Medicare 101

Medicare Parts
Explained: A, B, C, and D

Medicare is made up of four main Medicare Parts, each covering a different slice of your healthcare. Here is what each part does.

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Part A: Hospital insurance

Part A covers inpatient care. Most people pay $0 in premiums for Part A if they or their spouse worked and paid Medicare taxes for at least 10 years (40 quarters). If you paid fewer than 40 quarters, you pay a monthly premium.

Inpatient hospital stays: Semi-private room, meals, general nursing, and hospital services.
Skilled nursing facility care: Up to 100 days per benefit period following a qualifying 3-day hospital stay.
Hospice care: Pain management and support for terminal illness, typically in your home.
Some home health care: Part-time skilled nursing or therapy ordered by your doctor.

Part B: Medical insurance

Part B covers outpatient care. The standard premium is set by CMS each year (higher earners may pay an IRMAA surcharge). After the yearly Part B deductible, Original Medicare generally covers 80% of approved costs. You pay the remaining 20%.

Doctor visits: Primary care and specialist visits, including telehealth.
Preventive services: Annual wellness visits, flu shots, mammograms, and colonoscopies.
Outpatient procedures: Surgeries, lab tests, and imaging done without an overnight stay.
Durable medical equipment: Wheelchairs, walkers, CPAP machines, and blood sugar monitors.

Part C: Medicare Advantage

Medicare Advantage is an all-in-one alternative to Original Medicare offered by private insurers approved by CMS. These plans must cover everything Parts A and B cover, and most include Part D drug coverage. Many also add dental, vision, and hearing benefits not covered by Original Medicare.

Read the Medicare Advantage guide →

Part D: Prescription drug coverage

Part D covers prescription medications. These plans are sold by private insurers and vary widely in which drugs they cover (the formulary), what tiers those drugs fall into, and what you pay. If you have Original Medicare without a drug plan or other creditable coverage, waiting past your first chance to enroll can mean a late-enrollment penalty.

How to avoid penalties →

Medigap: Supplemental coverage

Medigap (also called Medicare Supplement) is private insurance that fills the cost-sharing gaps left by Original Medicare, including the Part B 20% coinsurance and hospital deductibles. Medigap works alongside Original Medicare, not instead of it. You cannot have both a Medigap plan and a Medicare Advantage plan at the same time.

Read the Medigap guide →

Common questions

Do I need to enroll in all the parts?

Most people take Part A and Part B. Then they add either a Medigap plan plus Part D, or a Medicare Advantage plan that usually includes drugs.

What is the difference between Original Medicare and Medicare Advantage?

Original Medicare is A and B, usually paired with Medigap and Part D. Advantage is a private plan that becomes how you get A and B, often with D and extras. Compare the two paths.

Can I have Part A without Part B?

Sometimes, especially if you or a spouse still has employer coverage. Skipping Part B without creditable coverage can trigger a late-enrollment penalty later.

Is there a penalty for not signing up for Part D?

Yes, if you go without creditable drug coverage past your first chance to enroll. Read the penalty page.