Plain definitions
Medicare glossary — in plain English.
A short glossary of the Medicare and senior-coverage terms you actually hear when comparing plans.
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A–G
- AEP (Annual Enrollment Period)
- October 15 to December 7. The main window to switch plans. More.
- Coinsurance
- Your share of cost as a percentage (often 20%).
- Copay
- A flat fee per service.
- Coverage gap (donut hole)
- Historical Part D phase where you paid more for drugs.
- Creditable coverage
- Other coverage at least as good as Medicare — keeps you out of late penalties. More.
- Deductible
- Amount you pay before coverage starts.
- Extra Help
- Low Income Subsidy for prescription drugs. More.
- Formulary
- The list of drugs your Part D plan covers, organized by tier.
H–O
- HMO (Health Maintenance Organization)
- A network plan that usually requires you to stay in network.
- IEP (Initial Enrollment Period)
- The 7 months around your 65th birthday. More.
- IRMAA
- Income-Related Monthly Adjustment Amount — a surcharge on Part B and D for higher-income enrollees. More.
- MA OEP
- Medicare Advantage Open Enrollment Period — January 1 to March 31. More.
- Medigap
- Medicare Supplement Insurance. Pays your share of Original Medicare cost.
P–Z
- Part A
- Hospital insurance.
- Part B
- Outpatient and doctor insurance.
- Part C
- Medicare Advantage.
- Part D
- Prescription drug coverage.
- PPO (Preferred Provider Organization)
- A network plan that allows out-of-network care at higher cost.
- Prior authorization
- Plan approval required before certain services.
- SEP (Special Enrollment Period)
- A window triggered by qualifying life events.
- SNP (Special Needs Plan)
- An Advantage plan for specific conditions, dual eligibility, or institutional needs.
- Tier
- The cost category a drug falls into on a formulary.