Medicare BasicsParts A, B, C & D

Part A — Hospital Insurance

Part A generally helps cover inpatient hospital care, skilled nursing facility care under qualifying conditions, hospice care and certain home health services. Many people qualify for premium-free Part A based on Medicare taxes paid while working.

Part B — Medical Insurance

Part B generally helps cover physician services, outpatient care, durable medical equipment, preventive services and other medically necessary services. Most people pay a monthly Part B premium, and higher-income beneficiaries may pay more.

IRMAA — Income-Related Monthly Adjustment Amount

IRMAA is an additional amount that some higher-income Medicare beneficiaries pay in addition to their regular Medicare premiums. It can apply to both Part B and Part D. Social Security generally determines IRMAA using modified adjusted gross income (MAGI) from your federal tax return from two years earlier, using income information provided by the IRS. The income thresholds and adjustment amounts are updated each year.

• Part B IRMAA: The adjustment is added to your monthly Part B premium.
• Part D IRMAA: The adjustment is paid in addition to your Medicare drug plan premium. It can apply whether your drug coverage is through a stand-alone Part D plan or included in a Medicare Advantage plan.

CMS publishes the official annual income brackets and adjustment amounts. See the current CMS IRMAA rate table for the published Part B and Part D income-related amounts.

If your income has gone down because of a qualifying life-changing event, you may be able to ask Social Security to use more recent income information. See Social Security Form SSA-44 for information about requesting a new IRMAA determination.

Part C — Medicare Advantage

Medicare Advantage, also called Part C, is an alternative way to receive your Medicare benefits through a private insurance company approved by Medicare. Medicare Advantage plans provide your Part A and Part B benefits and usually include Part D prescription drug coverage. Depending on the plan, provider networks, referrals, copayments, coinsurance and other plan rules may apply. Many plans also include additional benefits such as routine dental, vision or hearing services. You must have both Part A and Part B to join a Medicare Advantage plan, and you continue paying your Part B premium.

Learn more about Medicare Advantage →

Part D — Prescription Drug Coverage

Part D helps cover the cost of prescription drugs. If you have Original Medicare, you can generally add Part D through a separate Medicare drug plan. Many Medicare Advantage plans include Part D coverage within the plan. Each Part D plan has its own formulary, pharmacy network and cost structure, so the medications you take and the pharmacies you use can make a significant difference when comparing plans. Going 63 days or more without Medicare drug coverage or other creditable prescription coverage after you are eligible may result in a late-enrollment penalty.

Learn more about Part D →

Eligibility and enrollment status

Medicare eligibility depends on more than age alone. Depending on your situation, citizenship or qualifying lawful-presence status, disability or certain medical conditions, work history, and other requirements may apply. Medicare Advantage enrollment also requires Part A and Part B and residence in the plan's service area. Confirm your individual eligibility with Social Security or Medicare before enrolling.

General Enrollment Period

If you need to enroll in Part B or premium-Part A after your Initial Enrollment Period and do not qualify for a Special Enrollment Period, the General Enrollment Period runs January 1–March 31. Under current Medicare rules, coverage generally starts the month after you sign up.

How the parts fit together

Original Medicare consists of Part A and Part B. If you stay with Original Medicare, you may add a separate Part D plan for prescription coverage and may also consider Medicare Supplement Insurance (Medigap) to help with certain Part A and Part B out-of-pocket costs. Medicare Advantage, or Part C, is the other main way to receive your Medicare health coverage and usually combines Part A, Part B and Part D in one private Medicare-approved plan.

Use official cost information

Medicare costs are updated regularly. Rather than hard-code numbers that become stale, this site links to the current Medicare.gov cost page.

Original Medicare and the ACCESS Model

Beginning in 2027, some people with Original Medicare may be able to use voluntary technology-supported chronic-care services through participating organizations in Medicare's ACCESS Model. Availability depends on the condition and participating organizations, and participation does not change Original Medicare benefits or provider choice.