Skip to main content

    Medicare Parts A, B, C, and D Explained

    What Medicare Parts A, B, C, and D each cover, what they cost, and when you need to enroll — written clearly for first-time enrollees.

    4 min read · 5 steps · Checked April 2026

    1. Step 1. Understand which parts you need

      If you want original Medicare, you need Part A (hospital) and Part B (medical). Add a standalone Part D plan for prescription drugs, and optionally a Medigap supplement policy to cover gaps. Alternatively, choose a Part C Medicare Advantage plan that bundles everything together.

      Quick Tip

      Original Medicare gives you broader provider choice. Medicare Advantage often costs less but requires you to use a specific network of doctors and hospitals.

    2. Step 2. Check your enrollment window

      Mark your 65th birthday on the calendar. Your Initial Enrollment Period starts 3 months before that birthday month and ends 3 months after. If you are still on employer coverage through your own job, you may delay Medicare without penalty — call 1-800-MEDICARE to confirm your specific situation.

      Warning

      If you are on COBRA or retiree health coverage (not active employer coverage), those do not count as creditable coverage for Medicare purposes. Enroll in Medicare on time to avoid penalties.

    3. Step 3. Sign up for Part A and Part B

      You can enroll online at ssa.gov/medicare, by phone at 1-800-772-1213, or in person at a Social Security office. If you already receive Social Security retirement benefits, you are usually enrolled in Part A and B automatically at 65.

    4. Step 4. Choose a Part D drug plan or Medicare Advantage plan

      Go to medicare.gov/plan-compare. Enter your zip code and list the medications you take. The tool will show you plans available in your area, what they cost, and whether your drugs are covered. Compare at least three plans before choosing.

      Quick Tip

      Plans change every year. Review your coverage each fall during Open Enrollment (October 15 – December 7) to make sure your plan still works for you.

    5. Step 5. Get help if you need it

      Every state has a free Medicare counseling program called SHIP (State Health Insurance Help Program). Trained counselors help you compare plans at no cost. Find your local SHIP at shiphelp.org or call 1-800-MEDICARE.

    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.

    Official sources

    Still stuck?

    A real person can walk you through it over the phone.

    Get help from a person

    Related guides