Medicare Parts A, B, C, and D

Medicare comes in four letters: A covers hospitals, B covers doctors, D covers drugs, and C bundles them into a private plan. Knowing which is which is the first step to not overpaying for any of them.

Why does Medicare come in four letters, and which ones do you actually need? Each part covers a different slice of your health care, and you pick which to use. A is the hospital, B is the doctor, D is the pharmacy, and C is a private bundle of all three.

Part A: hospital

This covers inpatient hospital stays, skilled nursing after a hospital stay, and some home health and hospice. Most people pay no premium for Part A because they paid in through payroll taxes during their working years. It’s the one piece of Medicare that’s usually already paid for.

Part B: doctors

This covers doctor visits, outpatient care, lab work, and preventive services. Part B has a monthly premium, $202.90 for 2026 at the standard rate, plus an annual deductible of $283. Higher earners pay more through IRMAA, the income-based surcharge. Together, A and B are what people mean by “Original Medicare.” When to sign up and how late enrollment is penalized is covered in Medicare Part B enrollment decisions.

Part D: drugs

This covers prescription drugs and runs through a private plan you choose. Premiums vary by plan, and high earners pay a separate Part D IRMAA surcharge on top of whatever the plan charges. Skip it when you’re first eligible without other creditable coverage and you face a lifelong late penalty.

Part C: the bundle

Part C, also called Medicare Advantage, is a private plan that rolls A, B, and usually D into one package, often with dental or vision attached. The catch is networks. Advantage plans steer you to their doctors and hospitals, while Original Medicare plus a supplement lets you see almost anyone.

The part most people miss

The real fork is Original Medicare plus a Medigap supplement versus Medicare Advantage, and it’s hard to undo. You usually get one clean shot at a supplement with no medical underwriting, right when you first enroll. Wait, try Advantage, then decide you want to switch back, and an insurer can decline you or charge more based on your health. For affluent households who want broad access to specialists, that one-time window is the decision that matters most.

Four letters, two real choices. Get Part B’s timing right and get the Medigap-versus-Advantage fork right, and the rest follows.