Medicare Part B is the medical insurance piece that covers doctor visits, outpatient care, and preventive services

Medicare Part B pays for services from doctors, specialists, and outpatient facilities — the care you get when you're not admitted to a hospital overnight. It covers office visits, lab tests, imaging like X-rays and ultrasounds, mental health counseling, physical therapy, and most preventive screenings. Part B also covers durable medical equipment such as wheelchairs, walkers, and oxygen supplies when a doctor orders them.

Part B is optional, but most people who have Medicare Part A enroll in it. You pay a monthly premium for Part B, and you also pay a yearly deductible before Part B starts to pay its share. After you meet the deductible, you typically pay 20 percent of the cost for most services, and Medicare pays 80 percent.

Part B is different from Part A (hospital insurance) and Part D (prescription drug coverage). Together, these parts make up Original Medicare. Some people choose Medicare Advantage plans instead, which bundle Part A, Part B, and usually Part D into one plan run by a private insurance company.

Key Takeaways

  • Part B covers doctor visits, lab work, imaging, mental health services, and preventive care when you are not in a hospital.
  • You pay a monthly premium for Part B, a yearly deductible, and then 20 percent coinsurance for most services after the deductible is met.
  • Part B enrollment is optional but usually recommended; you can sign up during your initial enrollment period or during the General Enrollment Period each year.
  • If you delay Part B without a valid reason, you may face a permanent premium penalty when you do enroll.
  • Part B does not cover routine dental, vision, or hearing care, though some preventive screenings are included.

What Part B actually pays for

Part B covers visits to your primary care doctor, specialists, and urgent care clinics. It pays for lab tests ordered by your doctor, imaging such as CT scans and MRIs, and diagnostic procedures. If you need physical therapy, occupational therapy, or speech therapy, Part B covers those services when medically necessary and ordered by a doctor.

Preventive services covered by Part B include annual wellness visits, cancer screenings (mammograms, colonoscopies, Pap tests), cardiovascular screenings, diabetes screenings, bone density tests, and vaccinations such as flu shots and pneumonia vaccines. Mental health services, including therapy and psychiatric visits, are covered. Part B also pays for durable medical equipment — items like CPAP machines, hospital beds, and canes — when prescribed by a doctor.

Ambulance services are covered when medically necessary, as are certain outpatient surgeries and procedures performed in a hospital outpatient department or surgery center. Part B also covers some home health services, though these may also be covered under Part A depending on your situation.

What Part B does not cover

Part B does not pay for routine dental work, dentures, dental implants, or tooth extractions. Vision care such as routine eye exams, eyeglasses, and contact lenses are not covered, though Part B does cover certain eye conditions like glaucoma screening and treatment for age-related macular degeneration. Hearing aids and routine hearing exams are not covered by Part B.

Cosmetic surgery is not covered unless it is medically necessary to repair an injury or correct a deformity caused by illness or accident. Long-term care in a nursing home or assisted living facility is not covered by Part B. Routine foot care, such as nail trimming, is not covered unless you have diabetes or a condition affecting your feet.

Part B does not cover services from providers who are not enrolled in Medicare, though you may still receive care from them and pay out of pocket. Services that are not medically necessary, experimental treatments not approved by Medicare, and care from providers outside the United States are generally not covered.

How much Part B costs

The standard monthly premium for Part B changes each year. The amount you pay depends on your income — people with higher incomes pay a higher premium through an adjustment called Income-Related Monthly Adjustment Amount (IRMAA). If you receive Social Security, your Part B premium is usually deducted automatically from your benefit payment.

After you pay your monthly premium, you also pay an annual deductible before Part B coverage begins. Once you meet the deductible, you pay 20 percent coinsurance for most Part B services, and Medicare pays 80 percent. Some preventive services, such as annual wellness visits and certain screenings, are covered at no cost after you meet your deductible.

