Medicare Parts A, B, C, and D: What Each One Covers

How Medicare is structured

Medicare is the federal health insurance program primarily for people 65 and older, as well as certain younger individuals with qualifying disabilities. It is not a single plan. It has four distinct parts, each covering a different category of care. Knowing what each part does helps you figure out what you already have, what you might be missing, and where to focus when comparing options.

For a broader look at coverage choices after 65, see the starter guide to health coverage for seniors.

Part A: hospital insurance

Part A covers inpatient hospital stays, care in a skilled nursing facility following a qualifying hospital stay, some home health services, and hospice care. Most people do not pay a monthly premium for Part A if they or their spouse worked and paid Medicare taxes for at least 10 years.

Part A does not cover everything that happens inside a hospital. Physician fees during a hospital stay are billed separately under Part B. There are also deductibles and coinsurance costs that apply per benefit period, not per year, which can add up if you have multiple hospitalizations.

Part B: medical insurance

Part B covers outpatient services: doctor visits, preventive screenings, lab tests, durable medical equipment, and some home health services. It also covers medically necessary services like physical therapy and mental health care received outside a hospital.

Unlike Part A, Part B charges a standard monthly premium, and most enrollees also pay 20% of the Medicare-approved cost for covered services after meeting the annual deductible. That 20% has no cap under Original Medicare, which is one reason many people look at supplemental coverage. The guide to Medigap policies explains how those gaps can be addressed.

Preventive care under Part B, such as the annual wellness visit and certain screenings, is typically covered at no cost. The overview of preventive care coverage lists what qualifies.

Part C: Medicare Advantage

Part C is not a separate category of benefits. It is an alternative way to receive your Medicare coverage through a private insurer approved by the federal government. Medicare Advantage plans are required to cover everything Original Medicare covers, and many include prescription drug coverage, plus extras such as dental, vision, and hearing.

Trade-offs exist. Most Medicare Advantage plans use provider networks, so your choice of doctors and hospitals may be more limited than with Original Medicare. Costs vary by plan and by location. Premiums, copays, and out-of-pocket maximums differ across plans in the same area.

Part D: prescription drug coverage

Part D is standalone prescription drug coverage available to anyone enrolled in Medicare. It is offered through private insurers and comes as either a standalone plan added to Original Medicare or built into a Medicare Advantage plan.

Each Part D plan has a formulary, which is a list of covered drugs organized into tiers that carry different cost-sharing amounts. If a medication you take is not on a plan's formulary, or sits on a high-cost tier, your out-of-pocket costs can be significant. Comparing formularies before enrolling is one of the more practical steps a person can take.

Going without Part D when you first become eligible, and not having other creditable drug coverage, can result in a late enrollment penalty added permanently to your premium.

This article is for general informational purposes only and is not personalized insurance, financial, or medical advice. Coverage terms, costs, and eligibility rules vary. Review official Medicare materials at Medicare.gov and consult a licensed insurance counselor or benefits adviser for guidance specific to your situation.