Medicare basics
Four parts, one system — here's what each one covers.
Medicare can feel like an alphabet soup of letters. This guide breaks down Parts A, B, C, and D, the biggest decision most people face (Original Medicare vs. Medicare Advantage), and what's generally not covered.
Medicare is a U.S. federal program with no direct Canadian equivalent. Looking for Canadian public coverage instead? See how Canadian coverage works →
Show me the four parts ↓Parts A, B, C, and D
Each part covers a different category of care — you may use some, all, or none depending on how you enroll.
Part A
Covers inpatient hospital stays, skilled nursing facility care, hospice, and some home health care.
Many people qualify for premium-free Part A based on work history.
Part B
Covers doctor visits, outpatient care, preventive services, and durable medical equipment.
Generally requires an ongoing monthly premium.
Part C
Private plans approved by Medicare that bundle Part A and B — often Part D too — sometimes with extra benefits.
An alternative way to receive your Medicare benefits, not an add-on to Original Medicare.
Part D
Private plans that help cover the cost of prescription medications.
Each plan has its own list of covered drugs — worth checking before enrolling.
Original Medicare vs. Medicare Advantage
This choice shapes nearly everything else about your coverage.
- Generally see any provider who accepts Medicare, nationwide
- Often paired with a separate Part D plan
- Many people add a supplemental (Medigap) policy to help with gaps
- Often uses a network, similar to private employer plans
- May include extra benefits like dental or vision
- Typically includes an annual out-of-pocket maximum
There's no universal right answer
The right choice depends on your health needs, budget, and preference for provider flexibility versus bundled extras — this is worth comparing carefully each year during open enrollment.
What Medicare generally doesn't cover
Original Medicare has notable gaps — many people plan around these with supplemental coverage or a Medicare Advantage plan.
Enrollment periods, in brief
Specific dates and penalty rules can change — treat this as an overview, and confirm current details at Medicare.gov.
Initial Enrollment Period
A window around when you first become eligible, typically tied to turning 65.
Annual Open Enrollment
A yearly window in the fall when you can review and change your coverage.
Special Enrollment Periods
Available in specific circumstances, like losing other coverage.
General Enrollment Period
A window for those who missed their initial enrollment, sometimes with a late penalty.
Enrollment timing can affect your cost
Missing certain windows can lead to a lasting premium penalty in some cases — if you're approaching eligibility, it's worth confirming your specific timeline well in advance.
What are you trying to do?
Compare Medicare Advantage plans
Understand a Medicare denial
Check if a service is covered
Read the guide →Understand a medical bill
Read the guide →Appeal a coverage decision
Read the guide →Resolve an insurance problem
Browse the Hub →Common questions about Medicare
Do I need all four parts?
Not necessarily — many people use Original Medicare (A and B) with a separate Part D plan, while others choose a Medicare Advantage (Part C) plan instead, which often includes drug coverage.
What's a Medicare Summary Notice?
It's Original Medicare's version of an EOB — a statement showing what was billed and what Medicare paid. Like an EOB, it's generally not a bill itself.
Can I switch between Original Medicare and Medicare Advantage?
Generally yes, during specific enrollment periods — though switching back and forth may have its own rules worth checking in advance.
What is Medigap?
A supplemental insurance policy some people add to Original Medicare to help cover certain out-of-pocket costs it doesn't pay for.
Know your parts. Know your next step.
Understanding the basics is the first step toward a coverage choice that actually fits your needs.