Medicare Insurance Explained: Coverage, Enrollment, Benefits, and Costs

What is Medicare?

Federal health insurance for adults 65 and older and qualifying individuals with disabilities, Medicare was established by Congress in 1965 under the Social Security Act. The program is designed to pay part of your hospital and medical bills, not all of them. According to the Centers for Medicare & Medicaid Services (CMS), the program currently serves more than 67 million Americans nationwide.

Types of Medicare

1. Medicare Part A.

Services offered:

> Hospice care. After the provider certifies that you are terminally ill, they offer this care. The Medicare hospice benefit includes pain management, counseling, and support services for both the patient and family members.

> Home health care. The care is extended in your home if you are homebound and need skilled care. You receive 100 days of daily care or intermittent without amount. To qualify, you must have been an inpatient and have spent at least three consecutive days, with a range of 14 days of receiving home healthcare. The CMS home health guidelines outline specific eligibility criteria that your physician must certify.

> Inpatient hospital care. This is the care you receive when you are officially admitted to the hospital by a physician. You receive a 90-day cover in a general hospital and 190 lifetime days in a Medicare-certified psychiatric hospital. The inpatient deductible under Part A is $1,676 per benefit period.

> Skilled nursing facility (SNF) care. It covers a room and board provided by an SNF, like being fed using tubes and wound care. The care takes up to 100 days upon qualifying for the cover, according to Medicare.gov’s SNF coverage page.

Part A is often misunderstood as fully free. While most enrollees pay no premium for Part A, the benefit period deductibles and coinsurance costs can add up significantly if a beneficiary experiences multiple hospitalizations in a single year. This is a real financial exposure that Original Medicare does not cap, which is one reason many beneficiaries pair Part A with a Medigap policy or move to Medicare Advantage, per CMS guidance on Medigap.

2. Medicare Part B

> Ambulance services. This is emergency transportation, basically from the hospital. Coverage for non-emergency transit is limited to instances in which no safe substitute means are available and where it is medically essential. The Medicare ambulance benefit is administered under Part B and subject to the annual Part B deductible of $257.

> Durable Medical Equipment (DME).

These are pieces of equipment that can be used over and over and at home for medical purposes. They include oxygen tanks and wheelchairs. According to the CMS DME Center, Medicare covers 80% of the approved amount for DME after the deductible is met, leaving the beneficiary responsible for the remaining 20%.

> Preventive services.

These services are intended to reduce illness and detect conditions early. They include screening and counseling, and coinsurance generally does not apply. Preventive screenings covered by Part B include mammograms, colonoscopies, cardiovascular screenings, and diabetes tests, as outlined by Medicare.gov’s preventive services directory.

> Therapy services. A Medicare-certified therapist gives outpatient speech and occupational therapy. Physical therapy is also covered under Part B, subject to annual limits reviewed and updated by CMS each year.

> Chiropractic care. It involves fixing the spine when one or more of the bones move from their original positions. Part B covers chiropractic manipulation of the spine only, and does not cover maintenance therapy or other chiropractic services.

Medicare Part	What It Covers	2025 Premium	2025 Deductible	Who Pays Premium
Part A (Hospital Insurance)	Inpatient hospital, SNF, hospice, home health	$0 for most enrollees	$1,676 per benefit period	Most enrollees pay $0 if they worked 40+ quarters
Part B (Medical Insurance)	Outpatient care, DME, preventive services	$185.00/month	$257/year	All Part B enrollees
Part C (Medicare Advantage)	Combines Parts A, B; often includes Part D	Varies by plan (avg. $17/month)	Varies by plan	Enrollee pays plan premium + Part B premium
Part D (Prescription Drugs)	Outpatient prescription medications	Varies by plan (avg. $46.50/month)	Up to $590/year	All Part D enrollees

3. Part C offers an alternative way of getting Medicare Advantage.

Types of Medicare Advantage plan

> Health maintenance organization.

>Private Fee-for-service.

>Preferred provider organization.

>Medicare savings accounts.

>Special needs plan.

> Provider sponsored organization.

The Medicare Advantage Plan applies different rules, restrictions, and costs, affecting when and how you receive care. Under this plan, you can have additional benefits not available in Original Medicare, like training, caregiver counseling, and dental and vision care. The plan may have different premiums besides the Part B premiums, a network of providers, and cost-sharing for covered services. According to the Kaiser Family Foundation (KFF), more than 54% of all Medicare beneficiaries were enrolled in a Medicare Advantage plan as of 2025, with major carriers including UnitedHealthcare, Humana, and CVS Health’s Aetna dominating enrollment. The CMS Medicare Advantage rate data shows continued growth in plan availability across most U.S. counties.

