Medicare Part B

What is Medicare Part B

Medicare Part B is the portion of Medicare that covers outpatient medical services. It helps pay for doctor visits, preventive care (like screenings and vaccines), lab tests, outpatient hospital services, durable medical equipment, and some home health and mental health care. After paying a monthly premium and meeting a small annual deductible, beneficiaries usually pay 20% of the Medicare-approved cost for most services, while Medicare pays the rest. Part B does not cover routine dental, vision, or hearing, most prescription drugs, or long-term custodial care. Enrollment is generally at age 65 unless you qualify earlier through disability, and late enrollment can result in a penalty.

Table of Contents:

Medicare Part B Coverage

Covered Medical Services under Medicare Part B
These are services or supplies needed to diagnose or treat a medical condition that meet accepted medical standards.

Doctor and specialist visits.
Outpatient care and procedures.
Diagnostic tests (X-rays, lab tests, MRIs, CT scans).
Outpatient surgeries.
Ambulance services (emergency and some non-emergency).
Durable medical equipment (DME) such as wheelchairs, walkers, oxygen equipment.
Mental health care (outpatient and partial hospitalization).
Home health services (if not covered under Part A).
Certain prescription drugs administered in a clinical setting (e.g., injections or infusions).

Covered Preventive Services Under Medicare Part B
Preventive services help detect illness early or manage risk factors. Most preventive services are covered at no cost if you see a provider who accepts Medicare assignment.

Examples include:

Annual “Welcome to Medicare” and Yearly Wellness Visits.
Flu, COVID-19, hepatitis B, pneumonia vaccines.
Screenings for cancer (breast, colorectal, prostate, cervical), diabetes, and cardiovascular disease.
Bone density tests.
Depression, alcohol misuse, and tobacco use counseling.
Obesity counseling and nutrition therapy.
HIV, STD, and hepatitis C screenings.

Non-Covered Services under Medicare Part B
Part B does not pay for everything. Common exclusions include:

Most dental care, dentures, and routine oral exams.
Routine vision exams and eyeglasses (except after cataract surgery).
Hearing exams and hearing aids.
Cosmetic surgery.
Routine foot care.
Acupuncture (except for chronic low back pain under certain limits).
Long-term custodial care or personal care services.
Prescription drugs you take at home (covered by Part D).

Medicare Part B Eligibility

Age 65 or older:
You are eligible if you are a U.S. citizen or a permanent legal resident who has lived in the U.S. for at least 5 continuous years.

Those individuals who are under 65:
You may qualify if you have:

Been entitled to Social Security Disability Insurance (SSDI) benefits for 24 months.
Been diagnosed with End-Stage Renal Disease (ESRD) requiring dialysis or a kidney transplant.
Been diagnosed with Amyotrophic Lateral Sclerosis (ALS/Lou Gehrig’s disease) — in which case Medicare Part B starts the same month your disability benefits begin.

Medicare Part B Premium Cost

How much does Part B Cost?

Almost everyone pays a monthly premium for Part B. If you delay enrollment without having creditable coverage (e.g., employer coverage), you may face a permanent late enrollment penalty added to your premium. For 2025, the standard monthly premium for Medicare Part B is $185.00.

However, higher-income beneficiaries may pay an additional surcharge known as IRMAA (Income-Related Monthly Adjustment Amount).

Medicare Part B Income-Related Monthly Adjustment Amount (IRMAA)
The Income-Related Monthly Adjustment Amount (IRMAA) is an extra charge added to your monthly Medicare Part B premium if your income is above certain thresholds. It’s based on your Modified Adjusted Gross Income (MAGI) from your IRS tax return two years prior (e.g., 2023 income is used for 2025 premiums).

