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

Medicare is the federal health insurance program for people 65 and older, some younger people with disabilities, and people with end-stage renal disease. The program is split into labeled parts. Each part decides a different kind of claim — who pays, and for what.

What each part pays

Part A is hospital insurance. It pays inpatient hospital stays, some skilled nursing after a qualifying hospital stay, hospice, and limited home health. A routine office visit is not a Part A claim.

Part B is medical insurance. It pays doctor services, outpatient care, durable medical equipment, and many preventive visits. Lab work and imaging ordered in an outpatient setting are usually Part B, not Part A.

Part D is the outpatient prescription drug benefit. Drugs given during a hospital stay can be billed under Part A or Part B. A retail or mail-order prescription is usually Part D.

Where Part C fits

Part C is Medicare Advantage. It is not a fourth hospital benefit and not a fifth letter sitting beside A, B, and D. It is a private plan that must cover at least what Original Medicare covers under Parts A and B. The plan then applies its own network, referral rules, and prior authorization. Most Advantage plans also include drug coverage.

Original Medicare is Part A plus Part B. Many people add a stand-alone Part D plan and, separately, a Medicare Supplement (Medigap) policy that helps with cost sharing. An Advantage plan is a different arrangement. A Supplement is not designed to sit on top of an Advantage plan.

The usual mix-up

A red, white, and blue Medicare card names Parts A and B. An Advantage card names the private plan. A drug card names the Part D contract. None of those cards, by themselves, answers whether a clinic is in network, whether a specialist needs a referral, or whether a drug is on the plan’s list.

People treat the word “Medicare” on a card as if it settled the whole program. It does not. The letter on the card is one fact. The plan type is a second fact. The network and the drug list are separate facts.

What to read on the document

On the card, read the plan name and whether it is Original Medicare, an Advantage plan, or a Part D plan. In the plan’s Evidence of Coverage or Annual Notice of Change, read which part pays which services and whether referrals or prior authorization apply. For a prescription, read the plan’s drug list for the year that matches the card.

Enrollment notices and explanations of benefits are easier to read once the part on the card is not treated as the entire program.

Educational only · Not medical, insurance, or legal advice