What Is Medicare Part B? Coverage, Costs, and Enrollment Explained

Medicare Part B is one of two parts that make up what most people call “Original Medicare.” If you’re approaching 65, already enrolled, or helping a parent navigate health coverage, understanding Part B is essential — it covers the medical services you’re most likely to use.

Part B is the everyday layer of Medicare: doctor visits, outpatient care, medical equipment, and a long list of preventive services — many at no cost to you — for a standard premium of $202.90 a month in 2026. Its boundaries matter as much as its benefits: routine dental, vision, and hearing aids are excluded, and enrolling late without qualifying coverage adds a permanent 10% surcharge for every full year you delayed.

What Is Medicare Part B?

Medicare Part B is the medical insurance component of Original Medicare. It covers outpatient services — everything that doesn’t require you to be admitted to a hospital. The other component, Medicare Part A, covers inpatient hospital stays, skilled nursing facility care, and hospice.

Together, Parts A and B form the foundation of Medicare coverage. Most people get both parts simultaneously, though you can have one without the other in certain situations.

Part B is administered by the federal government through the Centers for Medicare & Medicaid Services (CMS). Coverage is standardized — Part B covers the same services for everyone enrolled, regardless of where you live.

What Does Medicare Part B Cover?

Medicare Part B covers two main categories of services:

Medically Necessary Services

“Medically necessary” means services or supplies that are needed to diagnose or treat your medical condition and meet accepted standards of medical practice. Part B covers:

• Doctor visits — office visits with your primary care physician, specialists, surgeons, and other licensed practitioners
• Outpatient hospital care — emergency department visits, observation stays, and same-day surgeries where you aren’t formally admitted
• Ambulance services — emergency transportation when other transport would endanger your health
• Durable medical equipment (DME) — wheelchairs, walkers, oxygen equipment, and blood sugar monitors prescribed by a doctor
• Mental health services — outpatient therapy, psychiatric evaluation, and substance use disorder treatment
• Dialysis — kidney dialysis treatment at a facility or at home
• Second surgical opinions — Part B encourages getting a second opinion before elective surgery
• Lab tests and X-rays — when ordered by your doctor as part of diagnosing or treating a condition
• Outpatient physical, occupational, and speech therapy — to help restore function after injury or illness

Preventive Services

One of the most valuable aspects of Part B is its coverage of preventive care — often at no cost to you. Preventive services covered include:

• Annual Wellness Visit — a yearly check-in with your doctor to review your health and create a personalized prevention plan
• Cardiovascular screenings — cholesterol, lipid, and triglyceride tests
• Cancer screenings — mammograms, Pap smears, colorectal cancer screenings, prostate cancer screenings, and lung cancer screenings (for qualifying smokers)
• Bone density measurements — to screen for osteoporosis
• Depression screening — once per year in a primary care setting
• Diabetes screening — for people at risk
• Flu shots, Pneumococcal vaccines, and Hepatitis B vaccines
• Obesity screening and counseling
• Tobacco cessation counseling — up to 8 sessions per year

Most preventive services are covered at 100% (no cost to you) when provided by a Medicare-participating provider.

What Part B Does NOT Cover

Understanding the limits of Part B is equally important. Part B does not cover:

• Prescription drugs — these are covered under Medicare Part D, a separate plan
• Dental care — routine dental exams, fillings, dentures, and extractions are generally not covered
• Vision care — routine eye exams and glasses are not covered (though cataract surgery is)
• Hearing aids — hearing exams and hearing aids are not covered (though surgically implanted cochlear implants are, as prosthetic devices)
• Long-term custodial care — help with daily activities like bathing and dressing in a nursing home or at home
• Cosmetic surgery — unless required after an accidental injury or to repair a defect

These coverage gaps are why many people purchase a Medicare Supplement (Medigap) plan or choose Medicare Advantage instead of Original Medicare.

How Much Does Medicare Part B Cost in 2026?

Medicare Part B has several cost components:

Monthly Premium

The standard Part B monthly premium for 2026 is $202.90 per month. Most people pay this amount directly from their Social Security benefit.

However, higher-income beneficiaries pay more. The Income-Related Monthly Adjustment Amount (IRMAA) adds a surcharge for individuals whose modified adjusted gross income (MAGI) exceeds certain thresholds.

IRMAA is based on your income from two years prior — your 2024 tax return determines your 2026 premium. If your income has since dropped because of a qualifying life event (retirement, the death of a spouse, divorce, or loss of an income-producing property), you can appeal the surcharge using Form SSA-44. See our full guide to IRMAA surcharges and the income brackets and the life-changing events that let you appeal.

