Medicare Parts A, B, C, and D Explained in Plain English

Medicare is the federal health insurance program for people 65 and older, and for some younger people with disabilities. It is divided into parts — A, B, C, and D — and each part covers different things. Understanding the basics helps you avoid surprises and late-enrollment penalties.

Part A: Hospital Coverage

Part A covers inpatient hospital stays, skilled nursing facility care, hospice, and some home health care. Most people do not pay a monthly premium for Part A if they or their spouse worked and paid Medicare taxes for at least 10 years (40 quarters). However, Part A has deductibles and copays when you actually use it — for example, a deductible for each hospital stay.

Part B: Medical Coverage

Part B covers outpatient services — doctor visits, preventive care, lab tests, X-rays, mental health services, and some medical equipment like wheelchairs. Most people pay a monthly premium for Part B. In 2024, the standard premium was about $174.70 per month, but people with higher incomes pay more. Part B also has an annual deductible and then you pay 20% of most services after that.

Part C: Medicare Advantage

Part C is an alternative to original Medicare (Parts A and B). Instead of the government paying your claims directly, you enroll in a private insurance plan that bundles A and B together — and often adds dental, vision, and hearing coverage. You still pay the Part B premium plus whatever the plan charges. Plans vary widely by cost and network.

Part D: Prescription Drug Coverage

Part D covers prescription drugs. You buy a standalone Part D plan to add drug coverage to original Medicare, or choose a Medicare Advantage plan that includes it. Plans vary by which drugs they cover (called a formulary) and what you pay. There is a penalty if you go more than 63 days without creditable drug coverage after you first become eligible.

When to enroll

Your Initial Enrollment Period is 7 months: the 3 months before your 65th birthday, the month you turn 65, and the 3 months after. Missing this window without a valid reason (like active employer coverage) can result in permanent premium increases.

Quick Tip: Medicare.gov has a free Plan Finder tool that lets you compare all Medicare Advantage and Part D plans available in your zip code, including costs and covered drugs.