That growth comes with a caution, though. Medicare Advantage plans can offer attractive extra benefits, but beneficiaries must carefully compare network restrictions and prior authorization requirements each year during Open Enrollment, because plans can change significantly from one year to the next. The National Council on Aging (NCOA) recommends reviewing your plan’s Summary of Benefits annually rather than assuming your current coverage stays the same.

> Part D

Covering most outpatient prescription drugs, Part D is offered through a private company as a set of benefits included with the Medicare Advantage Plan or for those enrolled in Original Medicare. The Medicare Part D program was created by the Medicare Modernization Act of 2003 and first took effect in 2006.

Part D coverage

Part D uses a list of covered drugs called a formulary. If your drug is missing from this list, you should request an exception, pay out of your pocket, or file an appeal. The Medicare.gov Part D formulary guidelines explain your rights when a drug is not covered.

>Immunosuppressant drugs, anticonvulsive treatment for seizure disorders. Part D must also cover vaccines and exclude those covered in Part B. The Inflation Reduction Act capped out-of-pocket prescription drug costs for Part D enrollees at $2,000 per year starting in 2025, a major change administered by CMS under the Inflation Reduction Act.

Factors that affect original Medicare out-of-pocket costs

> Where your doctor and you or other healthcare providers sign a private contract.

>If you have other health insurance that can work together with Medicare, such as employer coverage, retiree coverage, or a Medigap supplemental policy issued by a private insurer like Mutual of Omaha or AARP/UnitedHealthcare.

> What type of healthcare do you require, and how often do you need it?

>Whether you have Part A and Part B or both.

> Medigap policy enrollment. Medigap (Medicare Supplement Insurance) policies are standardized by CMS and regulated at the state level. These plans help cover deductibles, coinsurance, and copayments left over by Original Medicare.

> Your decision on getting services or supplies Medicare doesn’t cover. If you choose this, you pay all the cost unless you have other insurance coverage to handle it.

Enrolling in Medicare

Open enrollment matters because coverage options, plan premiums, and provider networks change year to year. Anyone who delays enrolling without a qualifying reason faces permanent penalties. The Social Security Administration (SSA) manages the initial enrollment process for Medicare Parts A and B.

– Automatic initial enrollment

For Parts A and B, you can be automatically enrolled for your initial enrollment or do it yourself. Automatic enrollment applies if you are under 65 years and disabled and have benefited from disability for not less than two years, if you are already receiving Social Security benefits, in case you have Amyotrophic Lateral Sclerosis (ALS), and you have been benefiting from the Railroad Retirement Board (RRB). The SSA Medicare enrollment page outlines each of these automatic eligibility pathways in detail.

– Non-automatic initial enrollment

You cannot be automatically enrolled if you are not receiving Social Security benefits, Railroad Retirement Board benefits, or have end-stage renal disease (ESRD) and yet turn 65. In these cases, you must actively sign up through the SSA online portal or at your local Social Security office within your Initial Enrollment Period (IEP), which spans a 7-month window around your 65th birthday.

Special Enrollment Related to Coverage under Group Health Plans

This is a chance given to people who never signed up for Medicare when first eligible due to active coverage from current employment. In this case, you may choose coverage to begin on the month you sign up or at the start of any of the three months upon signing up. The Medicare Special Enrollment Period (SEP) rules are governed by CMS and the SSA and are designed to prevent gaps in coverage for working individuals and their dependents.

Advantages of Medicare.

> There are $0 premium plans available.

>Provides lower premiums than those on Medicare Supplement and prescription drug cover.

> No restrictions even if you have a pre-existing condition for the acceptance is obvious.

> Out-of-pocket costs are lower than Original Medicare.

Disadvantages of Medicare

> The insured are mandated to pay for services outside the provider network fully.

> Changes to the plan may occur annually.

> Copayments and deductibles are a member’s responsibility.

> The doctors may not accept any other hospital/doctors and may also make a strong choice for the Medicare Advantage Plans you previously had.

> May attract referrals for appointments with a specialist.

> You may not be covered if you live in two different places during one year.

For most older adults and people with disabilities, the value of having structured coverage outweighs these drawbacks. That said, no single part of Medicare covers everything, and choosing between Original Medicare, Medicare Advantage, and Medigap requires comparing your specific health needs, budget, and preferred doctors. You can use the Medicare Plan Finder tool on Medicare.gov to compare available plans in your area and find the best fit for your needs.

Frequently Asked Questions

What is Medicare and who qualifies for it?

