Original Medicare: Parts A & B

What is Original Medicare?

Original Medicare is the traditional, federally administered health insurance program run by the Centers for Medicare & Medicaid Services (CMS) for people age 65 and older, and for certain younger people with qualifying disabilities. You can learn more about the program's structure on the official Parts of Medicare page.

• Part A — Hospital insurance: inpatient hospital stays, skilled nursing facility care, hospice, and limited home health services.
• Part B — Medical insurance: doctor visits, outpatient care, preventive services, and durable medical equipment.
• With Original Medicare, you can generally see any doctor, hospital, or specialist in the United States that accepts Medicare.

How Original Medicare pays for care

For many Medicare Part B covered outpatient services, Original Medicare generally pays 80% of the Medicare-approved amount after the annual Part B deductible is met. Beneficiaries are usually responsible for the remaining 20% unless they have supplemental coverage, such as a Medicare Supplement (Medigap) policy or coverage through an employer or union. Cost-sharing for Part A inpatient care works differently and is based on deductibles and daily coinsurance amounts per benefit period.

Why Original Medicare exists

Medicare was signed into law in 1965 to protect older Americans from catastrophic medical costs. Today it covers tens of millions of Americans and remains one of the country's largest health insurance programs. Understanding its structure — and its gaps — is the first step to choosing coverage that fits your life.

The benefits of Original Medicare

• Broad nationwide access to any provider that accepts Medicare — helpful for travelers and seasonal residents.
• Freedom to see specialists without referrals in most situations.
• Government-administered coverage with standardized rules.
• A predictable structure that most U.S. providers understand.

Where Original Medicare has gaps

Original Medicare by itself does not cover everything you might expect:

• Original Medicare has no annual out-of-pocket maximum, so cost-sharing on serious illnesses can add up.
• Original Medicare generally does not cover most outpatient prescription drugs. Most beneficiaries enroll in a separate Medicare Part D prescription drug plan for this coverage.
• Original Medicare generally does not cover routine dental care, routine vision exams, eyeglasses, hearing aids, or routine hearing exams, although some medically necessary services may be covered.
• You will still owe applicable deductibles, coinsurance, and copayments unless you add supplemental coverage.
• Original Medicare generally does not cover medical care received outside the United States except in a few limited situations.

Part A vs Part B at a glance

Figures reflect the 2026 Medicare program year. Verify current numbers on Medicare.gov — Medicare costs.

What's covered vs. what's not

Who's eligible

You are generally eligible for Original Medicare at age 65 if you are a U.S. citizen or lawful permanent resident of at least five years. Younger people may qualify after 24 months of Social Security Disability Insurance (SSDI), or immediately with ALS or End-Stage Renal Disease (ESRD). Confirm your eligibility with the Social Security Administration on the official Medicare sign-up page.

Key enrollment periods

• Initial Enrollment Period (IEP): The Initial Enrollment Period lasts seven months. It begins three months before your 65th birthday month, includes your birthday month, and ends three months afterward.
• General Enrollment Period (GEP): January 1 – March 31 each year, for people who missed their IEP and do not qualify for a Special Enrollment Period.
• Special Enrollment Period (SEP): Available after certain qualifying events, such as losing employer coverage.

Full details on enrollment windows are published on the Medicare.gov "When coverage starts" page. See our enrollment timeline for a visual walkthrough.

Common mistakes to avoid

• Assuming Original Medicare covers everything — it has no annual out-of-pocket maximum and generally does not include outpatient prescription drug coverage.
• Delaying Part B while relying on retiree, COBRA, or marketplace coverage, which are generally not considered creditable and may trigger a lifetime penalty.
• Being enrolled in a Medicare Advantage plan and a Medicare Supplement (Medigap) plan at the same time — you generally cannot use both.
• Waiting past your Medicare Supplement (Medigap) Open Enrollment window, when medical underwriting may affect your rate or eligibility for certain plans.

Where Scott fits in

Most people pair Original Medicare with either a Medicare Supplement (Medigap) plan and a Part D prescription plan, or replace it with a Medicare Advantage plan. Scott will walk you through the trade-offs based on your doctors, prescriptions, and budget — without pressure. You can also compare plan options for your ZIP code any time on the Medicare.gov Plan Finder.

Frequently asked questions