Medicare A–Z

Medicare A–Z explains the words you will meet in Medicare letters, plan materials and enrollment forms, in plain English and based on official sources such as Medicare.gov, CMS and the Social Security Administration. This site is independent and not affiliated with Medicare, CMS or any government agency, and it never recommends or ranks plans or insurers; everything here is general information, not insurance, financial, tax, legal or medical advice. For help with your own situation, contact your State Health Insurance Assistance Program (SHIP) for free counseling, your state insurance department, or 1-800-MEDICARE.

Annual Notice of Change (ANOC): A notice from your Medicare Advantage or drug plan listing changes in coverage, costs and other details that take effect in January. The Medicare & You 2027 handbook says plans send it by September 30, so you can review it before fall Open Enrollment.; Related:Open Enrollment (fall)Medicare Advantage (Part C)Formulary
Assignment: An agreement by a doctor, other provider or supplier to be paid directly by Medicare, accept the Medicare-approved amount as payment in full, and not bill you more than the Medicare deductible and coinsurance. In Original Medicare, using providers who accept assignment generally keeps your costs lower.; Related:Medicare-approved amount Excess charge Original Medicare
Benefit period: The way Original Medicare measures your use of hospital and skilled nursing facility care. It starts the day you are admitted as an inpatient and ends after 60 days in a row without inpatient hospital or skilled nursing facility care; you pay the Part A inpatient deductible for each benefit period, and there is no limit on how many you can have. After day 90 of a hospital stay you can draw on 60 lifetime reserve days; CMS lists their coinsurance at $868 a day for 2026.; Related:Medicare Part A (Hospital Insurance)Skilled nursing facility (SNF) care Deductible
COBRA: Continuation coverage you may be able to keep for a time after a job ends. The Medicare & You 2027 handbook warns that COBRA does not count as coverage based on current employment, so it generally does not give you a Special Enrollment Period to sign up for Part B when it ends, and it may pay only a small share of costs once you are eligible for Medicare.; Related:Special Enrollment Period (SEP)Part B late enrollment penalty Primary payer and secondary payer
Coinsurance: Your share of the cost of a covered service after any deductible, usually stated as a percentage. In Original Medicare you typically pay 20% of the Medicare-approved amount for most Part B services, with no yearly out-of-pocket limit unless you have supplemental coverage.; Related:Copayment Deductible Medicare-approved amount
Copayment: A fixed dollar amount you pay as your share of the cost of a covered service or prescription, such as a set charge for an office visit, after any deductible. Many Medicare Advantage and Part D plans use copayments for some services or drugs, and amounts vary by plan.; Related:Coinsurance Deductible Formulary
Creditable prescription drug coverage: Drug coverage expected to pay, on average, at least as much as standard Medicare drug coverage, such as some employer, union, TRICARE, VA or Indian Health Service coverage. Your plan must tell you each year whether it is creditable; keeping it can protect you from the Part D late enrollment penalty if you join a Medicare drug plan later.; Related:Part D late enrollment penalty Medicare Part D (drug coverage)TRICARE For Life
Custodial care (long-term care): Help with everyday personal tasks such as bathing, dressing and using the bathroom, often for people with a chronic illness or disability. Medicare.gov says Medicare and most health insurance, including Medigap, don't pay for this kind of long-term care; Medicaid (if you qualify) or private long-term care insurance may help.; Related:Skilled nursing facility (SNF) care Medicaid Medigap (Medicare Supplement Insurance)
Deductible: The amount you pay for covered care or prescriptions before Original Medicare, your plan or other insurance starts to pay. For 2026, CMS lists the Part B deductible at $283 a year and the Part A inpatient hospital deductible at $1,736 per benefit period.; Related:Coinsurance Benefit period Premium
Dual eligible: A person who qualifies for both Medicare and Medicaid. Medicare's handbook notes that most health care costs are covered for people who qualify for both, and people with full Medicaid coverage automatically qualify for Extra Help with drug costs; some can choose a Dual Eligible Special Needs Plan.; Related:Medicaid Extra Help (Low-Income Subsidy)Special Needs Plan (SNP)
End-Stage Renal Disease (ESRD): Permanent kidney failure that requires a regular course of dialysis or a kidney transplant, which can make you eligible for Medicare before age 65. Special rules apply: for example, the Medicare & You 2027 handbook says that with employer group health coverage, the employer plan pays first for the first 30 months of Medicare eligibility.; Related:Medicare Primary payer and secondary payer Special Enrollment Period (SEP)
