Medicare Parts A, B, C & D Explained: A Plain-Language Guide

When you first approach Medicare, the alphabet-based naming system can feel overwhelming. Part A, Part B, Part C, Part D — and then Medigap on top of that. This guide cuts through the confusion and explains exactly what each part covers, what it costs, and how they work together.

Medicare Part A: Hospital Insurance

Part A covers inpatient hospital stays, skilled nursing facility care, hospice care, and some home health services. Most people receive Part A premium-free because they (or their spouse) paid Medicare taxes for at least 10 years while working.

• Inpatient hospital care (after a $1,676 deductible per benefit period in 2026)
• Skilled nursing facility care (days 1–20 fully covered; days 21–100 with a $209.50/day coinsurance)
• Hospice care for terminal illness
• Limited home health services

Medicare Part B: Medical Insurance

Part B covers outpatient services — doctor visits, preventive care, lab tests, durable medical equipment, and most outpatient procedures. Unlike Part A, Part B requires a monthly premium. The standard premium in 2026 is $185.00/month, though higher-income beneficiaries pay more through IRMAA surcharges.

• Doctor visits and specialist consultations
• Preventive screenings (mammograms, colonoscopies, annual wellness visits)
• Outpatient surgery and procedures
• Durable medical equipment (wheelchairs, walkers, CPAP machines)
• Mental health services
• Ambulance services

Medicare Part C: Medicare Advantage

Part C is not a separate benefit — it is an alternative way to receive your Part A and Part B benefits through a private insurance company approved by Medicare. Medicare Advantage plans must cover everything Original Medicare covers, and most also include Part D prescription drug coverage and extras like dental, vision, and hearing.

The trade-off: Medicare Advantage plans typically have lower premiums but use provider networks (HMO or PPO), meaning you may need referrals or be limited to in-network providers. They are an excellent choice for people who want low monthly costs and don't mind staying within a network.

Medicare Part D: Prescription Drug Coverage

Part D covers prescription drugs and is offered through private insurance companies. If you have Original Medicare (Parts A and B), you need to enroll in a standalone Part D plan separately. If you have a Medicare Advantage plan, drug coverage is usually included.

Part D plans vary significantly in which drugs they cover (the formulary) and what you pay. Comparing plans annually during Open Enrollment (October 15 – December 7) is critical, as your medications and plan formularies change every year.

How the Parts Fit Together

You have two main paths when you become Medicare-eligible:

• Path 1 — Original Medicare + Medigap + Part D: You keep Parts A and B, add a Medigap supplement policy to cover the gaps (deductibles, coinsurance), and add a standalone Part D plan for drugs. This gives you the most flexibility — any doctor who accepts Medicare nationwide.
• Path 2 — Medicare Advantage (Part C): You replace Original Medicare with an all-in-one private plan that typically includes drug coverage and extra benefits. Lower premiums, but network restrictions apply.

When to Enroll

Your Initial Enrollment Period (IEP) is a 7-month window that begins 3 months before the month you turn 65, includes your birthday month, and extends 3 months after. Missing this window can result in permanent late enrollment penalties. If you have employer coverage, special rules may apply.