If you have a Medigap (supplemental insurance) plan, it may pay some or all of your deductible and coinsurance costs. If you have a Medicare Advantage plan, your costs work differently — you may have copays instead of coinsurance, and your deductible and out-of-pocket maximum may differ from Original Medicare.

When to enroll in Part B

You can enroll in Part B during your Initial Enrollment Period, which is the seven-month window that includes the month you turn 65, the three months before, and the three months after. If you enroll during this period, your coverage typically starts on the first day of the month you turn 65 or the first day of the following month, depending on when you enroll.

If you miss your Initial Enrollment Period, you can enroll during the General Enrollment Period, which runs from January 1 to March 31 each year. Coverage begins July 1 if you enroll during this window. However, if you enroll late without a valid reason, you will pay a permanent 10 percent premium penalty for as long as you have Part B.

You may be able to enroll in Part B outside these periods without penalty if you have a valid reason, such as employer coverage or certain life events. If you are still working and covered by your employer's health plan, you may be able to delay Part B enrollment without penalty.

Part B and other Medicare coverage

Original Medicare consists of Part A (hospital insurance), Part B (medical insurance), and optionally Part D (prescription drug coverage). You can use any provider who accepts Medicare, and you have flexibility in choosing doctors and specialists. However, Original Medicare does not include prescription drug coverage, so you need to enroll in Part D separately if you want that protection.

Medicare Advantage plans (Part C) are an alternative to Original Medicare. These plans are run by private insurance companies and must cover everything Part A and Part B cover, but they often include Part D as well. Medicare Advantage plans typically have lower premiums than Original Medicare plus a separate Part D plan, but they usually require you to use doctors and hospitals within their network.

Many people who choose Original Medicare also purchase a Medigap (supplemental insurance) plan to help pay for deductibles, coinsurance, and copays that Medicare does not cover. Medigap plans are sold by private insurance companies and are standardized, meaning the same plan letter (such as Plan G or Plan N) covers the same benefits regardless of which company sells it.

How to use Part B benefits

When you see a doctor or receive a service covered by Part B, show your Medicare card. The provider will bill Medicare directly if they are enrolled in Medicare. Medicare will pay its share (usually 80 percent after your deductible), and you will receive a bill for your share (usually 20 percent).

You can see any doctor or specialist who accepts Medicare — there is no need to choose a primary care doctor or get referrals, though some doctors may require one for their own office procedures. If you see a provider who does not accept Medicare assignment, you may pay more out of pocket, so it is worth asking before your visit.

Keep track of your deductible progress throughout the year. Once you have paid your annual deductible, your coinsurance rate stays at 20 percent for the rest of the calendar year. Your deductible resets on January 1 each year.

Frequently Asked Questions

Do I have to take Part B when I turn 65?

Part B is optional, but if you delay enrollment without a valid reason, you will pay a permanent 10 percent premium penalty. Most people enroll in Part B when they become may be able to access, but if you are still working and covered by your employer's health plan, you may be able to delay without penalty.

What happens if I see a doctor who does not accept Medicare?

You can still see the doctor and pay out of pocket, but Medicare will not pay its share. Some doctors accept Medicare but do not accept Medicare assignment, meaning they may charge you more than the Medicare-approved amount. Always ask whether a provider accepts Medicare and accepts assignment before your visit.

Does Part B cover prescription medications?

No. Part B does not cover prescription drugs. You need to enroll in Part D (prescription drug coverage) separately if you want that protection. Part D is offered by private insurance companies and covers most common medications.

Can I switch from Original Medicare to Medicare Advantage?

Yes. You can switch during the Annual Enrollment Period (October 15 to December 7 each year), and coverage changes on January 1. You can also switch back to Original Medicare during this period if you change your mind about a Medicare Advantage plan.

What is the difference between Part B coinsurance and a copay?

With Original Medicare Part B, you pay coinsurance, which is a percentage (usually 20 percent) of the Medicare-approved cost. With a Medicare Advantage plan, you typically pay a copay, which is a fixed dollar amount per visit. Coinsurance means your cost varies based on the service; a copay is the same amount every time.