Who pays it: Higher-income beneficiaries (above $103,000 individual or $206,000 joint in 2025).
How it works: Social Security or the Railroad Retirement Board checks IRS data each year and notifies you if you owe IRMAA.
Billing: Added directly to your Part B premium; deducted from your Social Security check or billed if you don’t receive benefits.
Adjustments: The surcharge is recalculated yearly. You can appeal if your income has dropped due to a life-changing event (like retirement, marriage/divorce, or death of a spouse) using Form SSA-44.
Duration: IRMAA applies as long as your income stays above the thresholds; it falls off if your income decreases in later years.

IRMAA makes higher earners pay more for Part B (and Part D), and it’s reviewed every year based on IRS-reported income.

Below is the 2025 Medicare Part B IRMAA (Income-Related Monthly Adjustment Amount) table:

Individual Income in Year 2023	Joint Income in Year 2023	2025 Part B Monthly Premium
$0 – $106,000	$0 – $212,000	$185.00 (standard premium)
$106,001 – $133,000	$212,001–$266,000	$259.00
$133,001 – $167,000	$266,001–$344,000	$370.00
$167,001 – $200,000	$344,001–$400,000	$480.90
$200,001 – $500,000	$400,001–$750,000	$591.90
$500,000 or more	$750,001 or more	$628.90

Part B Late Enrollment Penalty

If you don’t sign up for Part B when first eligible and don’t have creditable coverage, you’ll pay a 10% penalty for each 12-month period you could’ve had Part B but didn’t.

Penalty Formula:
(10% × Number of 12-month periods delayed) × Standard Premium

This penalty lasts for as long as you have Part B.

Example:
If you delayed Part B for 3 years without creditable coverage:
10% × 3 = 30% penalty → You’ll pay 30% more on your monthly premium every month for life.

Medicare Part B Cost-Share

Annual deductible (you pay this first each year). The Part B deductible for 2025 is $257.
20% coinsurance for most covered services after the deductible (Medicare pays ~80%).
$0 for many preventive services when provider accepts assignment.
Possible excess charges if a doctor doesn’t accept assignment (varies by state/plan).

When to Enroll in Medicare Part B

You generally enroll in Medicare Part A and/or Part B during your Initial Enrollment Period (IEP)—a 7-month window spanning the 3 months before your 65th-birthday month, your birthday month, and 3 months after. If you enroll before your birthday month, coverage starts the first day of your birthday month (the month before if your birthday is on the 1st); if you enroll during or after, coverage starts the first day of the month after you enroll. If you’re still covered by active employer/union group health insurance (yours or your spouse’s), you may delay and later use a Special Enrollment Period (SEP)—an 8-month window that begins the month after employment or that coverage ends—to sign up without a late penalty. If you miss both IEP and SEP, you can enroll during the General Enrollment Period (GEP) (Jan 1–Mar 31 each year), with coverage beginning the first day of the month after you enroll and possible late-enrollment penalties. Premium-free Part A can be retroactive up to 6 months (not before you’re eligible); Part B is never retroactive.

Who qualifies:
Your Initial Enrollment Period (IEP) is your first chance to sign up for Medicare when you become eligible — usually when you turn 65 (or after 24 months of disability benefits).

When You Can Enroll:
Your IEP is a 7-month window that includes:

3 months before your 65th birthday month.
Your birthday month.
3 months after your birthday month.

During this period, you can enroll in:

Medicare Part A (Hospital Insurance).
Medicare Part B (Medical Insurance).
Medicare Advantage (Part C).
Prescription Drug Plan (Part D).

When Coverage Begins:

Enroll before your birthday month: Coverage starts the first day of your birthday month.
(If your birthday is on the 1st, coverage starts the month before.)
Enroll during your birthday month: Coverage starts the first day of the following month.
Enroll 1–3 months after your birthday month: Coverage starts the first day of the month after you enroll.

Example:
If your 65th birthday is July 20:

Enroll in April, May, or June → coverage begins July 1.
Enroll in July → coverage begins August 1.
Enroll in August → coverage begins September 1.
Enroll in September → coverage begins October 1.

Who qualifies:
You may use this SEP if you delayed enrolling in Medicare Part A and/or Part B because you (or your spouse) were covered under an employer or union group health plan.
When that coverage ends, you get a Special Enrollment Period to sign up without penalty.

