Medicare Part A and Part B Explained: What They Cover and How They Work Together

Understanding Medicare Part A and Part B is one of the most important steps in making sense of Medicare as a whole. These two parts are often called “Original Medicare” and they form the foundation of most people’s Medicare coverage.

This guide breaks down what each part is, what it covers, what you pay, and how they fit into the bigger Medicare picture—so you can feel more confident about your options.

What Is Original Medicare?

Original Medicare is the traditional federal health insurance program for:

• People 65 and older, and
• Certain younger people with disabilities or specific medical conditions

Original Medicare has two main parts:

• Medicare Part A – Hospital Insurance
• Medicare Part B – Medical Insurance

Together, Part A and Part B help cover many common health care services, but not everything. You can think of them this way:

• Part A = inpatient and facility-based care
• Part B = outpatient and doctor-based care

What Is Medicare Part A? (Hospital Insurance)

Medicare Part A is often referred to as hospital insurance. It helps pay for care when you’re admitted as an inpatient to a facility.

What Medicare Part A Generally Covers

While details can vary based on the situation, Part A typically helps cover:

• Inpatient hospital stays
  • Semi-private room
  • Meals
  • General nursing care
  • Drugs and supplies you receive as an inpatient
• Skilled nursing facility (SNF) care
  • After a qualifying hospital stay, for services like rehab or specialized nursing
• Home health care (limited)
  • Part-time or intermittent skilled nursing or therapy, under specific conditions
• Hospice care
  • For people with a terminal illness who meet eligibility rules

Part A does not usually cover:

• Private-duty nursing
• Private rooms (unless medically necessary)
• Personal items like TVs or phones
• Long-term custodial care (help with daily activities only, without skilled care)

Do You Pay a Premium for Part A?

Many people qualify for “premium-free Part A” because they, or a spouse, worked and paid Medicare taxes for a certain amount of time.

You may have to pay a monthly premium for Part A if you do not have enough work history under the Medicare rules.

Even with premium-free Part A, you can still have:

• A deductible for each benefit period when you’re hospitalized
• Daily coinsurance amounts if your hospital or skilled nursing stay is long

When Does Part A Start?

For most people, Part A starts automatically at age 65 if they are already receiving Social Security or Railroad Retirement benefits. Others may need to enroll manually through Social Security when they become eligible.

What Is Medicare Part B? (Medical Insurance)

Medicare Part B is the medical insurance portion of Original Medicare. It helps cover outpatient care and doctor services, along with many preventive services.

What Medicare Part B Generally Covers

Part B typically helps pay for:

• Doctor visits (primary care and specialists)
• Outpatient services
  • Same-day surgeries
  • Diagnostic tests and imaging (like X-rays, MRIs, CT scans)
• Preventive services
  • Yearly “Wellness” visits
  • Many vaccines
  • Screenings such as mammograms, colonoscopies, and others when certain conditions are met
• Durable medical equipment (DME)
  • Items like walkers, wheelchairs, or home oxygen equipment when medically necessary
• Some home health services
  • When specific criteria are met and under a plan of care
• Certain emergency room services or urgent care when you’re not admitted as an inpatient

Part B does not cover everything. For example, it generally does not cover:

• Routine dental care
• Most vision care (like routine eye exams or eyeglasses)
• Hearing aids and fittings
• Most routine foot care

These are often covered, if at all, through separate coverage, such as Medicare Advantage plans or stand-alone insurance.

What Does Part B Cost?

Unlike Part A, almost everyone who has Part B pays a monthly premium.

With Part B, you generally face:

• A monthly premium (often deducted from Social Security benefits if you receive them)
• An annual deductible you pay first before most services are covered
• Coinsurance, often around a percentage of the Medicare-approved amount, after you meet the deductible

People with higher incomes may pay a higher Part B premium under specific income-based rules. Some people with limited income and resources may qualify for help with premiums and other costs through certain assistance programs.

Do You Have to Enroll in Part B?

Enrollment timing is important:

• Many people are automatically enrolled in Part B when they turn 65 and are already getting Social Security or Railroad Retirement benefits.
• Others must choose to enroll during their Initial Enrollment Period (a window around their 65th birthday) or during a special enrollment period if they have qualifying employer coverage.

Delaying Part B without having qualifying coverage through an employer or union health plan can lead to:

• Late enrollment penalties (usually an added amount on your monthly premium)
• Possible gaps in coverage later

Medicare Part A vs Part B: Side‑By‑Side Overview

Below is a simple comparison to see the main differences at a glance:

How Part A and Part B Work Together

Medicare Part A and Part B are designed to coordinate so that many major health needs are covered, whether you’re in the hospital or visiting a doctor.

Example: Hospital Stay and Follow-Up

1. You are admitted as an inpatient to a hospital
   • Part A helps cover your room, meals, nursing care, and related inpatient services.
2. After discharge, you see your primary care doctor or a specialist for follow-up
   • Part B helps cover those office visits and any necessary tests or imaging.
3. You need some home health services
   • Depending on the specifics, these may be covered under Part A or Part B when certain conditions are met.

