for all of it.
See also: Part B, Assignment
The extra amount, up to 15%, that a doctor who does not accept assignment can add to a Part B bill.
Why it matters. Medigap Plan G covers these. Plan N does not. In a handful of states excess charges are banned outright.
See also: Assignment, Plan G, Plan N
The statement your plan sends after a claim. It is not a bill.
Why it matters. It shows what was charged, what the plan paid and what you may owe. Compare it against the bill you get from the doctor; they should agree.
See also: Medicare Summary Notice, Appeal
A federal program that pays most of the cost of a Part D drug plan for people with limited income and savings.
Why it matters. It is worth thousands a year and many people who qualify never apply. You apply through Social Security, and applying is free.
See also: Part D, Medicare Savings Program
The list of prescription drugs a particular drug plan agrees to cover, and what tier each one sits in.
Why it matters. Two plans with the same monthly price can differ by thousands of dollars a year for the same prescriptions. The formulary is the whole ballgame. Check yours every fall, because it changes.
See also: Tier, Part D, Prior authorization
January 1 to March 31, for people who missed their first chance to sign up for Part A or Part B and have no other reason to delay.
Why it matters. Since 2023 your coverage starts the first day of the month after you sign up, instead of waiting until July. A late-enrollment penalty may still apply.
See also: Initial Enrollment Period, Late enrollment penalty, Special Enrollment Period
A situation where a Medigap company must sell you a policy and cannot charge you more or refuse you because of your health.
Why it matters. You get one automatically during your six-month Medigap open enrollment. After that, guaranteed issue only appears in specific circumstances, such as an employer plan ending or a plan leaving your area.
See also: Medigap open enrollment, Medical underwriting, Medigap
The same coverage as Plan G, but you pay a few thousand dollars of Medicare-covered costs yourself each year before it starts.
Why it matters. The monthly premium is far lower. It suits people who are healthy, have savings, and want protection against a catastrophe rather than help with routine bills.
A type of Medicare Advantage plan that only pays for care from doctors and hospitals inside its own network, except in an emergency.
Why it matters. HMOs usually cost less each month and usually require a referral to see a specialist. If your doctors are all in the network, that trade can be worth it.
Comfort care for someone expected to live six months or less, at home or in a facility, covered by Part A.
Why it matters. Part A covers hospice even if you are in a Medicare Advantage plan. It includes support for the family, not only the patient.
See also: Part A
Your first chance to sign up: a seven-month stretch made of the three months before the month you turn 65, that month, and the three months after.
Why it matters. Sign up before your birthday month and coverage starts on the first of your birthday month. Sign up during or after it and coverage starts the first of the month after you sign up. Earlier is simply better.
See also: General Enrollment Period, Special Enrollment Period, Annual Enrollment Period, Late enrollment penalty
Formally admitted to the hospital by a doctor. Part A pays for inpatient stays.
Why it matters. You can spend two nights in a hospital bed and still be an outpatient on observation, which Part B pays for instead, at 20% with no cap. Ask, out loud, “am I admitted as an inpatient?”
See also: Observation status, Part A, Part B
An extra amount added to your Part B and Part D premiums if your income was above a threshold two years ago.
Why it matters. In 2026 it starts above roughly $109,000 for one person or $218,000 for a couple filing jointly, based on your 2024 tax return. If your income has since dropped because you retired, you can ask Social Security to reconsider using form SSA-44.
A permanent increase to your monthly premium for signing up late without a good reason.
Why it matters. Part B adds 10% for every full year you could have had it and did not, for as long as you have Part B. Part D adds 1% of the national base premium for every month you went without creditable drug coverage, also for as long as you have Part D.
See also: Creditable coverage, General Enrollment Period, Initial Enrollment Period
When an insurance company asks about your health before deciding whether to sell you a policy, and at what price.
Why it matters. Medigap companies may do this outside your protected windows. It is why the six months after your Part B starts matter so much.
See also: Guaranteed issue right, Medigap open enrollment
Needed to diagnose or treat a condition, and meeting accepted standards of medicine.
Why it matters. It is the test Medicare applies to almost everything. Comfort, convenience and cosmetic reasons do not pass it.
See also: Advance Beneficiary Notice
The federal health insurance program for people 65 and over, and for some younger people with disabilities or end-stage kidney disease.
Why it matters. It is not one thing. It is four parts you assemble, which is exactly why it feels complicated.
