What Is Medicare Part B? Coverage, Costs & Enrollment Guide

What is Part B of Medicare? Part B is the medical insurance part of the Medicare which covers doctor visits, outpatient care, preventive care as well as durable medical equipment.In 2026 the standard monthly premium will be $185.00 with a deductible of $257 per annum.Once you have paid the deductible, you have a coinsurance amount of 20% which applies to most services and there is no out-of-pocket maximum. Most beneficiaries pair Part B with a Medigap supplement or Medicare Advantage plan to cap that 20% exposure.

This guide walks through what Part B covers, what it costs in 2026, how to enroll, and the late penalty trap that costs new beneficiaries thousands of dollars each year. Information comes from Medicare.gov, CMS, and KFF.

What does Medicare Part B cover?

Part B medicare coverage focuses on outpatient and physician services. Anything that happens at a doctor's office, an outpatient clinic, or as a preventive screening typically falls under Part B.

What does Medicare Part B cover specifically:

• Doctor visits including specialists, second opinions, and consultations

• Outpatient hospital services like same-day surgery and emergency room visits where you're not admitted

• Preventive services including annual wellness visits, vaccines, and cancer screenings

• Mental health services including outpatient therapy and psychiatric visits

• Durable medical equipment like wheelchairs, walkers, oxygen, and diabetic supplies

• Lab tests and X-rays ordered by your provider

• Ambulance services when medically necessary

• Limited prescription drugs that must be administered by a provider (chemotherapy, certain injections)

What Part B does not cover: most dental work, routine vision and hearing care, hearing aids, long-term care, and most prescriptions taken at home (those fall under Part D). For dental gaps, see our does Medicare cover dental guide.

Medicare Part B cost in 2026

The Medicare Part B premium in 2026 is $185.00 per month for most beneficiaries, according to CMS's 2026 cost announcement. This is up from $174.70 in 2025. Higher-income beneficiaries pay more under the Income-Related Monthly Adjustment Amount (IRMAA), which kicks in at modified adjusted gross income above $106,000 for individuals or $212,000 for couples filing jointly.

For couples filing jointly, the income brackets double. Your IRMAA is based on your tax return from two years ago. If your income has dropped significantly since then (retirement, divorce, death of a spouse), you can request a reconsideration through SSA.

Medicare Part B deductible 2026

The Medicare Part B deductible 2026 is $257, up from $240 in 2025.After paying the deductible, you have to pay a coinsurance of 20% on most Part B services.The remaining 80% is covered by Medicare.No separate annual out-of-pocket maximum of Original Medicare Part B.To learn more about the deductible, refer to our Part B deductible 2026 guide.

The largest break in Original Medicare is the 20 percent coinsurance. One outpatient surgery in a hospital at a cost of $40,000 leaves you holding on to the cost of 8,000.That is why the majority of the beneficiaries combine Part B with a Medigap plan such as Plan G or Plan N that covers that 20%.

Medicare Part B enrollment

Part B enrollment depends on whether you're getting Social Security benefits and whether you have other coverage.

If you're already receiving Social Security at 65: You're enrolled in Parts A and B automatically. Your Medicare card arrives in the mail about three months before your 65th birthday.

If you're not receiving Social Security yet: You need to actively enroll during your Initial Enrollment Period (IEP), which is the 7-month window starting 3 months before your 65th birthday and ending 3 months after.

If you have employer coverage from a company with 20+ employees: You can delay Part B enrollment without penalty as long as you maintain creditable coverage. When that coverage ends, you have an 8-month Special Enrollment Period to sign up.

If you have employer coverage from a company with fewer than 20 employees: Medicare becomes your primary insurance at 65, even if you're still working. You should enroll in Part B during your Initial Enrollment Period to avoid coverage gaps.

You enroll through the Social Security Administration online at SSA.gov, by phone, or in person. Your State Health Insurance Assistance Program (SHIP) offers free enrollment counseling.

The Part B late enrollment penalty

This is the pit that most individuals are unaware of.Failure to enroll in Part B at the first opportunity and not having any other qualifying coverage would result in a permanent payment penalty of 10% on each full 12-month period you lacked coverage.

The punishment will be until the end of your life on Medicare.Example: When you defer Part B by 3 years and do not have a qualifying coverage, permanently increase your premium by 30%.With the standard premium of $185.00 in 2026, that would be approximately 55 more each month or 660 more per year, every year you have Medicare.

More than 20 years of retirement that amounts to over 13,000 penalty payments.The remedy is easy: enroll during your Initial Enrollment Period, or be sure to have qualifying coverage (employer plan, COBRA does not count) before delaying.

Original Medicare vs Medicare Advantage for Part B

Once you enroll in Part B, you choose how to receive your benefits. Two paths:

Original Medicare uses Parts A + B with the federal government as your insurer. You can add Part D for prescriptions and Medigap to fill the 20% coinsurance gap. You can see any provider that accepts Medicare, no networks.

Medicare Advantage (Part C) replaces Original Medicare with a private insurer's plan that bundles A, B, and usually D. Networks apply, prior authorization is common, but premiums are often lower and many plans include dental, vision, and hearing.

About 54% of Medicare-eligible adults choose Medicare Advantage in 2026, per KFF. The other 46% stay with Original Medicare, usually with a Medigap supplement.