Together, Parts A and B can provide a broad foundation of coverage across different settings. But they still leave some gaps, such as prescription drugs, dental, vision, and hearing in many cases.

What Original Medicare (Part A and B) Does Not Fully Cover

To understand Part A and Part B, it’s helpful to see where their limits are. Common areas that may not be fully covered include:

• Most prescription drugs you take at home
  • These are usually covered under a separate Medicare Part D plan.
• Routine dental care
  • Cleanings, fillings, dentures, and many other dental services are generally not covered.
• Routine vision and hearing services
  • Eyeglasses, contact lenses, and hearing aids are typically excluded from Original Medicare.
• Long-term custodial care
  • Ongoing help with daily activities (like bathing, dressing, or eating) when that’s the only type of care needed is usually not covered.
• Care outside the U.S. in most situations

Because of these gaps, many people add:

• A Medicare Part D prescription drug plan
• A Medicare Supplement (Medigap) policy to help with deductibles and coinsurance
• Or a Medicare Advantage (Part C) plan that combines Part A, Part B, and often Part D, and may offer extra benefits

Who Is Eligible for Medicare Part A and B?

Most people are eligible for Medicare Part A and Part B if:

• They are 65 or older and a U.S. citizen or permanent legal resident who meets residency requirements, or
• They are under 65 and meet certain disability or specific disease criteria

Eligibility determines whether:

• You qualify for premium-free Part A, and
• How you enroll in both Part A and Part B

People who do not qualify for premium-free Part A may still be able to buy Part A and enroll in Part B, as long as they meet other eligibility rules.

When and How to Enroll in Medicare Part A and B

Understanding enrollment periods can help you avoid gaps and penalties.

Initial Enrollment Period (IEP)

Your Initial Enrollment Period is a 7-month window:

• It starts 3 months before the month you turn 65
• Includes your birthday month
• Ends 3 months after your birthday month

During this time, you can:

• Enroll in Part A
• Enroll in Part B
• Decide if you want additional coverage such as Part D or a Medicare Advantage plan

Special Enrollment Period (SEP)

You may qualify for a Special Enrollment Period if you:

• Have employer or union coverage based on current work (your own or a spouse’s) when you’re first eligible for Medicare, and
• Choose to delay Part B because of that coverage

When that employer or union coverage ends, you usually have a limited time to sign up for Part B without a late penalty.

General Enrollment Period (GEP)

If you miss your IEP and do not qualify for a SEP, you may need to wait for the General Enrollment Period, which occurs once a year under current rules. Enrolling during this time can lead to:

• Delayed coverage start dates
• Possible late enrollment penalties added to your premium

What You Pay Under Part A and Part B

While you rarely pay the full cost of services under Original Medicare, you typically share costs with the program.

Under Part A, you may pay:

• A deductible for each benefit period when you’re admitted to the hospital
• Daily coinsurance if you stay in a hospital or skilled nursing facility beyond certain day limits

Under Part B, you may pay:

• A monthly premium
• An annual deductible
• Coinsurance, often a percentage of the Medicare-approved amount for most services after you meet your deductible

You may choose to add:

• Medigap (Medicare Supplement) coverage, which can help pay some of these out-of-pocket costs, or
• A Medicare Advantage plan, which has its own cost structure and rules

How to Decide if Part A and B Alone Are Enough

Original Medicare (Part A and B) is the starting point, but many people ask whether it’s enough by itself. Consider:

• Your health needs
  • Do you see doctors often? Need specialty care?
• Prescription drugs
  • Do you take medications regularly that would require a Part D plan?
• Budget and risk tolerance
  • Are you comfortable with deductibles, coinsurance, and the lack of an overall out-of-pocket maximum in Original Medicare?
• Extra benefits
  • Do you want coverage for things like routine dental, vision, or hearing that Original Medicare generally does not cover?

Many people keep Part A and Part B as their base coverage and then:

• Add a Part D drug plan and Medigap policy, or
• Choose a Medicare Advantage (Part C) plan as an alternative way to receive their Part A and B benefits through a private plan, often with extra features

Key Takeaways About Medicare Part A and Part B

Here’s a concise recap to keep the main points clear:

• Medicare Part A is hospital insurance

  • Helps cover inpatient hospital care, skilled nursing facility care, some home health care, and hospice
  • Often premium-free if you or a spouse worked and paid Medicare taxes long enough

• Medicare Part B is medical insurance

  • Helps cover doctor visits, outpatient care, preventive services, and durable medical equipment
  • Comes with a monthly premium, annual deductible, and coinsurance

• Together, Part A and B = Original Medicare

  • They form your core Medicare coverage
  • They do not typically include routine dental, vision, or hearing, and don’t usually cover most drugs you take at home

• Most people add coverage

  • Many choose Part D for prescriptions and may add Medigap or enroll in a Medicare Advantage plan for broader protection

Understanding what Medicare Part A and Part B are—and what they are not—gives you a solid foundation for exploring your next steps, comparing options, and choosing the coverage that best fits your needs and budget.