Medicare Part B pays for doctor visits, outpatient care, and medical equipment — the services you use when you're not admitted to a hospital overnight

Medicare Part B is medical insurance that covers your doctor's office visits, lab tests, X-rays, ambulance rides, and durable medical equipment like wheelchairs or oxygen tanks. It also covers preventive care — annual wellness visits, cancer screenings, vaccinations — at no cost to you. Part B does not cover hospital stays (that's Part A), prescription drugs (that's Part D), or long-term care.

Part B is optional, but most people who have Part A should enroll in Part B. If you delay enrollment without a valid reason, you'll pay a permanent penalty on your premium for as long as you have Medicare. The monthly premium varies by income; in 2024 it ranges from about $175 to $560 per month for most people, though higher earners pay more.

You also pay a yearly deductible (currently $240) and then 20% coinsurance on most services after that. If you have a Medigap or Medicare Advantage plan, those costs may be lower or covered differently.

Key Takeaways

  • Part B covers doctor office visits, lab work, imaging, preventive screenings, and medical equipment — anything you need as an outpatient.
  • Part B is optional but carries a permanent premium penalty if you don't enroll when first may be able to access, unless you have employer coverage or another valid reason to delay.
  • You pay a monthly premium (income-based, roughly $175–$560), an annual deductible of $240, and then 20% of the cost of most services.
  • Part B works alongside Part A; together they form Original Medicare, which you can use at any hospital or doctor that accepts Medicare.

What Part B Actually Covers

Part B covers any medically necessary service a doctor orders as an outpatient. That includes office visits for any reason, blood tests and urinalysis, EKGs and stress tests, ultrasounds and CT scans, physical therapy and occupational therapy, mental health counseling, and dialysis. It also covers ambulance transport to a hospital, prosthetics, orthotics, wheelchairs, walkers, oxygen equipment, and diabetic supplies.

Preventive services are covered at 100% — you pay nothing. These include your annual wellness visit, colorectal cancer screening, mammography, bone density testing, cardiovascular screening, diabetes screening, depression screening, and most vaccinations including flu, pneumonia, and shingles shots. Part B also covers some preventive services you might not think of as medical: abdominal aortic aneurysm screening and carotid artery disease screening if you meet certain risk factors.

Part B does not cover routine dental, vision, or hearing care. It does not cover most prescription drugs (Part D handles that), and it does not cover long-term care in a nursing home or assisted living facility. It also does not cover cosmetic surgery or experimental treatments that Medicare determines are not medically necessary.

How Much Part B Costs

The monthly premium depends on your income. If your modified adjusted gross income from two years ago was below a certain threshold, you pay the standard premium. In 2024, that's roughly $175 per month. If your income was higher, you pay an Income-Related Monthly Adjustment Amount (IRMAA) on top of the standard premium, which can push your total to $560 or more per month.

After you pay your premium, you also pay an annual deductible of $240. Once you've met that deductible, you pay 20% coinsurance on most services — meaning Medicare pays 80% and you pay the remaining 20%. For some services like mental health visits, you may pay a flat copay instead of coinsurance.

If you have a Medigap plan (supplemental insurance), it typically covers your deductible and coinsurance, so your out-of-pocket costs are much lower. If you have a Medicare Advantage plan instead of Original Medicare, your costs work differently — you may have lower premiums but higher copays, and you're usually limited to in-network doctors.

When You Must Enroll in Part B

You become may be able to access for Medicare at 65. Your Initial Enrollment Period runs for seven months: three months before the month you turn 65, the month you turn 65, and three months after. If you enroll during this window, your coverage starts the month you turn 65 (or the first of the month after you turn 65, depending on your birthday).

If you miss your Initial Enrollment Period and you don't have a valid reason to delay — such as employer coverage through your job or your spouse's job — you'll pay a permanent penalty. The penalty is 10% of the standard premium for each full year you were may be able to access but not enrolled. That penalty stays with you for life, even after you finally enroll.

If you have employer coverage, you can delay Part B enrollment without penalty as long as you're still working and covered by that plan. Once you leave the job or lose the coverage, you have eight months to enroll in Part B without penalty. This is called a Special Enrollment Period.