How the premium is paid. If you already collect Social Security, your Part B premium is deducted automatically from your monthly benefit before it reaches your bank account. If you’ve delayed Social Security, Medicare bills you directly (quarterly by default, or monthly through Medicare Easy Pay). A federal “hold harmless” provision protects most enrollees whose premium is deducted from Social Security: in years when the Part B premium rises faster than the Social Security cost-of-living adjustment, your premium increase can’t exceed your dollar COLA increase — so your net Social Security check never goes down. The hold-harmless rule does not apply to new enrollees, to people who pay IRMAA, or to those billed directly.

If the premium is a hardship. Beneficiaries with limited income and assets can have the entire Part B premium paid for them through a Medicare Savings Program — the Qualified Medicare Beneficiary (QMB) program alone restores roughly $2,435 per year straight back into the Social Security deposit. Many people who qualify never apply because they assume their income is too high. Read how Medicare Savings Programs work to check the 2026 limits.

Annual Deductible

Before Medicare pays for most services, you must first meet the Part B deductible. In 2026, the deductible is $283 per year.

Coinsurance

After meeting your deductible, Medicare Part B pays 80% of approved charges for most services. You pay the remaining 20% — and there is no out-of-pocket maximum in Original Medicare alone.

This 20% coinsurance is one of the primary reasons people buy Medigap coverage. A major surgery or extended outpatient treatment can result in substantial bills if you have no supplemental coverage.

A Worked Example: What Part B Actually Pays

Suppose you have an outpatient procedure with a Medicare-approved amount of $10,000 and it’s your first Part B service of the year:

1. You pay the $283 deductible first.
2. On the remaining $9,717, Medicare pays 80% ($7,773.60) and you pay the 20% coinsurance ($1,943.40).
3. Your total out-of-pocket is $2,226.40 — and because Original Medicare has no out-of-pocket maximum, a second major event later that year starts the 20% meter running all over again.

This is the single most important number on the page. The premium is predictable; the open-ended 20% is the real financial exposure, and it’s why most people pair Part B with either a Medigap policy or a Medicare Advantage plan. For the bigger retirement picture, see our breakdown of healthcare costs in retirement.

Assignment and “Excess Charges”

The 80/20 math above assumes your provider accepts Medicare assignment — meaning they agree to accept the Medicare-approved amount as full payment. The vast majority of doctors do.

A provider who is enrolled in Medicare but does not accept assignment (“non-participating”) can legally bill you up to 15% more than the approved amount. This surcharge is called a Part B excess charge, and it’s on top of your normal 20% coinsurance. On a $10,000 service that’s an extra $1,500 out of your pocket.

Two things protect you: most states and most providers don’t allow excess charges in practice, and Medigap Plan G and Plan F specifically cover Part B excess charges in full. Before any non-emergency procedure, it’s worth asking the simple question, “Do you accept Medicare assignment?”

Part B Also Covers Some Drugs

A common point of confusion: while Medicare Part D covers the prescriptions you fill at a pharmacy, Part B covers drugs that are administered in a clinical setting — chemotherapy infusions, injectable biologics given in a doctor’s office, and most vaccines. These are billed under the same 20% coinsurance rule, which means an expensive office-administered drug can carry an uncapped 20% bill. Understanding the Part B vs. Part D drug split is one of the most valuable cost distinctions in all of Medicare.

When to Enroll in Medicare Part B

Enrollment timing matters enormously. Miss the right window and you’ll pay a permanent premium penalty.

Initial Enrollment Period (IEP)

Your first chance to enroll in Part B is the 7-month Initial Enrollment Period surrounding your 65th birthday:

• 3 months before the month you turn 65
• The month you turn 65
• 3 months after the month you turn 65

Enrolling during the first 3 months of your IEP means your coverage starts the month you turn 65. Enrolling in month 4 or later delays your start date by one to three months.

Special Enrollment Period (SEP)

If you’re still working at 65 and covered by an employer group health plan (through your own job or a spouse’s), you can delay Part B enrollment without penalty. You’ll have a Special Enrollment Period — 8 months after your employment or group coverage ends — to sign up.

Important: COBRA and retiree health coverage do not count as active employment coverage for this purpose. Relying on COBRA to delay Part B enrollment will trigger the late penalty.

General Enrollment Period

If you miss both the IEP and any applicable SEP, you can enroll during the General Enrollment Period: January 1 through March 31 each year, with coverage starting July 1.

Late Enrollment Penalty

If you don’t have qualifying coverage and delay Part B enrollment beyond your IEP, you’ll pay a 10% premium surcharge for each full 12-month period you were eligible but not enrolled. This penalty is permanent — it doesn’t go away after a few years.