A plan from a private company that replaces Original Medicare. It must cover everything Parts A and B cover, and usually adds drug coverage.
Why it matters. It often costs less each month and includes extras like dental. In exchange you use a network, you may need referrals and prior approvals, and you cannot easily go back to a Medigap policy later.
See also: Part C, HMO, PPO, Network, Prior authorization, Star Ratings
January 1 to March 31. If you are already in a Medicare Advantage plan on January 1, you get one change.
Why it matters. You can switch to a different Advantage plan, or drop back to Original Medicare and pick up a drug plan. It does nothing for you if you are on Original Medicare, and it does not guarantee you a Medigap policy.
See also: Annual Enrollment Period, Part C, Guaranteed issue right
An option to spread what you owe for prescriptions across monthly bills instead of paying it all at the pharmacy counter.
Why it matters. It does not lower your total cost. It stops a $900 January from happening. You have to ask your drug plan to turn it on.
See also: Part D, Catastrophic coverage
State programs that pay your Part B premium, and sometimes your deductibles and coinsurance, if your income and savings are below a limit.
Why it matters. Qualifying for one also enrolls you automatically in Extra Help for your drugs. The limits are higher than most people expect.
See also: Extra Help, Premium
A quarterly statement of everything billed to Original Medicare in your name. It is not a bill.
Why it matters. Read it. It is how most people spot a charge for a service they never received.
See also: Explanation of Benefits
The price Medicare has decided a service is worth. Your 20% is 20% of this number, not of whatever the office bills.
Why it matters. It is why a $900 bill can turn into a $52 payment. The approved amount is almost always lower than the sticker price.
See also: Coinsurance, Assignment
A private policy that sits behind Original Medicare and pays the deductibles and coinsurance Medicare leaves you.
Why it matters. Plans are standardized by letter, so Plan G from one company covers exactly what Plan G covers from another. Only the price and the service differ.
See also: Plan G, Plan N, Plan K and Plan L, Plan F, Medigap open enrollment
A one-time six-month window that starts the month you are both 65 and enrolled in Part B.
Why it matters. During it, any company must sell you any Medigap plan they offer at their best rate, whatever your health. This window does not come back, and missing it is the single most expensive mistake people make.
See also: Guaranteed issue right, Medical underwriting, Medigap
The doctors, hospitals and pharmacies a plan has a contract with.
Why it matters. Networks change every January. A plan that was perfect last year can drop your specialist this year, and the letter telling you so will not lead with that fact.
See also: HMO, PPO, Medicare Advantage
Being kept in a hospital for monitoring without being formally admitted. You are an outpatient, even in a hospital bed.
Why it matters. Part B pays instead of Part A, so you owe 20% with no ceiling. It can also disqualify you from Medicare-covered skilled nursing care afterwards, which needs a three-day inpatient stay.
See also: Inpatient, Skilled nursing facility care, Part B
Part A and Part B together, run by the federal government. Any doctor in the country who takes Medicare will see you.
Why it matters. No network, no referrals, no prior approvals. In exchange there is no cap on your 20%, so most people add either a Medigap policy or choose Medicare Advantage instead.
See also: Part A, Part B, Medigap, Medicare Advantage
The most you can be made to pay in a year before the plan covers everything else.
Why it matters. Medicare Advantage plans must have one for medical care. Original Medicare has none at all. Part D has one for drugs: $2,100 in 2026.
See also: Catastrophic coverage, Medicare Advantage, Coinsurance
The hospital half. Inpatient stays, skilled nursing care after a hospital stay, hospice and some home health care.
Why it matters. Most people pay nothing each month for Part A, because ten years of payroll taxes already paid for it. You still owe the hospital deductible each benefit period.
See also: Part B, Benefit period, Skilled nursing facility care, Inpatient
The doctor half. Office visits, tests, scans, outpatient surgery, equipment and preventive care.
Why it matters. The standard premium in 2026 is $202.90 a month, usually taken straight out of your Social Security payment. After a $283 yearly deductible you pay 20% of everything, with no ceiling.
See also: Part A, Premium, IRMAA, Durable medical equipment, Coinsurance
The formal name for Medicare Advantage: a private plan that delivers your Part A and Part B benefits in one package.
Why it matters. You still pay your Part B premium when you are on Part C. The plan itself may cost nothing extra on top, which is where the “$0 plan” language comes from.
See also: Medicare Advantage, Star Ratings
Prescription drug coverage, sold by private companies and approved by Medicare.
