Medicare Part B Explained: Everything You Need to Know About Medical Insurance (2025)

If Part A is your safety net for hospital stays, Part B is your everyday workhorse. It covers doctor visits, outpatient care, preventive services, lab tests, medical equipment, and so much more.

But Part B is also where things get complicated. You pay a monthly premium, a yearly deductible, and 20% coinsurance with no out-of-pocket limit. Unlike Part A, which most people get for free, Part B costs money—and those costs can add up fast.

Let's break down exactly what Part B covers, what it costs in 2025, and how to avoid expensive surprises.

What Is Medicare Part B?

Part B is medical insurance that covers:

• Doctor services and outpatient care
• Preventive services and screenings
• Medically necessary services and supplies
• Durable medical equipment (DME)
• Some medications (administered by a doctor, not picked up at a pharmacy)

Think of Part B as covering everything that's not a hospital inpatient stay—your doctor visits, tests, imaging, therapy, equipment, and preventive care.

What Part B Covers (in Detail)

1. Doctor Services

Part B covers visits to:

• Primary care doctors
• Specialists
• Surgeons (for consultations and follow-ups)
• Doctors who see you while you're hospitalized (even though the hospital stay itself is Part A)

This includes:

• Office visits
• Home visits (when medically necessary)
• Second opinions
• Surgical consultations

Your Cost: After you meet the annual deductible, you pay 20% of the Medicare-approved amount.

2. Outpatient Care

Part B covers medical services you receive without being admitted to a hospital:

• Outpatient surgery
• Emergency department visits (if you're not admitted)
• Observation care (even if you spend the night)
• Outpatient hospital services (injections, X-rays, tests)
• Ambulance services (when medically necessary)
• Outpatient mental health services

3. Preventive Services

One of the best benefits of Part B is that many preventive services are 100% covered—no deductible, no coinsurance.

Free Preventive Services (no cost to you):

• Annual Wellness Visit
• Welcome to Medicare Visit
• Abdominal aortic aneurysm screening
• Alcohol misuse screening
• Bone mass measurement
• Cardiovascular disease screening
• Cardiovascular behavioral therapy
• Cervical and vaginal cancer screening
• Colorectal cancer screenings
• Depression screening
• Diabetes screening and self-management training
• Hepatitis B and C screening
• HIV screening
• Lung cancer screening
• Mammograms (every 12 months)
• Obesity screening and counseling
• Prostate cancer screening (PSA test)
• STI screening and counseling
• Tobacco cessation counseling
• Vaccines: flu, pneumonia, Hepatitis B, COVID-19

4. Lab Tests and Diagnostic Services

Part B covers:

• Blood tests
• Urinalysis
• X-rays
• MRIs, CT scans, PET scans
• Ultrasounds
• EKGs and cardiac tests
• Biopsies

Your Cost: 20% coinsurance after deductible (unless preventive).

5. Outpatient Mental Health Services

Part B covers:

• Psychiatrists
• Psychologists
• Clinical social workers
• Psychiatric nurse specialists
• Individual and group therapy
• Family therapy (when focused on the patient's treatment)
• Diagnostic psychiatric evaluations
• Partial hospitalization (intensive outpatient program)

Your Cost: 20% coinsurance after deductible.

6. Durable Medical Equipment (DME)

Part B covers equipment that is:

• Ordered by a doctor
• Medically necessary
• Used in your home

Examples:

• Wheelchairs and scooters
• Walkers and canes
• Hospital beds
• Oxygen equipment
• Nebulizers and respiratory equipment
• Blood sugar monitors/test strips
• CPAP machines
• Prosthetic limbs
• Braces and orthotics
• Breast prostheses after mastectomy

Your Cost: 20% coinsurance after deductible.

7. Physical, Occupational, and Speech Therapy

Part B covers therapy when it is:

• Ordered by a doctor
• Medically necessary
• Provided by Medicare-certified therapists

Therapy Caps: There are no hard caps, but Medicare has "thresholds" requiring extra documentation for high-cost therapy.

Your Cost: 20% after deductible.

8. Limited Outpatient Prescription Drugs

Part B covers certain prescription drugs, but only if administered by a doctor or in a clinical setting.

Examples:

• Chemotherapy drugs
• Certain dialysis medications
• Injectables for osteoporosis
• Immunosuppressants after transplant
• Blood clotting factors (hemophilia)
• Certain vaccines

Your Cost: 20% after deductible.

9. Home Health Care (Part B)

Most home health care is covered under Part B, NOT Part A.

Requirements:

• You're homebound
• You need intermittent skilled nursing or therapy
• A doctor orders and reviews care
• The agency is Medicare-certified

Covered:

• Skilled nursing
• PT, OT, Speech Therapy
• Medical social services
• Limited home health aide services (only alongside skilled care)

Cost: $0 for covered services.

Not Covered:

• 24-hour care
• Meals
• Homemaker tasks
• Personal care without skilled services

10. Ambulance Services

Part B covers ambulance transportation when:

• It's medically necessary
• Other transportation would endanger your health
• You're taken to the nearest appropriate facility

Covered:

• Emergency ambulance
• Air ambulance
• Non-emergency ambulance (only when medically necessary)

Your Cost: 20% after deductible.

What Part B Does NOT Cover

• Routine dental care
• Routine eye exams (except certain conditions)
• Eyeglasses or contacts (except after cataract surgery)
• Hearing aids
• Routine foot care (except for diabetes-related issues)
• Cosmetic surgery
• Acupuncture (except chronic low back pain)
• Long-term custodial care
• Most pharmacy prescriptions (requires Part D)
• Care outside the U.S. (limited exceptions)

What Part B Costs in 2025

Monthly Premium

Standard Premium: $185.00/month

Premiums increase for higher earners (IRMAA):

Deductible (2025)

$257 per year.

Coinsurance

After deductible, Medicare pays 80% and you pay 20% of the Medicare-approved amount.

There is no out-of-pocket maximum with Original Medicare.

Medicare Assignment

Doctors who accept Medicare assignment:

• Accept Medicare's approved amount as full payment
• Cannot bill more than the 20% coinsurance
• Bill Medicare directly

Doctors who do NOT accept assignment:

• Can charge up to 15% more (Part B excess charge)
• You may pay upfront
• You handle reimbursement

Real-World Cost Examples

This is why Medigap or Medicare Advantage is important.

How to Protect Yourself from High Part B Costs

1. Medigap

Plan G covers:

• Part B coinsurance (20%)
• Excess charges
• Part A deductible
• Does NOT cover Part B deductible

Plan N covers:

• Part B coinsurance (with small copays)
• Does NOT cover Part B deductible or excess charges

2. Medicare Advantage

Pros: Out-of-pocket maximum, low premiums

Cons: Network restrictions

3. Always Confirm Medicare Assignment

Ask every time: "Do you accept Medicare assignment?"

4. Use Preventive Services

Preventive care is free when billed as preventive.

Common Part B Questions

The Bottom Line

Part B is essential for doctor visits, outpatient care, preventive services, imaging, and medical equipment. But the 20% coinsurance with no cap can expose you to high costs.