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Medicare Parts A, B, C, and D Explained

A plain-language guide to the four parts of Medicare — what each one covers and how they fit together. Based on Medicare.gov.

NCI source

Last reviewed: 2026-07-07

The short answer

Medicare has four parts. Part A covers hospital care, Part B covers doctor and outpatient care, Part C (Medicare Advantage) is a private plan that bundles A and B, and Part D covers prescription drugs. Together they cover most, but not all, health costs.

  • Part A is hospital insurance — inpatient stays and some skilled nursing and hospice care.

  • Part B is medical insurance — doctor visits, outpatient care, tests, and preventive services.

  • Part C (Medicare Advantage) is a private plan that bundles Parts A and B, often with drug coverage.

  • Part D covers prescription drugs and is offered through private plans.

Choose how you want to understand this

The full explanation.

The simple version

Medicare has four parts, each covering something different. Understanding them helps you know what your care will cost and where any gaps are. This is general information; your specific plan sets your exact benefits and costs.

The four parts

Here is what each part covers:

  • Part A — hospital insurance: inpatient stays, some skilled nursing, hospice, and some home health care
  • Part B — medical insurance: doctor visits, outpatient care, tests, equipment, and preventive services
  • Part C — Medicare Advantage: a private plan that bundles A and B, often with drug coverage and extras
  • Part D — prescription drug coverage through private plans

Two ways to get Medicare

You can use Original Medicare (Parts A and B), often adding a stand-alone Part D drug plan and a Medigap supplement. Or you can choose a Medicare Advantage (Part C) plan that bundles coverage, usually with a provider network. Each path has trade-offs in cost and choice of doctors.

Original Medicare plus Medigap and Medicare Advantage are two different paths — check which covers your cancer team.

Watch the gaps

Original Medicare usually leaves deductibles and about a 20% share of many costs, with no built-in yearly cap on Part A and B costs. That is why many people add a Medigap plan or choose Medicare Advantage. For cancer care, confirm your treatment, drugs, and doctors are covered.

Words to know

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Common questions

What is Part A?

Part A is hospital insurance. It covers inpatient hospital stays, some skilled nursing facility care, hospice, and some home health care. Most people get Part A without a monthly premium.

What is Part B?

Part B is medical insurance. It covers doctor visits, outpatient care, many tests, durable medical equipment, and preventive services. It has a monthly premium and, after a deductible, usually pays 80% of covered costs.

What is Part C?

Part C, also called Medicare Advantage, is a plan from a private company approved by Medicare. It bundles Part A and Part B and often includes drug coverage and extra benefits, but usually uses a network of providers.

What is Part D?

Part D covers prescription drugs. It is offered through private plans, either as a stand-alone plan added to Original Medicare or built into a Medicare Advantage plan.

Do A and B cover everything?

No. Original Medicare (Parts A and B) usually leaves you paying deductibles and about 20% of many costs, which is why some people add a Medigap supplement or choose a Medicare Advantage plan.

Questions to ask your doctor

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Quick quiz

Test your knowledge

0 of 4 answered

  1. Q1.What does Part A mainly cover?
  2. Q2.What is Part C also called?
  3. Q3.Which part covers prescription drugs?
  4. Q4.What gap does Original Medicare often leave?

This quiz checks understanding of educational content only. It is not medical advice. Open this quiz on its own page.

Related learning map

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Medicare Parts A, B, C, and D Explained