Medicare has four main parts — plus optional add-ons
Medicare is the federal health program for people 65 and older and for some younger people with disabilities. Coverage is organized into parts, each covering different kinds of care. Most people start with Original Medicare (Part A and Part B). You can then add Part D drug coverage, Medigap supplemental insurance, or choose Medicare Advantage (Part C) as an alternative way to receive your benefits.
This article explains what each part generally covers. Costs, plan availability, and rules can vary by location and year — always confirm details with official sources before making coverage decisions.
Original Medicare: Part A and Part B
Original Medicare (sometimes called Traditional or fee-for-service Medicare) is run by the federal government. Unless you actively choose a different path, you receive benefits through Part A and Part B.
- Part A focuses on hospital and facility-based care.
- Part B focuses on medical services you receive outside the hospital.
You can see any doctor or hospital that accepts Medicare, anywhere in the country. Original Medicare does not cap your annual out-of-pocket costs on its own, which is why many people add supplemental coverage.
Part A — Hospital Insurance
Part A helps pay for care when you are admitted to a hospital or need certain facility-based services. It generally includes:
- Inpatient hospital stays (room, meals, nursing care, and related services)
- Skilled nursing facility care after a qualifying hospital stay (not long-term custodial care)
- Hospice care for terminal illness
- Some home health services when you meet Medicare's requirements
Most people qualify for premium-free Part A if they or a spouse paid Medicare taxes through work for about 10 years. If you do not qualify, you may be able to buy Part A. Part A has deductibles and coinsurance for hospital and skilled nursing stays — you may still owe a share of the cost even when Part A applies.
Part B — Medical Insurance
Part B helps pay for medically necessary services and preventive care outside the hospital. It generally includes:
- Doctor visits and other health care provider services
- Outpatient care (clinics, same-day surgery centers, and similar settings)
- Durable medical equipment (wheelchairs, walkers, hospital beds, and similar items)
- Many preventive services (screenings, vaccines, and annual wellness visits)
- Some home health care that Part A does not cover
Part B requires a monthly premium for most people. You also pay an annual deductible and typically 20% coinsurance for many covered services after the deductible is met. Part B premiums can be higher if your income is above certain thresholds (IRMAA).
Part C — Medicare Advantage
Medicare Advantage (Part C) is not a separate benefit on top of Original Medicare — it is an alternative way to receive your Medicare benefits. Private insurance companies offer Medicare Advantage plans that Medicare approves.
These plans must cover everything Original Medicare covers, but they can use different cost-sharing, networks, and prior-authorization rules. Most Medicare Advantage plans bundle Part A, Part B, and usually Part D into one plan. Many also include extra benefits Original Medicare does not cover, such as routine dental, vision, or hearing services.
If you join a Medicare Advantage plan, you still have Medicare — but you receive your hospital and medical benefits through the plan, not through Original Medicare. You generally cannot use Medigap with Medicare Advantage at the same time.
Part D — Prescription Drug Coverage
Part D helps pay for outpatient prescription drugs. Part D plans are offered by private insurers that follow Medicare rules.
You can get drug coverage in two main ways:
- Add a standalone Part D plan to Original Medicare (Parts A and B).
- Join a Medicare Advantage plan that includes drug coverage (often called an MA-PD plan).
Each Part D plan has its own formulary (list of covered drugs), cost-sharing tiers, and pharmacy network. Plans can change their formularies each year, so reviewing drug coverage during annual enrollment is important if you take regular medications.
Medigap — Medicare Supplement Insurance
Medigap (Medicare Supplement Insurance) is optional private insurance that helps pay your share of costs in Original Medicare — things like deductibles, coinsurance, and copayments. Medigap policies are standardized in most states (plans are labeled with letters such as Plan G or Plan N).
To buy Medigap, you must have Part A and Part B. You pay a separate monthly premium to the Medigap insurer in addition to your Part B premium (and Part A premium, if you pay one). Medigap generally does not cover prescription drugs — most people pair it with a standalone Part D plan.
Medigap is designed for people in Original Medicare, not Medicare Advantage. You cannot use Medigap to pay costs within a Medicare Advantage plan.
How the parts fit together — at a glance
Original Medicare path: Part A + Part B, often plus a standalone Part D plan and/or a Medigap policy.
Medicare Advantage path: One Part C plan that includes Part A and Part B benefits and usually Part D drug coverage.
Neither path is automatically right for everyone. The best fit depends on your doctors, prescriptions, budget, and how you prefer to manage care — topics covered in other Learning Center articles.
Verify with official sources
Medicare rules and costs change. For the most current, authoritative information, review the official Medicare.gov overview of the parts of Medicare:
Parts of Medicare — Medicare.gov
You can also call 1-800-MEDICARE or contact your State Health Insurance Assistance Program (SHIP) for free, unbiased help.
Important reminder
This article is educational only. It does not list every plan available in your area and does not recommend specific carriers, products, or enrollment actions. We are not connected with or endorsed by the U.S. government or the federal Medicare program.
