Parts of Medicare: A, B, C, and D, what each one covers

One of the most common sources of confusion: Medicare isn't a single plan. It's four separate parts (A, B, C, and D) that combine into a handful of common configurations.

On this page we explain each part and how they stack up. If you're just starting, we recommend the overview at What is Medicare? first.

What it covers. Inpatient hospital stays, skilled nursing facility care after a hospital admission, hospice, and some home-health services.

What it costs. Free for most beneficiaries, as long as they (or a spouse) worked at least 40 quarters paying Medicare taxes (about 10 years). With fewer quarters, Part A is still available but comes with a monthly premium set yearly by CMS.

On top of the premium, hospital care has a deductible and coinsurance for longer stays, those amounts also reset yearly per CMS.

What Part A doesn't cover:

• Long-term care (e.g., permanent nursing-home stays unrelated to rehab).
• Most doctor visits (those are Part B).
• Outpatient prescription drugs (those are Part D).

What it covers. Outpatient care, basically everything outside the hospital. Doctor visits, specialists, lab work, preventive services (vaccines, screenings, annual wellness visit), ambulance services, some vaccines, durable medical equipment (wheelchairs, oxygen), and outpatient rehab.

What it costs. A monthly premium set yearly by CMS, usually deducted directly from Social Security benefits. Higher-income beneficiaries pay a surcharge called IRMAA (Income-Related Monthly Adjustment Amount).

Part B also has an annual deductible. After that, Medicare pays 80% of approved costs and your parent pays the remaining 20%, unless they have additional coverage that fills the gap.

Parts A and B together are what's called Original Medicare.

What it is. An alternative to Original Medicare. Instead of getting coverage directly from CMS, your parent enrolls in a private Medicare-approved plan that bundles Parts A and B (and usually Part D, called MAPD) into one product.

How it works. They stay enrolled in Medicare, but coverage is administered by a private insurance company under contract with CMS. Plans typically have a network of doctors and hospitals that must be used for full coverage.

To enroll in Medicare Advantage, your parent must already have active Part A and Part B.

For a deeper breakdown (networks, HMO vs. PPO, what to ask before signing up), see the Medicare Advantage page.

What it is. A standalone prescription drug plan (PDP). Unlike Parts A and B, Part D plans are run by private insurers under CMS rules, not directly by CMS.

How it works. Part D can be bought as a separate plan to pair with Original Medicare, or built into a Medicare Advantage plan (MAPD). Every Part D plan has its own formulary, the list of drugs it covers. The same prescription can cost very different amounts from one plan to the next, because each plan places drugs in different tiers.

Beyond the four main parts, there's a category of supplemental policies called Medigap (Medicare Supplement). Medigap doesn't replace any Medicare part. It pairs with Original Medicare (A + B) and helps cover the out-of-pocket costs Medicare itself leaves behind.

How Medigap works and why the six-month enrollment window after Part B starts is so critical, covered on the Medicare Supplement page.

Once your parent ages into Medicare, they have a few main paths:

• Path 1: Original Medicare alone. Just A + B. Hospital and medical coverage, no drugs, and still 20% coinsurance after the deductible, with no annual cap on what you pay out of pocket. Rarely optimal without something else added on.
• Path 2: Original Medicare + Part D. A + B plus a standalone drug plan. Still no help with the 20%, but at least drugs are covered.
• Path 3: Original Medicare + Medigap + Part D. The classic setup for people who want freedom to choose doctors and predictable costs. Medigap covers what Original Medicare doesn't, and Part D handles drugs.
• Path 4: Medicare Advantage (usually MAPD with built-in Part D). One plan, one card, one network. Often lower premiums in exchange for being limited to the plan's network.
• Path 5: Medicare Advantage plus a hospital indemnity plan (HIP). A Medicare Advantage (or MAPD) plan as the base, with a private hospital indemnity plan (HIP) helping cover that plan's largest out-of-pocket costs (co-pay, deductible, coinsurance) for an affordable monthly premium.

Which path is right? It depends on your parent's doctors, medications, travel patterns, budget, and how much care they use. That's why we talk through their actual situation before recommending anything.

We're a licensed, independent insurance agency serving Polish-speaking families across 17 states. We walk through which combination of Parts makes sense for your parent, comparing carriers, verifying their doctors and medications, and explaining the trade-offs in plain English to you and in Polish to them.

Jakub Słomczewski Licensed Insurance Agent A, B, C, and D. We'll put the pieces together with your family, calmly.

Working with our agency costs your family nothing. Agents are paid directly by the insurance carriers.