Blog / Medicare

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

Medicare has four parts. A and B come from the government, C and D come from private companies. Here is what each one pays for and how they fit together.

Updated September 3, 2026 · 4 min read · by Gerino Alejos

Medicare has four parts. Part A pays for hospital stays. Part B pays for doctor visits and care outside the hospital. Part C, called Medicare Advantage, is a private plan that delivers Part A and Part B for you. Part D pays for prescription drugs.

Medicare was built in pieces over sixty years, and each piece got a letter. That is the only reason it looks complicated. For the overview, see what Medicare is and how it works.

Part A: hospital coverage

Part A pays when you are admitted to the hospital as an inpatient. It also pays for skilled nursing care (nursing and therapy in a facility while you recover) after a qualifying hospital stay, hospice (comfort care near the end of life), and some home health care.

Most people pay no monthly premium (the monthly bill for the coverage) for Part A. You already paid through the Medicare tax on your paychecks over about 10 years of work.

Part B: doctors and outpatient care

Part B pays for doctor visits, specialists, lab work, X-rays and scans, outpatient surgery (where you go home the same day), physical therapy, and most preventive care such as screenings. It also pays for durable medical equipment, gear like walkers and oxygen that you use at home.

Part B has a monthly premium that almost everyone pays. It usually comes out of your Social Security check.

Part A and Part B together are called Original Medicare. With Original Medicare, the federal government pays your doctors and hospitals directly.

Part C: Medicare Advantage

Part C confuses people because it is not extra coverage. A private insurance company delivers your Part A and Part B benefits instead of the government.

You stay in Medicare and keep paying your Part B premium. Most Advantage plans include drug coverage and add extras like dental, vision, hearing and a gym benefit.

In return you use the plan's network, the list of doctors and hospitals it has contracts with, and you may need a referral (your primary doctor's approval) to see a specialist. You pay copays, a set amount per visit, as you go instead of a larger monthly premium for a supplement. See the full comparison and what Medicare Advantage is.

Part D: prescription drugs

Part D pays for the prescriptions you fill at a pharmacy. Private companies sell it under federal rules. You can buy it as a standalone plan, a separate drug plan that sits next to Original Medicare, or get it built into most Advantage plans.

Every Part D plan has its own formulary, the list of drugs it covers, and its own tiers, the price levels it sorts those drugs into. Two plans with the same premium can charge very different amounts for your medication. See how Part D works.

Medigap plan letters are not parts of Medicare

Medigap, also called a Medicare Supplement, is the piece with no letter of its own. It only works with Original Medicare, and it pays the share of the bill that Medicare leaves to you. See what Medigap is.

Medigap policies are sold under their own letters, like Plan G and Plan N, which is a separate alphabet. Plan G is a Medigap policy. There is no Part G.

How the parts combine into two paths

In practice there are two sensible ways to put the parts together.

• Part A and Part B, plus a Medigap policy, plus a standalone Part D plan. Any doctor nationwide, predictable costs, and a higher monthly premium.
• Part A and Part B, plus a Medicare Advantage plan that includes drug coverage. You use the plan's network, the extra premium is low or zero, and your costs show up as copays.

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

Where to enroll in each part

Each part is joined in a different place. Doing all of them in one sitting avoids the gaps that lead to penalties, the extra charges added to your premium for signing up late.

• Part A and Part B through Social Security. See how to apply online.
• A Medicare Advantage plan through the plan itself. See how to enroll in an Advantage plan.
• A standalone drug plan next to Original Medicare. See how to sign up for Part D.
• A Medicare Supplement policy through the insurance company. See how to enroll in a supplement.

If you are not sure which path fits you, we can walk through both with you. Call our McAllen office at (956) 687 3334, or enter your ZIP code in the plan pricing box on this page.

Gerino Alejos

Licensed insurance agent · License 3128710 · NPN 18243381

Owner of McAllen Insurance Group, an independent agency on North 10th Street in McAllen. Works with clients across Hidalgo, Cameron and Starr counties on Medicare, Marketplace health, life and auto coverage. Se habla español.