Excess charge: In Original Medicare, the difference between what a provider who does not accept assignment is legally allowed to charge and the Medicare-approved amount. The Medicare & You 2027 handbook says that in many cases the charge cannot be more than 15% above the approved amount; some Medigap plans cover excess charges.; Related:Assignment Medicare-approved amount Medigap (Medicare Supplement Insurance)
Extra Help (Low-Income Subsidy): A Medicare program that helps people with limited income and resources pay Part D costs such as premiums, deductibles and coinsurance; people who get it do not pay a Part D late enrollment penalty. For 2026, the Medicare & You 2027 handbook lists income limits of less than $23,940 a year for a single person and less than $32,460 for a married couple living together, with resource limits of $18,090 and $36,100; apply through Social Security.; Related:Medicare Part D (drug coverage)Medicare Savings Programs (MSPs)Dual eligible
Formulary: A plan's list of covered prescription drugs, also called a drug list. Drugs are usually grouped into cost levels called tiers, and plans can change formularies during the year but must notify you of changes that affect drugs you take.; Related:Medicare Part D (drug coverage)Prior authorization Annual Notice of Change (ANOC)
General Enrollment Period (GEP): January 1 through March 31 each year, when you can sign up for Part B (or buy Part A) if you missed your Initial Enrollment Period and do not qualify for a Special Enrollment Period. Coverage starts the first day of the month after you sign up, and you may owe a late enrollment penalty.; Related:Initial Enrollment Period (IEP)Special Enrollment Period (SEP)Part B late enrollment penalty
Guaranteed issue rights: Situations in which federal law requires insurers to sell or offer you a Medigap policy without denying you, excluding pre-existing conditions or charging more for health problems. Examples include losing certain coverage through no fault of your own and the "trial right" to leave a Medicare Advantage Plan in your first year; you generally have 63 days after the old coverage ends to apply, and states may add more rights.; Related:Medigap (Medicare Supplement Insurance)Medigap Open Enrollment Period Medical underwriting
Health Maintenance Organization (HMO) plan: A type of Medicare Advantage Plan that generally requires you to use doctors and hospitals in its network, except for emergency care, out-of-area urgent care and temporary out-of-area dialysis. In most cases you choose a primary care doctor and need a referral to see a specialist.; Related:Preferred Provider Organization (PPO) plan Medicare Advantage (Part C)Special Needs Plan (SNP)
Hospice care: Care focused on comfort and symptom management for people with a terminal illness, covered under Part A. Medicare.gov says your hospice doctor and regular doctor (if you have one) must certify a life expectancy of 6 months or less.; Related:Medicare Part A (Hospital Insurance)Original Medicare Custodial care (long-term care)
Income-Related Monthly Adjustment Amount (IRMAA): An extra charge added to Part B and Part D premiums for people with higher incomes, based on the modified adjusted gross income on your tax return from two years earlier. For 2026, the Medicare & You 2027 handbook says you may pay IRMAA if your 2024 modified adjusted gross income was above $109,000 (individual return) or $218,000 (joint return); if a qualifying life-changing event lowered your income, you can ask Social Security to reduce it.; Related:Premium Medicare Part B (Medical Insurance)Medicare Part D (drug coverage)
Initial Enrollment Period (IEP): Your first chance to sign up for Part A and Part B: generally a 7-month window that starts 3 months before the month you turn 65 and ends 3 months after it. Signing up in the first 3 months usually means coverage starts the first day of your birthday month; people already getting Social Security benefits are typically enrolled automatically.; Related:General Enrollment Period (GEP)Special Enrollment Period (SEP)Part B late enrollment penalty
Medicaid: A joint federal and state program that helps with medical costs for some people with limited income and, in some cases, limited resources. Rules vary by state, and Medicare.gov notes Medicaid offers benefits such as nursing facility services and help paying Medicare premiums and other costs.; Related:Dual eligible Medicare Savings Programs (MSPs)Custodial care (long-term care)
