Medicare terms, in plain English.
Every definition written at an 8th-grade reading level. Search a term or scan the list.
- AEP
- Annual Enrollment Period. October 15 – December 7 each year. You can join, switch, or drop Medicare Advantage and Part D plans.
- Advantage (Part C)
- A Medicare plan offered by a private insurer that bundles Parts A, B, and usually D. Uses a network of providers.
- ANOC
- Annual Notice of Change. A document your Advantage or Part D plan mails you in September detailing changes for the coming year.
- Appeal
- A formal request to Medicare or your plan to review a coverage decision you disagree with.
- Assignment
- When a provider agrees to accept the Medicare-approved amount as full payment.
- Coinsurance
- The percentage of costs you pay after meeting your deductible — commonly 20% under Original Medicare.
- Copay
- A fixed dollar amount you pay for a covered service, like $20 for a doctor visit.
- Creditable Coverage
- Health or drug coverage at least as good as Medicare's. Keeping it lets you delay Medicare enrollment without penalty.
- Deductible
- The amount you pay out of pocket each year before Medicare or your plan begins to pay.
- Donut Hole
- A former coverage gap in Part D. Eliminated in 2025 — Part D now has a $2,000 annual out-of-pocket cap.
- Dual Eligible
- Someone who qualifies for both Medicare and Medicaid.
- Extra Help
- A federal program that helps people with limited income pay for Part D premiums and copays.
- Formulary
- The list of drugs a Part D or Advantage plan covers.
- GEP
- General Enrollment Period. January 1 – March 31 each year, for people who missed their initial enrollment.
- Guaranteed Issue
- Times when insurers must sell you a Medigap policy regardless of your health, such as the 6 months after your Part B begins.
- HMO
- Health Maintenance Organization. An Advantage plan type that requires you to use in-network providers and get referrals.
- IEP
- Initial Enrollment Period. The 7-month window around your 65th birthday to sign up for Medicare.
- IRMAA
- Income-Related Monthly Adjustment Amount. Extra Part B and D premiums for higher-income beneficiaries.
- MA OEP
- Medicare Advantage Open Enrollment Period. January 1 – March 31. Advantage members can switch or drop.
- Medigap
- Medicare Supplement Insurance. Private policies that pay what Original Medicare doesn't.
- MSP
- Medicare Savings Program. State-run programs that help pay Medicare premiums and cost-sharing.
- Network
- The providers, hospitals, and pharmacies that contract with an Advantage or Part D plan.
- Original Medicare
- Parts A and B, run directly by the federal government. No networks.
- Part A
- Hospital insurance. Covers inpatient stays, skilled nursing, hospice, and some home health.
- Part B
- Medical insurance. Covers doctor visits, outpatient care, and preventive services.
- Part C
- Medicare Advantage — see Advantage.
- Part D
- Prescription drug coverage offered through private insurers.
- PPO
- Preferred Provider Organization. An Advantage plan type with more flexibility to see out-of-network providers, at higher cost.
- Premium
- The amount you pay each month for Medicare or a Medicare plan.
- SEP
- Special Enrollment Period. Triggered by life events like losing employer coverage or moving.
- Cash-pay patient
- A patient who pays the provider directly at a transparent price instead of going through an insurance claim — often far cheaper.
- ICHRA
- Individual Coverage Health Reimbursement Arrangement. An employer gives tax-free dollars to buy an individual health plan. ICHRA dollars can't buy a cost-sharing membership.
- Need
- In medical cost sharing, the eligible expenses from a single injury or illness that exceed your IUA.
- Parallel healthcare economy
- Direct primary care, medical cost sharing, cash-pay surgery centers and similar options where patients pay providers directly, skipping middlemen.
- Direct Access Care
- A monthly membership (not insurance) giving access to everyday services like 24/7 virtual care, labs and prescription savings.
- Health Care Sharing
- Also called medical cost sharing. Members contribute monthly and share each other's large, eligible medical bills. Not insurance.
- IUA
- Initial Unshareable Amount. In medical cost sharing, the portion of each medical need you pay before the community shares the rest — similar to a deductible.
- Needs Coordinator
- A real person at a sharing program who guides you through submitting a medical bill (a 'need') and getting it shared.
- Out-of-network
- A provider outside a plan's network. Many sharing programs have no network, so you can see any provider.
- SSA-44
- The form used to request an IRMAA reduction after a life-changing event like retirement.
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