Medicare is the federal health insurance program for people 65 and older, certain younger people with disabilities, and people with End-Stage Renal Disease. Here's what you need to know about each part.

Part A — Hospital Insurance

Part A covers inpatient care:

Hospital stays (semi-private room, meals, nursing)
Skilled nursing facility care (up to 100 days after a qualifying hospital stay)
Hospice care
Some home health care

Most people pay $0 premium for Part A because they (or their spouse) paid Medicare taxes for at least 10 years. If you don't qualify for premium-free Part A, it costs up to $518/month (2025).

The Part A deductible is $1,676 per benefit period (2025). A benefit period starts when you're admitted and ends when you've been out of a hospital or skilled nursing facility for 60 consecutive days.

Part B — Medical Insurance

Part B covers outpatient care:

Doctor visits and specialist appointments
Preventive services (many are free — no copay, no deductible)
Outpatient surgery
Durable medical equipment (wheelchairs, walkers, oxygen)
Mental health services
Ambulance services

The standard Part B premium is $185/month (2025). If your income is higher, you may pay more through the Income-Related Monthly Adjustment Amount (IRMAA). After the $257 annual deductible, you typically pay 20% coinsurance for most services.

Part C — Medicare Advantage

Medicare Advantage plans are offered by private insurance companies as an alternative to Original Medicare. They must cover everything Parts A and B cover, and most include Part D drug coverage too.

Potential benefits:

$0 premiums available (you still pay Part B premium)
Out-of-pocket maximum (Original Medicare has none)
Often includes dental, vision, hearing, and fitness
May include transportation and over-the-counter allowances

Tradeoffs:

Usually requires staying in a provider network
May require referrals for specialists
May require prior authorization for some services

Part D — Prescription Drug Coverage

Part D covers prescription medications:

Available as standalone plans (with Original Medicare) or built into Medicare Advantage
Each plan has its own formulary (list of covered drugs)
$2,000 annual out-of-pocket cap starting in 2025 (Inflation Reduction Act)
$35/month insulin cap for all Part D plans
Extra Help/Low-Income Subsidy available for those with limited income

Key enrollment deadlines:

Initial Enrollment: 7-month window around your 65th birthday
Annual Enrollment: October 15 – December 7 (changes effective January 1)
Medicare Advantage Open Enrollment: January 1 – March 31
Missing deadlines can mean lifetime penalties — 10% added to Part B premium for each year you delay

What Medicare does NOT cover:

Long-term care (nursing home custodial care)
Most dental, vision, and hearing (unless you have Medicare Advantage)
Care outside the US (with limited exceptions)
Cosmetic surgery