Medicare is a federal health insurance program administered by the Centers for Medicare & Medicaid Services (CMS) that covers Americans aged 65 and older, individuals under 65 with qualifying disabilities, and people with end-stage renal disease (ESRD) or ALS. Most people qualify for premium-free Part A if they or their spouse worked and paid Medicare taxes for at least 10 years (40 quarters).

What is the difference between Medicare Part A and Part B?

Part A covers inpatient hospital care, skilled nursing facility stays, hospice, and home health care. Part B covers outpatient medical services, preventive care, durable medical equipment (DME), and ambulance services. Together, Parts A and B make up what is called Original Medicare.

How much does Medicare cost in 2025?

The standard Part B premium is $185.00 per month, and the Part B annual deductible is $257. The Part A inpatient hospital deductible is $1,676 per benefit period. Most enrollees pay no premium for Part A if they worked at least 40 quarters. Higher-income beneficiaries pay more through the Income-Related Monthly Adjustment Amount (IRMAA), calculated by the Social Security Administration.

What is Medicare Advantage (Part C)?

Medicare Advantage is an alternative to Original Medicare offered by private insurers approved by CMS. These plans must cover everything Original Medicare covers but often include additional benefits like dental, vision, and hearing. Over 54% of Medicare beneficiaries were enrolled in Medicare Advantage as of 2025, according to the Kaiser Family Foundation. Major insurers offering these plans include UnitedHealthcare, Humana, and Aetna.

What does Medicare Part D cover?

Part D covers outpatient prescription drugs through a list called a formulary. Each plan’s formulary is different, and coverage is provided through private insurers. Starting in 2025, the Inflation Reduction Act capped annual out-of-pocket drug costs for Part D enrollees at $2,000 per year. If your drug is not on the formulary, you may file an exception or appeal with your plan.

When should I enroll in Medicare?

Your Initial Enrollment Period (IEP) is a 7-month window: 3 months before, the month of, and 3 months after your 65th birthday. If you miss this window without qualifying for a Special Enrollment Period (SEP), you may face permanent late enrollment penalties. The Social Security Administration manages Medicare enrollment and can be reached at SSA.gov.

What is the Medicare late enrollment penalty?

If you delay enrolling in Part B without qualifying employer coverage, your monthly premium increases by 10% for each full 12-month period you were eligible but did not enroll. This penalty is permanent and added to your Part B premium for as long as you have Part B. A similar late enrollment penalty applies to Part D.

What is Medigap and how does it work with Medicare?

Medigap (Medicare Supplement Insurance) is private insurance that helps cover out-of-pocket costs not paid by Original Medicare, including deductibles, coinsurance, and copayments. Medigap plans are standardized by CMS and labeled by letter (Plan G, Plan N, etc.). You must have both Part A and Part B to purchase a Medigap policy. You cannot have both a Medigap policy and a Medicare Advantage plan simultaneously.

Can I have Medicare and Medicaid at the same time?

Yes. Individuals who qualify for both Medicare and Medicaid are called dual eligibles. Medicaid, administered jointly by the federal government and states, may cover Medicare premiums, deductibles, and copayments for qualifying low-income individuals. Approximately 12 million Americans are dual-eligible, according to Medicaid.gov.

What is not covered by Medicare?

Original Medicare does not cover most dental care, routine vision, hearing aids, long-term custodial care, or care received outside the United States. Some Medicare Advantage (Part C) plans offered by private insurers like UnitedHealthcare, Humana, and Aetna do include dental, vision, and hearing benefits. For coverage gaps, enrollees may consider a Medigap policy or, where eligible, Medicaid assistance.

Does Medicare cover prescription drugs automatically?

No. Prescription drug coverage through Part D is not automatic; you must actively enroll in a standalone Part D plan or choose a Medicare Advantage plan that includes drug coverage. Failing to enroll when first eligible results in a permanent late enrollment penalty added to your monthly Part D premium. The Medicare.gov Part D page explains enrollment windows and how to compare plans by formulary.

What is IRMAA and who pays it?

IRMAA stands for Income-Related Monthly Adjustment Amount. Higher-income Medicare beneficiaries pay a surcharge on top of the standard Part B premium of $185.00 and their Part D premium. The Social Security Administration calculates IRMAA using your tax return from two years prior. For 2025, IRMAA surcharges begin for individuals with modified adjusted gross income above $106,000, per CMS guidelines.

Is Medicare the same as Medicaid?

No. Medicare is a federal program based on age or disability status and is administered by CMS. Medicaid is a joint federal-state program based on income and financial need, with eligibility rules that vary by state. The two programs can work together for dual-eligible individuals, but they have separate enrollment processes, benefit structures, and governing rules.