Medicare Parts A, B, C, and D Explained

Medicare is organized into parts labeled with letters, and that alphabet soup trips up a lot of people. The good news: once you see what each part does, it is straightforward. Here is the plain-English version.

The Four Parts at a Glance

• Part A — hospital insurance
• Part B — medical insurance (doctors, outpatient care)
• Part C — Medicare Advantage, a private all-in-one alternative
• Part D — prescription drug coverage

Parts A and B together are known as Original Medicare.

Part A: Hospital Insurance

Part A covers inpatient hospital stays, skilled nursing facility care, hospice, and some home health care. Most people get Part A premium-free because they or a spouse paid Medicare taxes while working, though it still has deductibles and coinsurance.

Part B: Medical Insurance

Part B covers doctor visits, outpatient care, preventive services, lab tests, and durable medical equipment. Part B has a monthly premium and cost-sharing. Together, Parts A and B form the foundation of your Medicare coverage.

Part C: Medicare Advantage

Part C, or Medicare Advantage, is a private plan that bundles Parts A and B, usually adds Part D drug coverage, and often includes extras like dental, vision, and hearing. These plans use networks and cap your yearly out-of-pocket spending. You get your Medicare through the plan instead of directly from the government.

Part D: Prescription Drug Coverage

Part D covers prescription drugs. You can get it as a standalone plan added to Original Medicare, or built into a Medicare Advantage plan. Each plan has a formulary (its list of covered drugs), so the right Part D plan depends on the specific medications you take.

Where Medigap Fits

You may also hear about Medigap (Medicare Supplement). Medigap is not one of the lettered parts; it is private insurance that works alongside Original Medicare to pay the deductibles and coinsurance Medicare leaves behind. You choose either Medicare Advantage (Part C) or Original Medicare with a Part D plan and optional Medigap, not both. Our Medicare Advantage vs Medigap guide compares those two paths.