Part B and Other Medicare Coverage

Part B is one piece of Original Medicare. Part A covers hospital stays, skilled nursing facility care, hospice, and some home health services. Together, Part A and Part B form the foundation of Original Medicare, and you can use them at any hospital, doctor's office, or facility that accepts Medicare.

You can add Part D (prescription drug coverage) to Original Medicare. Part D is sold by private insurance companies and covers most prescription medications. You should enroll in Part D when you first become may be able to access for Medicare, or within 63 days of losing other drug coverage, to avoid a permanent penalty.

Alternatively, instead of Original Medicare plus Part D, you can choose a Medicare Advantage plan (Part C). Medicare Advantage is an all-in-one plan sold by private insurers that includes Part A, Part B, and usually Part D coverage. You still pay your Part B premium to Medicare, but the Advantage plan handles the rest. The trade-off is that you're usually limited to in-network providers and may face higher copays.

How to Enroll in Part B

If you're already receiving Social Security benefits when you turn 65, Medicare will enroll you in Part A and Part B automatically. You'll receive your Medicare card in the mail about three months before your 65th birthday. If you don't want Part B, you must actively decline it in writing.

If you're not yet receiving Social Security, you need to enroll yourself. You can do this online at Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office. You'll need your Social Security number, proof of citizenship or legal residency, and information about any current health coverage.

If you miss your Initial Enrollment Period and you don't have a valid reason to delay, you can still enroll during the General Enrollment Period, which runs January 1 through March 31 each year. Coverage would start July 1 of that year. But remember: you'll owe the permanent penalty unless you had employer coverage or another may have access to reason to delay.

Common Mistakes to Avoid

The biggest mistake is not enrolling in Part B when you first become may be able to access. Many people think Medicare is optional or assume they can enroll anytime without penalty. The permanent 10% penalty applies for each year you delay without a valid reason, and it never goes away. If you delay for five years, you'll pay 50% more than the standard premium for the rest of your life.

Another common mistake is not understanding what Part B does and does not cover. Some people enroll in Part B but skip Part D, then are surprised that their prescriptions aren't covered. Others enroll in a Medicare Advantage plan thinking it's the same as Original Medicare, then discover their doctor isn't in the network. Read your plan documents carefully before your coverage starts.

A third mistake is not reviewing your coverage each year during Annual Enrollment Period (October 15 through December 7). Your health needs change, drug formularies change, and plan networks change. If your current plan no longer fits your needs, you can switch to a different plan or to Original Medicare during this window.

Frequently Asked Questions

Do I have to take Part B if I'm still working at 65?

No. If you or your spouse are still working and covered by an employer health plan, you can delay Part B without penalty. Once you leave the job or lose the coverage, you have eight months to enroll in Part B. After that window closes, you'll owe the permanent penalty if you enroll late.

What's the difference between Part B and a Medicare Advantage plan?

Part B is Original Medicare — you can see any doctor or hospital that accepts Medicare. A Medicare Advantage plan (Part C) is an alternative that includes Part B coverage but usually limits you to in-network providers and may have higher copays. You still pay your Part B premium either way.

Can I use Part B outside the United States?

Original Medicare Part B generally does not cover care outside the U.S., with rare exceptions for emergency care in Canada or Mexico near the border. If you travel internationally, you may want to purchase a travel insurance policy. Medicare Advantage plans also typically don't cover foreign care.

What happens if I can't afford the Part B premium?

If your income is very low, you may may have access to for Medicaid, which can help pay your Medicare premiums and cost-sharing. Contact your state Medicaid office or call 1-800-MEDICARE for a referral. Some nonprofit organizations also offer information with Medicare costs.

Does Part B cover my annual physical?

Yes. Part B covers an annual wellness visit at no cost to you (after you've met your deductible, though preventive visits are often covered at 100%). This is different from a traditional physical — it's a preventive visit focused on screening and planning. If your doctor does additional diagnostic work during the visit, you may owe coinsurance on those services.