Medicare Parts A, B, C, D — Explained Without the Alphabet Soup

Medicare has four parts, and somewhere along the way somebody decided to name them after the first four letters of the alphabet. Helpful? Not really. So let's translate.

Here is the entire alphabet soup in one sentence: A is hospital, B is doctor, C is the bundled alternative, and D is drugs. Everything else is a footnote.

Part A — the hospital part

Part A covers inpatient hospital stays, skilled nursing for a limited window after a hospital stay, hospice, and some home health. Most people pay $0 premium for Part A because they (or a spouse) paid into it for 40 quarters through payroll taxes.

The catch: there's a hospital deductible per benefit period (around $1,676 in 2025) and daily coinsurance if your stay runs long. Part A is not "free" — it's "free until something happens."

Part B — the doctor part

Part B covers doctor visits, outpatient care, preventive services, lab work, durable medical equipment, and most of what happens outside a hospital bed. The standard premium in 2025 is $185/month, with higher amounts for higher incomes (that's IRMAA — see below).

After a small annual deductible, Part B pays 80%. You pay the other 20% — with no cap. That uncapped 20% is the reason Parts C and the Medigap world exist.

Part C — Medicare Advantage

Part C is not a separate benefit. It's a private alternative that bundles A + B (and usually D) into one plan from a private insurer. These plans often add dental, vision, hearing, gym memberships, and a hard out-of-pocket maximum — but they typically use networks and require referrals or prior authorization.

Premiums can be as low as $0/month, but "$0 premium" doesn't mean "$0 cost." Copays, networks, and the out-of-pocket max do the real work.

Part D — the drug part

Part D covers prescription drugs through a standalone plan (paired with Original Medicare) or built into a Medicare Advantage plan. Plans vary wildly by formulary — the same pill can be tier 1 on one plan and tier 4 on another. This is why "what's the cheapest Part D plan?" is the wrong question. The right one is "what's the cheapest plan for my drugs."

Big change for 2025: out-of-pocket drug costs are capped at $2,000/year. The donut hole is officially dead.

What about Medigap?

Medigap (Medicare Supplement) isn't a "part." It's a private policy you add to Original Medicare (A + B) to pay the 20% Part B leaves behind, plus deductibles and coinsurance. You can't have Medigap and Medicare Advantage at the same time — it's one road or the other.

The takeaway

A and B are the foundation. C is a bundled alternative. D handles drugs. Medigap fills the holes in A and B if you stay with Original Medicare. That's it — you now know more than most people who turn 65.

Which road fits depends on your doctors, your meds, your travel habits, and your tolerance for surprises. That's a 20-minute conversation, not a guessing game.

Educational only — not tax, legal, or medical advice. Premiums and deductibles are set annually by CMS; verify current figures before making decisions.