Medicare basics — when and how to enroll

Medicare is the federal health insurance program for people 65+, certain younger people with disabilities, and people with End-Stage Renal Disease. Here’s how it works.

The four parts

Part A — Hospital Insurance

Covers inpatient hospital stays, skilled nursing facility care, hospice, some home health care. Most people don’t pay a premium for Part A if they paid Medicare taxes for 10+ years.

Part B — Medical Insurance

Covers doctor visits, outpatient care, preventive services, durable medical equipment. Standard 2026 premium: ~$185/month, higher for high-income enrollees (IRMAA surcharges).

Part C — Medicare Advantage

A private alternative to Original Medicare (A+B). Offered by private insurers, regulated by Medicare. Often includes Part D, dental, vision, and other benefits. Premiums vary widely (some are $0/month, some $100+).

Part D — Prescription Drug Coverage

Outpatient prescription coverage. Either standalone (added to Original Medicare) or included in Medicare Advantage. Premiums vary.

Original Medicare vs. Medicare Advantage

This is the most important decision in Medicare enrollment.

Original Medicare (Part A + B + optional D + optional Medigap):

• See any doctor that accepts Medicare (huge nationwide network)
• No referrals
• More predictable costs (Medigap covers most copays)
• Higher monthly premium total (B + Medigap + D)
• Not capped — no max out-of-pocket
• Limited extras (no dental, vision, hearing without separate coverage)

Medicare Advantage (Part C):

• Network-restricted (typically HMO or PPO)
• Often includes Part D, dental, vision, fitness benefits
• Lower or zero premium beyond Part B
• Has annual max out-of-pocket
• Requires staying in network
• Less flexibility traveling

There’s no objectively correct choice. Roughly: people who travel, see lots of specialists, or want network flexibility lean Original + Medigap. People who want all-in-one simplicity and lower premiums lean Medicare Advantage.

Initial enrollment period

The 7-month window around your 65th birthday:

• 3 months before your 65th birthday month
• Your birthday month
• 3 months after

Sign up early in the window (before birthday) to ensure coverage starts the first of your birthday month.

Late enrollment penalties

Miss the initial enrollment period without other qualifying coverage and:

• Part B penalty: 10% added to your monthly premium for each 12-month period you delayed — for the rest of your life
• Part D penalty: 1% per month of delay — for the rest of your life

The penalties are permanent. If you’re approaching 65 and uncertain, talk to a Medicare counselor (free through state SHIP programs) before the enrollment window.

Working past 65

If you’re still working at 65 and have employer health coverage:

• Large employer (20+ employees): you can usually delay Medicare Part B without penalty
• Small employer (<20 employees): Medicare becomes primary at 65; delay risks penalty

When you leave employer coverage, you get an 8-month special enrollment period to sign up for Medicare without penalty.

Annual changes

Even after initial enrollment, you can change Medicare Advantage and Part D plans during:

• Annual Enrollment Period: October 15 - December 7 each year
• Medicare Advantage Open Enrollment: January 1 - March 31

Use these windows to reshop your plan. Premiums, formularies, and provider networks change every year.