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Reviewed for accuracy by Lauri Middleton, RN, MSN, licensed Medicare agentReviewed for clarity by Karen OrillaMeet our reviewers →
Glossary
Plain words for the letters
Every term used on this site, in the order a first-timer meets them.
The parts
- Part A
- Hospital insurance: inpatient stays, skilled nursing after a hospital stay, hospice and some home health. Most people pay no monthly premium for it.
- Part B
- Medical insurance: doctor visits, outpatient care, tests, preventive services and equipment. It has a monthly premium, and this is the part the enrollment windows and penalties are mostly about.
- Part C (Medicare Advantage)
- A private plan that bundles Part A and Part B, usually drug coverage, and often extras, into one card with a network and a yearly cap on what you pay for medical care.
- Part D
- Prescription drug coverage from a private plan — either a separate plan added to Original Medicare or built into a Medicare Advantage plan.
Windows and dates
- Initial Enrollment Period
- Your first, seven-month window around the month you turn 65.
- Special Enrollment Period
- A window that opens because of a life event — most commonly, leaving coverage from a current job.
- General Enrollment Period
- January 1 to March 31 each year: the fallback window for Part B when the others have passed.
- Open Enrollment (October 15 – December 7)
- The yearly window to join, switch or drop Medicare Advantage and Part D plans for the next year.
- Medigap open enrollment
- The six months from when you are 65 and have Part B, when Medigap must be sold to you without health questions.
- Annual Notice of Change
- The letter a plan sends each fall listing what changes on January 1 — premiums, copays, the drug list, the network. Read it before Open Enrollment.
What you pay
- Creditable coverage
- Drug coverage that is at least as good as standard Part D. Having it means no Part D penalty clock is running. Employers must tell you in writing whether theirs is creditable.
- Deductible
- What you pay for care before the coverage starts paying its share.
- Coinsurance and copays
- Your share of each service: a percentage (coinsurance, like Part B's 20 %) or a flat amount (copay, like $40 for a specialist).
- Yearly cap (out-of-pocket maximum)
- The most a Medicare Advantage plan can make you pay for covered medical care in a year. Original Medicare has no cap on its own.
- Late enrollment penalty
- An amount added to a premium for signing up later than your windows allowed. Part B's is 10 % per full year and lasts as long as Part B; Part D's is 1 % of the base premium per month and is permanent.
- Income-related adjustment (IRMAA)
- Higher Part B and Part D premiums for people whose income two years ago was above a threshold. Social Security decides it and there is an appeal for a drop in income.
- Who pays first
- When you have Medicare and another plan, one of them pays first and the other second. With a current job at an employer of 20 or more, the job plan pays first; under 20, Medicare pays first.
- Health Savings Account (HSA)
- A tax-advantaged account paired with a high-deductible job plan. You can keep and spend it after Medicare, but contributions must stop before Part A starts.
Kinds of coverage
- Original Medicare
- Part A and Part B run by the federal government. Any doctor in the U.S. who accepts Medicare; you pay 20 % of most Part B services with no yearly cap unless you add Medigap.
- Medigap (Medicare Supplement)
- A private policy that pays some or most of the 20 % and other gaps in Original Medicare. Plans are standardized by letter (G, N and so on). It cannot be used with Medicare Advantage.
- Network
- The doctors, hospitals and pharmacies a plan has contracts with. HMO plans generally cover only the network; PPO plans cover outside it at a higher cost.
- COBRA
- Continuing a job plan for a while after leaving the job, at your own cost. It is not coverage from a current job, so it does not delay the Part B clock.
People and programs
- "Welcome to Medicare" visit
- A one-time preventive visit covered in the first 12 months of Part B: a review of your health, risks and a plan for the screenings you are due.
- Social Security (SSA)
- The agency you sign up for Part A and Part B through, and where you apply for Extra Help. 1-800-772-1213 or ssa.gov/medicare.
- SHIP counselor
- State Health Insurance Assistance Programs give free, confidential Medicare counseling in every state. Find yours at shiphelp.org.
- Extra Help
- A Social Security program that lowers Part D premiums, deductibles and copays for people with limited income and resources.
- Medicare Savings Programs
- State-run programs that pay the Part B premium, and sometimes deductibles and copays, for people with limited income. Applied for through the state Medicaid office.