Medical identity theft: When someone uses your personal information, such as your name, Social Security Number or 11-character Medicare Number, to submit fraudulent claims. Medicare's handbook advises giving your Medicare Number only to your providers, insurers and their licensed agents, plans acting for you or state assistance programs, and not to anyone who contacts you by phone, email or in person unless you gave permission in advance; check your statements and report suspected fraud to 1-800-MEDICARE or your Senior Medicare Patrol.; Related:Senior Medicare Patrol (SMP)Medicare Summary Notice (MSN)State Health Insurance Assistance Program (SHIP)
Medical underwriting: The process an insurer uses to decide, based on your medical history, whether to accept your application, whether to add a waiting period for pre-existing conditions (where state law allows), and how much to charge. Outside your Medigap Open Enrollment Period and guaranteed issue situations, a Medigap policy may be harder to get or cost more because of it.; Related:Medigap (Medicare Supplement Insurance)Medigap Open Enrollment Period Guaranteed issue rights
Medicare: The federal health insurance program for people 65 and older and some younger people with certain disabilities or conditions, including End-Stage Renal Disease and ALS. It has four parts (A, B, C and D) and, unlike many private plans, does not offer family or couple coverage: each person enrolls individually.; Related:Original Medicare Medicare Advantage (Part C)Medicaid
Medicare Advantage (Part C): A Medicare-approved plan from a private company that bundles Part A and Part B benefits and usually Part D drug coverage. Plans may use networks, referrals and prior authorization, have a yearly limit on out-of-pocket costs for Part A and Part B services, and often add extras such as vision, hearing or dental; you still pay the Part B premium, and you cannot use a Medigap policy with one.; Related:Original Medicare Health Maintenance Organization (HMO) plan Preferred Provider Organization (PPO) plan
Medicare Advantage Open Enrollment Period: January 1 through March 31 each year, when people already in a Medicare Advantage Plan can make one change: switch to another Medicare Advantage Plan, or drop it for Original Medicare and join a separate drug plan. It cannot be used to move from Original Medicare into Medicare Advantage.; Related:Open Enrollment (fall)Medicare Advantage (Part C)Original Medicare
Medicare Part A (Hospital Insurance): The part of Original Medicare that helps cover inpatient hospital care, skilled nursing facility care, hospice and some home health care. Most people pay no Part A premium; for 2026, CMS lists the inpatient hospital deductible at $1,736 per benefit period and coinsurance of $434 a day for days 61 through 90.; Related:Premium-free Part A Benefit period Medicare Part B (Medical Insurance)
Medicare Part B (Medical Insurance): The part of Original Medicare that helps cover doctors' services, outpatient care, durable medical equipment such as walkers and hospital beds, and many preventive services. For 2026, CMS lists the standard monthly premium at $202.90 and the yearly deductible at $283, after which you typically pay 20% of the Medicare-approved amount.; Related:Medicare Part A (Hospital Insurance)Income-Related Monthly Adjustment Amount (IRMAA)Preventive services
Medicare Part D (drug coverage): Prescription drug coverage offered by private companies that follow Medicare's rules, either as a separate drug plan added to Original Medicare or included in most Medicare Advantage Plans. Medicare.gov says no drug plan may have a deductible above $615 in 2026 ($700 in 2027); premiums and covered drugs vary by plan.; Related:Formulary Part D out-of-pocket limit Part D late enrollment penalty
Medicare Prescription Payment Plan: A payment option offered by all Part D plans that spreads your out-of-pocket drug costs into monthly payments across the calendar year. The Medicare & You 2027 handbook notes it does not lower your drug costs and may not suit you if you get or qualify for Extra Help.; Related:Medicare Part D (drug coverage)Part D out-of-pocket limit Extra Help (Low-Income Subsidy)
Medicare Savings Programs (MSPs): State-run programs that help people with limited income and resources pay Medicare costs. There are four: Qualified Medicare Beneficiary (QMB), Specified Low-Income Medicare Beneficiary (SLMB), Qualifying Individual (QI) and Qualified Disabled and Working Individuals (QDWI); you apply through your state Medicaid office, and qualifying for QMB, SLMB or QI also gets you Extra Help automatically.; Related:Qualified Medicare Beneficiary (QMB) program Extra Help (Low-Income Subsidy)Medicaid
Medicare Summary Notice (MSN): A statement for people with Original Medicare that lists services billed to Medicare, what Medicare paid and what you may owe; it is not a bill. Reviewing it helps you spot errors or fraud, and it explains how to appeal a coverage decision.; Related:Medical identity theft Original Medicare Senior Medicare Patrol (SMP)
