What are Medicare Parts A, B, C, and D?

Part A is hospital insurance covering inpatient stays, skilled nursing, and hospice (usually premium-free). Part B is medical insurance covering doctor visits, outpatient care, and preventive services (monthly premium). Part C is Medicare Advantage, a private all-in-one plan. Part D is prescription drug coverage. Parts A and B together are called Original Medicare.

Is Medicare Part A free?

Most people get premium-free Part A if they or their spouse paid Medicare taxes for about 10 years (40 quarters). You may still owe a deductible per benefit period for hospital stays. Part B, by contrast, always has a monthly premium.

Do I need Part C and Part D?

Not both. Part C (Medicare Advantage) usually already includes Part D drug coverage, so you don't add a separate Part D plan. If you choose Original Medicare with a Medigap supplement instead, you'd add a standalone Part D plan for drug coverage. It's an either/or path.

What is the difference between Part C and Original Medicare?

Original Medicare is Parts A and B, run by the federal government, letting you see any provider that accepts Medicare. Part C (Medicare Advantage) is a private plan that bundles A, B, and usually D, typically with a network of providers and often extra benefits like dental and vision. You choose one path or the other.

Which Medicare parts do I actually enroll in?

Most people enroll in Part A and Part B first (Original Medicare). Then you choose: add a Medigap supplement plus a Part D drug plan, or enroll in a Medicare Advantage (Part C) plan that combines everything. A licensed California agent can walk you through which path fits your doctors, drugs, and budget at no cost.

California Medicare Guide

How Medicare Works New to Medicare / Turning 65Parts A, B, C, DAdvantage Plans Medigap Plans Advantage vs Medigap Enrollment Periods Birthday Rule (CA)Costs & Giveback

Medicare Parts A, B, C, and D Explained (2026)

Key Takeaways

Part A = hospital insurance (inpatient, skilled nursing, hospice). Usually premium-free.
Part B = medical insurance (doctors, outpatient, preventive care). Has a monthly premium.
Part C = Medicare Advantage — a private plan that bundles A, B, and usually D.
Part D = prescription drug coverage, through private plans.
Parts A + B together are called Original Medicare. From there you add Medigap + Part D, OR choose Part C.

Medicare Part A, B, C, and D Explained SIMPLY - Watch on YouTube

Medicare's four parts each do a different job. Once you understand what A, B, C, and D cover, the rest of Medicare makes sense. Here's each one, in plain English.

What Is Medicare Part A?

Part A — Hospital Insurance

Covers inpatient hospital stays, skilled nursing facility care, hospice, and some home health care. Most people qualify for premium-free Part A if they or a spouse paid Medicare taxes for about 10 years. There's a deductible per benefit period.

What Is Medicare Part B?

Part B — Medical Insurance

Covers doctor visits, outpatient care, preventive services (like screenings and vaccines), lab tests, and durable medical equipment. Part B has a monthly premium (higher earners pay more via IRMAA) and an annual deductible, after which you typically pay 20% of costs.

Together, Part A and Part B make up "Original Medicare." See our Medicare costs page for premium details.

What Is Medicare Part C (Medicare Advantage)?

Part C — Medicare Advantage

A private, all-in-one alternative to Original Medicare. A Medicare Advantage plan bundles Part A, Part B, and usually Part D, often adding extras like dental, vision, and hearing. Plans use provider networks and often have low or $0 premiums.

What Is Medicare Part D?

Part D — Prescription Drugs

Covers prescription medications through private plans. You can get Part D as a standalone plan (paired with Original Medicare + Medigap) or built into a Medicare Advantage plan. Each plan has its own formulary (list of covered drugs), so matching your prescriptions matters.

How the Parts Fit Together

Your path	Parts you use
Original Medicare + Medigap	Part A + Part B + a Medigap supplement + a standalone Part D drug plan
Medicare Advantage	Part C (which includes A + B + usually D in one plan)

The key thing to understand

Parts A and B (Original Medicare) are your foundation — then you choose how to fill the gaps. Original Medicare alone leaves you exposed to that 20% coinsurance with no cap. So you either add a Medigap supplement + Part D, OR replace the whole thing with a Medicare Advantage plan. That's the real decision. We help you compare both approaches for free — see Advantage vs Medigap.