When You Can Enroll:
The SEP lasts for 8 months starting the month after your employer or union coverage ends, or the month after your employment ends — whichever happens first.

You can choose to enroll in:

Medicare Part A (Hospital Insurance).
Medicare Part B (Medical Insurance).
And, if desired, a Medicare Advantage (Part C) or Prescription Drug Plan (Part D) once your Parts A & B are active.

When Coverage Begins:

Coverage generally starts the first day of the month after your plan or Social Security office receives your enrollment request.
You can request an earlier start date (retroactive up to 6 months) for Part A only — but not before you’re eligible for Medicare.
For Part B (and any Part C or D plans you choose), coverage always begins the first of the month after enrollment.

Example:

If your employer coverage ends April 30, your SEP runs from May 1 through December 31.
If you enroll in Part B in June, your Medicare coverage starts July 1.

What it is:
If you missed your IEP and don’t qualify for a SEP, you can sign up for Medicare Part A and/or Part B each year Jan 1 – Mar 31. Your coverage begins the 1st of the month after you enroll.

What you can do during GEP:

Enroll in Part A and/or Part B (late penalties may apply if you lacked creditable coverage).
Medicare.
After A/B are active, you may join Medicare Advantage (Part C) plan, or Prescription Drug Plan (Part D).

Plan coverage generally starts the 1st of the month after the plan gets your request.

Part D timing after GEP (important):
If you enroll in premium Part A and/or Part B during GEP, you get a Part D SEP that begins when you apply for A or B and lasts through the first 2 months of your A/B enrollment—so you can add Part D without waiting for AEP. (Coverage begins the 1st of the month after the Part D plan receives your request.)

Coverage start examples:

Enroll in Part B on Feb 10 → Part B starts Mar 1.
Submit an MA/PDP application on Mar 5 → plan starts Apr 1.

Penalty note:
Signing up during GEP can mean Part B (and/or Part A) late enrollment penalties if you didn’t have creditable coverage.

How to Enroll in Medicare Part B

Automatic Enrollment in Medicare Part B

If you’re already receiving Social Security or Railroad Retirement Board (RRB) benefits when you turn 65, you’ll usually be automatically enrolled in both Part A and Part B.
Your Medicare card typically arrives 3 months before your 65th birthday.

Manual Enrollment in Medicare Part B

If you’re not receiving Social Security or RRB benefits, you must sign up through the Social Security Administration (SSA).

Important Note: If using an SEP after employer coverage, submit CMS-40B (Application for Part B) and CMS-L564 (Request for Employment Information)—your employer completes L564 to prove creditable, active coverage.

You can apply:

Online at SSA.gov
By phone at 1-800-772-1213
In person at a local Social Security office

When to Delay Enrolling into Medicare Part A

You may delay Part A if:

You’re still working.
Have employer coverage.
And want to keep contributing to an HSA.

In this case, you’ll enroll later during a Special Enrollment Period without penalty.

Employer Coverage Considerations:

If you or your spouse are still working and have employer coverage, Medicare and your employer plan coordinate payment.
If your employer has 20 or more employees: your employer plan is primary, and Part A is secondary.
If your employer has fewer than 20 employees: Medicare becomes primary, and the employer coverage is secondary.
If your employer coverage is creditable, you may delay Part A and/or B without penalty. However, many choose to enroll in free Part A for hospital coverage and keep their employer plan as primary.
Always check with your HR or benefits office to see how Medicare coordinates with your plan.

Health Savings Account (HSA) Impact:

If you’re contributing to an HSA, enrolling in Part A (even if premium-free) will stop your ability to keep making contributions.
Part A enrollment is often retroactive for up to 6 months, which can cause accidental tax penalties if you’ve contributed to your HSA during that time.

Medicare Part B Coverage

Medicare Part B Eligibility

Medicare Part B Premium Cost

When to Enroll in Medicare Part B

How to Enroll in Medicare Part B

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