Medicare is the federal health insurance program for Americans aged 65 and older, as well as certain younger individuals with disabilities. Learn everything you need to know about coverage, plan types, and enrollment.
65M+
Americans enrolled
4
Coverage parts
1965
Year established
Overview
Medicare is a federal health insurance program administered by the Centers for Medicare & Medicaid Services (CMS). It was signed into law in 1965 as part of the Social Security Act and has since grown into one of the largest health coverage programs in the United States.
The program is funded through payroll taxes, premiums paid by beneficiaries, and general federal revenue. Medicare does not cover all health care costs, so many beneficiaries choose supplemental coverage to help with out-of-pocket expenses.
Medicare is divided into different parts, each covering specific types of health care services. Understanding what each part covers helps beneficiaries make informed decisions about their healthcare.
Inpatient hospital stays, skilled nursing, and hospice care.
Doctor visits, outpatient care, and preventive services.
Coverage for prescription medications through Part D.
Alternative bundled plans offered by private insurers.
Coverage
Medicare is divided into four distinct parts, each designed to cover different aspects of healthcare.
Covers inpatient hospital care, skilled nursing facility care, hospice care, and some home health services.
Typical Cost
Premium-free for most people who paid Medicare taxes for at least 10 years.
Covers outpatient care, doctor visits, preventive services, and medical supplies needed to treat health conditions.
Typical Cost
Standard monthly premium applies. Amount may vary based on income.
An alternative way to get Medicare benefits through private insurance companies approved by Medicare, often including additional benefits.
Typical Cost
Costs vary by plan and insurer. You still pay your Part B premium.
Adds prescription drug coverage to Original Medicare (Parts A & B) and is available through Medicare-approved private companies.
Typical Cost
Monthly premiums vary by plan. Available as a standalone plan or bundled with Part C.
Who Qualifies
Medicare eligibility is based on age, citizenship status, and in some cases, disability or health conditions.
U.S. citizens and permanent legal residents who are 65 years of age or older are generally eligible for Medicare, provided they or their spouse have worked and paid Medicare taxes for at least 10 years (40 quarters).
Individuals under 65 may be eligible if they have received Social Security Disability Insurance (SSDI) benefits for at least 24 months, or if they have been diagnosed with End-Stage Renal Disease (ESRD) or ALS.
People of any age with End-Stage Renal Disease (permanent kidney failure requiring dialysis or a transplant) or Amyotrophic Lateral Sclerosis (ALS, also known as Lou Gehrig's disease) can qualify for Medicare regardless of age.
Citizenship & Residency Requirement
To be eligible for premium-free Medicare Part A, you must be a U.S. citizen or a permanent legal resident who has lived in the United States for at least 5 consecutive years. You may still be able to purchase Medicare coverage if you don't meet these requirements.
Timing
Enrolling in Medicare at the right time can affect your premiums and coverage start dates. Missing deadlines may result in late enrollment penalties.
A 7-month window that begins 3 months before the month you turn 65, includes your birthday month, and ends 3 months after.
7-month window around your 65th birthday
If you missed your Initial Enrollment Period, you may sign up between January 1 and March 31 each year. Coverage begins July 1.
January 1 – March 31 annually
Triggered by qualifying life events such as losing employer coverage, moving, or changes in Medicaid eligibility. Usually lasts 2–3 months.
Triggered by qualifying life events
Each fall, from October 15 to December 7, you can switch between Original Medicare and Medicare Advantage, or change your Part D drug plan.
October 15 – December 7 annually
From January 1 to March 31, current Medicare Advantage enrollees can switch to a different MA plan or return to Original Medicare and add a Part D plan.
January 1 – March 31 for MA enrollees
Failing to enroll in Part B or Part D when first eligible may result in a permanent premium surcharge added to your monthly costs for as long as you have Medicare.
Penalties may be permanent — enroll on time
Medicare is a federal program primarily for people 65 and older, funded through payroll taxes and premiums. Medicaid is a joint federal-state program designed for people with limited income and resources, available at any age. Some people qualify for both programs simultaneously — they are known as "dual eligibles."
Original Medicare (Parts A and B) generally does not cover routine dental, vision, or hearing care. However, some Medicare Advantage (Part C) plans may include these benefits. It's important to review individual plan details to understand what is and isn't included.
With Original Medicare, you can typically see any doctor who accepts Medicare across the country. Medicare Advantage plans may have specific networks of doctors and hospitals. If keeping your current doctor is a priority, it's important to verify their network participation before selecting a plan.
Medigap is supplemental insurance sold by private companies to cover gaps in Original Medicare, such as copayments, coinsurance, and deductibles. Medigap policies only work alongside Original Medicare — they cannot be combined with Medicare Advantage plans. Several standardized plan types are available.
In most cases, Original Medicare does not cover healthcare services received outside the United States. There are a few limited exceptions, such as emergencies near the U.S.-Canada or U.S.-Mexico border. Some Medigap plans offer limited foreign travel emergency coverage.
You can apply for Medicare through the Social Security Administration — online at ssa.gov, by calling their toll-free number, or by visiting a local Social Security office. If you are already receiving Social Security benefits when you turn 65, you will typically be enrolled in Medicare Parts A and B automatically.
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