Why it matters. You need it, or other coverage at least as good, from the moment you are eligible, or a penalty follows you for life. It is also the plan most worth re-checking every fall.
See also: Formulary, Tier, Creditable coverage, Late enrollment penalty, Catastrophic coverage
The Medigap plan that used to cover everything, including the Part B deductible.
Why it matters. It is closed to anyone who became eligible for Medicare on or after January 1, 2020. If you already have it you may keep it, though the pool of people in it is aging and prices tend to climb.
The Medigap plan most people buy now. It covers everything Plan F covered except the Part B deductible.
Why it matters. You pay $283 in 2026 and then essentially nothing else for Medicare-approved care. It also covers excess charges, which Plan N does not.
See also: Plan N, Plan F, Excess charges, High-deductible Plan G
Medigap plans that pay a share of your costs rather than all of them: Plan K pays 50%, Plan L pays 75%.
Why it matters. Both have a yearly out-of-pocket limit, after which they pay everything. Lower premiums, more exposure in a bad year. The limits change annually.
See also: Medigap, Plan G, Out-of-pocket maximum
A Medigap plan with a lower premium than Plan G. You pay the Part B deductible, up to $20 for most office visits, and up to $50 for an emergency room visit that does not lead to admission.
Why it matters. It suits people who see the doctor a few times a year. It does not cover excess charges, so it matters more if your doctors do not accept assignment.
See also: Plan G, Excess charges, Medigap
A type of Medicare Advantage plan that will pay for care outside its network, but at a higher share of the cost to you.
Why it matters. More freedom than an HMO, usually a higher premium, and usually no referral needed. Check what “out of network” actually costs before you rely on it.
See also: HMO, Medicare Advantage, Network
The amount you pay every month to keep coverage, whether or not you use it.
Why it matters. Part B in 2026 is $202.90 for most people. Part A is usually $0. A Medigap or Advantage plan adds its own premium on top of Part B.
See also: IRMAA, Part B, Deductible
Screenings, shots and check-ups Medicare covers to catch problems early.
Why it matters. Most cost you nothing at all: no deductible, no 20%. That includes an annual wellness visit, flu and shingles vaccines, and several cancer screenings.
See also: Part B, Welcome to Medicare visit
Approval a plan requires before it will pay for a service or a drug.
Why it matters. Original Medicare rarely asks for it. Medicare Advantage plans often do, and it is the most common source of frustration people bring us. Ask which services need it before you enroll.
See also: Medicare Advantage, Denial, Appeal
A change in your circumstances that opens a special window to enroll or switch outside the usual dates.
Why it matters. Moving, losing employer coverage, losing Medicaid, or a plan leaving your area all count. The window is usually two or three months, so tell someone early.
See also: Special Enrollment Period, Creditable coverage
Permission from your main doctor to see a specialist.
Why it matters. Original Medicare never requires one. Most HMO Advantage plans do. It is one of the practical differences you will feel every year.
See also: HMO, PPO, Original Medicare
Short-term nursing or rehabilitation in a facility after a hospital stay.
Why it matters. Medicare covers up to 100 days per benefit period, but only after a three-day inpatient hospital stay, and days 21 to 100 carry a daily charge. Observation days do not count toward the three.
See also: Observation status, Benefit period, Part A
A window outside the usual dates, opened by a specific event in your life.
Why it matters. The big one: when employer coverage ends, you get eight months to take Part B without penalty, but only 63 days to pick up drug coverage. Those two clocks are different lengths and people get caught by it.
See also: Qualifying life event, Creditable coverage, Annual Enrollment Period, General Enrollment Period
A one to five score Medicare publishes each fall for every Medicare Advantage and drug plan.
Why it matters. It measures things like how often members get their prescriptions, how quickly complaints are handled, and how people rate the plan. A five-star plan can also be joined outside the usual dates.
See also: Medicare Advantage, Part D
The band a drug sits in on a plan formulary. Lower tiers cost you less.
Why it matters. The same medication can be tier 2 on one plan and tier 4 on another. That single difference can be worth more than the plan premium.
A one-time preventive visit available in your first twelve months on Part B.
Why it matters. It costs nothing and sets a baseline. After the first year it becomes the annual wellness visit, which is also free.
See also: Preventive services, Part B
No term matches that. Try a shorter word, or call us on (419) 555-0142 and we will explain it.
That is our failure, not yours. Call and tell us which one, and we will explain it properly and then rewrite the entry.