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What are the parts of Medicare (A, B, C and D)?

Four letters, two of them government coverage and two of them private. Here is what each one does and how they fit together.

Updated August 17, 2026 · 3 min read

Medicare got built in pieces over sixty years, and each piece got a letter. That is the only reason it looks complicated. Once you see which letters are government coverage and which are private products, it settles down.

Part A: hospital

Part A covers you when you are admitted as an inpatient. Hospital stays, skilled nursing care after a qualifying hospital stay, hospice, and some home health.

Most people pay no monthly premium for it, because they already paid through payroll taxes over about 10 years of work.

Part B: everything else medical

Doctor visits, specialists, lab work, X-rays and imaging, outpatient surgery, physical therapy, durable medical equipment like walkers and oxygen, and most preventive care.

Part B has a monthly premium almost everyone pays, usually deducted from your Social Security check.

A and B together are what people mean by Original Medicare. That is the federal government paying your providers directly.

Part C: Medicare Advantage

This is the one that confuses people, because it is not additional coverage. Part C is an alternative way to receive A and B.

You stay enrolled in Medicare, keep paying your Part B premium, and a private insurance company takes over administering your care. Most of these plans fold in drug coverage and add extras like dental, vision, hearing and a gym benefit.

In exchange you use a network of doctors and hospitals, you may need referrals, and you pay copays as you go rather than a large supplement premium. See the full comparison.

Part D: prescriptions

Drug coverage, sold by private companies under federal rules. You can buy it as a standalone plan alongside Original Medicare, or get it bundled inside most Medicare Advantage plans.

Every Part D plan has its own formulary, meaning its own list of covered drugs and its own tiers. Two plans with identical premiums can price your specific medication very differently.

The letter that is not a letter

Medigap, also called Medicare Supplement, is the piece with no letter of its own. It pairs only with Original Medicare and pays the share Medicare leaves behind. Confusingly, Medigap policies are themselves labeled with letters like Plan G and Plan N, which is a different alphabet entirely.

Plan G the Medigap policy has nothing to do with Part G. There is no Part G.

How they actually get combined

In practice there are only two sensible combinations.

• A plus B plus a Medigap policy plus a standalone Part D plan. Any doctor nationwide, predictable costs, higher monthly premium.
• A plus B plus a Medicare Advantage plan that includes drug coverage. Network based, lower or no extra premium, costs arrive as copays.

You cannot hold a Medigap policy and a Medicare Advantage plan at the same time. It is one path or the other, and switching later is not always allowed.