Medicare-approved amount: The payment amount Original Medicare sets for a covered service or item. Medicare pays its share and you pay yours, such as 20% coinsurance after the Part B deductible.; Related:Assignment Excess charge Coinsurance
Medigap (Medicare Supplement Insurance): Private insurance that helps pay your share of costs in Original Medicare, such as coinsurance and deductibles. Policies are standardized and, in most states, named by letters such as Plan G or Plan K, with the same benefits for each letter no matter which company sells it; Medigap works only with Original Medicare, not Medicare Advantage.; Related:Medigap Open Enrollment Period Guaranteed issue rights Original Medicare
Medigap Open Enrollment Period: A one-time, 6-month period that starts the first month you are both 65 or older and enrolled in Part B. During it, federal law lets you buy any Medigap policy sold in your state without being denied or charged more because of health problems; afterward you may face medical underwriting.; Related:Medigap (Medicare Supplement Insurance)Medical underwriting Guaranteed issue rights
Observation services: Hospital outpatient services you get while your doctor decides whether to admit you as an inpatient or send you home. Medicare.gov notes you can be an outpatient even if you stay overnight, and observation time does not count toward the 3 inpatient days needed for Part A skilled nursing facility coverage, so it is worth asking about your status.; Related:Skilled nursing facility (SNF) care Medicare Part A (Hospital Insurance)Medicare Part B (Medical Insurance)
Open Enrollment (fall): October 15 through December 7 each year, when anyone with Medicare can join, switch or drop a Medicare Advantage or Part D plan, or move between Original Medicare and Medicare Advantage. Changes take effect January 1. It is sometimes called the Annual Enrollment Period (AEP), though Medicare's own materials say Open Enrollment, and the FTC warns that health insurance scams pick up during Open Enrollment.; Related:Medicare Advantage Open Enrollment Period Annual Notice of Change (ANOC)State Health Insurance Assistance Program (SHIP)
Original Medicare: The fee-for-service program made up of Part A (Hospital Insurance) and Part B (Medical Insurance). You can use any doctor or hospital in the U.S. that takes Medicare, generally without referrals, and can add a separate drug plan and a Medigap policy; on its own it has no yearly out-of-pocket limit.; Related:Medicare Advantage (Part C)Medigap (Medicare Supplement Insurance)Assignment
Part B late enrollment penalty: A lifelong increase in your Part B premium if you don't sign up when first eligible and don't qualify for a Special Enrollment Period. The Medicare & You 2027 handbook says the premium may go up 10% for each full 12-month period you could have had Part B but didn't; enrolling in a Medicare Savings Program may remove it.; Related:Initial Enrollment Period (IEP)Special Enrollment Period (SEP)General Enrollment Period (GEP)
Part D late enrollment penalty: An amount permanently added to your Part D premium if, after your Initial Enrollment Period, you go 63 or more days in a row without Part D or other creditable drug coverage. The Medicare & You 2027 handbook says it is 1% of the national base beneficiary premium ($38.99 in 2026) for each full uncovered month; people with Extra Help don't pay it.; Related:Creditable prescription drug coverage Medicare Part D (drug coverage)Extra Help (Low-Income Subsidy)
Part D out-of-pocket limit: A yearly cap on what you pay for covered Part D drugs. Medicare.gov lists the cap at $2,100 for 2026 and $2,400 for 2027; once you (or programs like Extra Help on your behalf) reach it, you pay $0 for covered Part D drugs for the rest of the year.; Related:Medicare Part D (drug coverage)Medicare Prescription Payment Plan Extra Help (Low-Income Subsidy)
Preferred Provider Organization (PPO) plan: A type of Medicare Advantage Plan with a network of doctors and hospitals that also lets you use out-of-network providers for covered services, usually at a higher cost. Rules on referrals, drug coverage and costs vary by plan.; Related:Health Maintenance Organization (HMO) plan Medicare Advantage (Part C)Special Needs Plan (SNP)
Premium: The regular payment you make to Medicare, an insurance company or a plan for health or drug coverage. In Medicare you may pay several, such as the Part B premium plus a Medicare Advantage, Part D or Medigap premium.; Related:Deductible Income-Related Monthly Adjustment Amount (IRMAA)Premium-free Part A
Premium-free Part A: Part A with no monthly premium, which you usually get if you or your spouse paid Medicare taxes long enough; CMS says this means at least 40 quarters of covered work. For 2026, CMS lists the Part A buy-in premium at $311 or $565 a month for those without enough work history, and anyone who must buy Part A and delays may owe a 10% higher premium for twice the number of years they waited.; Related:Medicare Part A (Hospital Insurance)Premium Qualified Medicare Beneficiary (QMB) program