For example, delaying enrollment by two years adds 20% to your monthly premium for life. At the 2026 standard premium of $202.90/month, that’s an extra $40.58/month — about $487 a year, forever. And because the penalty is a percentage, it recalculates against the standard premium every year, so it grows as the base premium rises. Delay long enough and the lifetime cost runs well into five figures.

The penalty trips up people who assume any health coverage lets them postpone Part B. It doesn’t — only active employer group coverage through your own or a spouse’s current job qualifies. To see exactly which windows apply to your situation, read our guide to Medicare enrollment periods, and if you’re still on the job at 65, working past 65 and Medicare and Medicare vs. employer insurance at 65.

A Trap for HSA Savers

If you contribute to a Health Savings Account, there’s a timing wrinkle worth knowing: you cannot contribute to an HSA once you’re enrolled in any part of Medicare, and Part A (if you take it) backdates up to six months. Many people who keep working past 65 deliberately delay both Part A and Part B to preserve HSA eligibility — see HSAs and Medicare before you enroll.

How Part B Works With Other Coverage

With Part A: Together, Parts A and B cover a wide range of medical needs, but leave gaps — the 20% coinsurance, the deductible, and excluded services. Most people fill these gaps with either a Medigap plan or a Medicare Advantage plan.

With Medicare Advantage (Part C): If you choose Medicare Advantage, your Part A and B coverage is bundled into a private insurance plan. You still pay the Part B premium, but the Advantage plan takes over coordination of your benefits.

With Medigap: If you keep Original Medicare (Parts A and B), a Medigap plan covers much of what Part B doesn’t — often including the 20% coinsurance, the deductible, and sometimes coverage during foreign travel.

With employer coverage: If you have retiree health coverage from a former employer, it typically works alongside Medicare rather than replacing it. The coordination of benefits rules determine which pays first.

Two Lesser-Known Part B Benefits

Mental health, expanded. As of recent rule changes, Part B now pays for services from licensed marriage and family therapists and mental health counselors — not just psychiatrists, psychologists, and clinical social workers — and covers intensive outpatient programs. If behavioral health is a concern, see Medicare’s mental health coverage.

The immunosuppressive drug benefit (Part B-ID). Kidney transplant recipients whose Medicare would otherwise end 36 months after a successful transplant can now keep a limited Part B benefit that covers only immunosuppressive drugs, for a reduced premium. It’s narrow, but for transplant patients it prevents a catastrophic coverage cliff.

Frequently Asked Questions

Is Medicare Part B mandatory? No — Part B is optional. But if you don’t have qualifying active-employer coverage and you delay, you’ll owe the permanent late-enrollment penalty when you finally sign up. For most people without employer coverage, enrolling at 65 is the right call.

Can I have Part B without Part A? Yes, though it’s uncommon. Nearly everyone gets premium-free Part A automatically, so most people take both. You can also take Part A without Part B if you’re still covered by employer insurance.

Does Part B cover dental, vision, or hearing? Generally no. Routine dental, vision, and hearing care are excluded (cataract surgery and some medically necessary services are exceptions). Many people choose a Medicare Advantage plan partly to get these extras bundled in.

How do I lower my Part B costs? Three main levers: a Medigap policy to cover the 20% coinsurance, a Medicare Savings Program if your income is limited, and careful income planning to stay under the IRMAA thresholds.

When should I claim Social Security relative to enrolling in Part B? They’re separate decisions. You can enroll in Part B at 65 while delaying Social Security to grow your benefit — Medicare will simply bill you directly until your Social Security starts. See when to claim Social Security for the trade-offs.

Key Takeaways

• Medicare Part B covers outpatient medical care, doctor visits, preventive services, and durable medical equipment
• The standard 2026 premium is $202.90/month; higher earners pay more via IRMAA
• After the $283 annual deductible, Part B pays 80% — you pay 20% with no cap
• Enroll during your Initial Enrollment Period (the 7 months around your 65th birthday) or face a permanent late penalty
• Delaying is penalty-free only if you’re covered by an active employer group health plan through your own or a spouse’s current job

Understanding Part B is the foundation for every other Medicare decision you’ll make. Next, explore how Medicare Advantage compares to Original Medicare to decide which path makes more sense for your situation.

Sources

• Medicare.gov — Medicare costs
• CMS.gov — 2026 Medicare Parts A & B premiums and deductibles (fact sheet)
• Medicare.gov — Get started with Medicare
• Medicare.gov — Preventive and screening services

All sources are official government or nonprofit consumer resources, verified July 2026. Medicare and Social Security rules and dollar amounts change annually — confirm current figures at the links above before making decisions.