Preventive services: Care meant to prevent illness or find it early, such as screenings, vaccines and the yearly wellness visit. Under Part B you pay nothing for most covered preventive services if your provider accepts assignment, though some services can carry costs.; Related:Medicare Part B (Medical Insurance)Assignment Original Medicare
Primary payer and secondary payer: When you have Medicare and other insurance, the primary payer pays first up to its limits and the secondary payer pays only for remaining covered costs. For example, the Medicare & You 2027 handbook says that if you're 65 or older with coverage from a current employer with 20 or more employees, the employer plan pays first; with retiree coverage or Medicaid, Medicare pays first.; Related:COBRA TRICARE For Life VA health care and Medicare
Prior authorization: Approval you or your provider must get from a plan before it will cover certain services, supplies or drugs. Medicare Advantage and Part D plans can require it, along with related rules such as step therapy (trying a lower-cost drug first) and quantity limits; Original Medicare generally does not.; Related:Medicare Advantage (Part C)Formulary Medicare Part D (drug coverage)
Qualified Medicare Beneficiary (QMB) program: The Medicare Savings Program that helps pay Part A premiums (if you owe them) and Part B premiums. Medicare providers are not allowed to bill people in QMB for Medicare deductibles, coinsurance or copayments for covered services, and you can call 1-800-MEDICARE to confirm your QMB status if you are billed.; Related:Medicare Savings Programs (MSPs)Medicaid Dual eligible
Senior Medicare Patrol (SMP): Federally funded programs, supported by the Administration for Community Living, that help people with Medicare prevent, detect and report health care fraud, errors and abuse. Contact your state's SMP if you see unfamiliar charges or get suspicious calls or offers about your Medicare card.; Related:Medical identity theft State Health Insurance Assistance Program (SHIP)Medicare Summary Notice (MSN)
Skilled nursing facility (SNF) care: Daily skilled nursing or therapy in a nursing facility, covered by Part A after a qualifying inpatient hospital stay of at least 3 days in a row. For 2026, CMS lists coinsurance of $217 a day for days 21 through 100 in a benefit period; it is different from custodial long-term care, which Medicare does not cover.; Related:Benefit period Observation services Custodial care (long-term care)
Special Enrollment Period (SEP): A chance to sign up or change coverage outside the usual windows because of certain life events. For example, if you delayed Part B because of job-based coverage from current work, the Medicare & You 2027 handbook says you can sign up while covered or within 8 months after the job or coverage ends, whichever comes first, usually without a penalty.; Related:Initial Enrollment Period (IEP)COBRA Part B late enrollment penalty
Special Needs Plan (SNP): A Medicare Advantage Plan for specific groups: people with both Medicare and Medicaid (D-SNP), people with certain severe or chronic conditions (C-SNP), or people who need an institutional level of care (I-SNP). SNPs are HMO or PPO types that tailor benefits, providers and drug lists to their members, and you must keep meeting the plan's eligibility rules to stay enrolled.; Related:Medicare Advantage (Part C)Dual eligible Health Maintenance Organization (HMO) plan
State Health Insurance Assistance Program (SHIP): A national network of state programs, funded by the federal government, that offers free one-on-one Medicare counseling; the Medicare & You 2027 handbook notes that SHIPs aren't connected to any insurance company or health plan. SHIP counselors can help you compare plans, understand enrollment rules and apply for programs such as Extra Help and Medicare Savings Programs.; Related:Senior Medicare Patrol (SMP)Medicare Savings Programs (MSPs)Extra Help (Low-Income Subsidy)
TRICARE For Life: Medicare-wraparound coverage for TRICARE-eligible people who have both Medicare Part A and Part B, regardless of age or where they live. TRICARE says coverage is automatic once you have Parts A and B and doesn't extend to family members, so you need to keep both parts to keep it.; Related:Primary payer and secondary payer Creditable prescription drug coverage VA health care and Medicare
VA health care and Medicare: Veterans can have both VA health care and Medicare and choose which to use each time they get care: VA generally covers care at VA facilities or care it authorizes, while Medicare can cover care from non-VA providers, and VA doesn't bill Medicare. VA encourages signing up for Medicare when eligible, and the Medicare & You 2027 handbook notes VA coverage doesn't give you a Special Enrollment Period for Part B later.; Related:TRICARE For Life Creditable prescription drug coverage Part B late enrollment penalty