What Is Medicare Part B? Medical Insurance

What Is Medicare Part B?

Direct answer: Medicare Part B is medical insurance covering outpatient and preventive care — everything from doctor visits and diagnostic tests to durable medical equipment and mental health services. It focuses on two categories: medically necessary services needed to diagnose or treat a condition, and preventive services designed to catch problems early or prevent them entirely. Understanding what’s actually included, and what genuinely isn’t, is what lets you plan realistically for the coverage gaps you’ll need to fill separately.

What Does Medicare Part B Cover?

• Doctor visits and specialists
• Outpatient care — treatments or procedures that don’t require hospital admission, including clinic-based services
• Diagnostic tests and lab work — blood tests, screenings, X-rays, and imaging
• Preventive care — flu shots, cancer screenings, diabetes testing, and an annual wellness visit
• Durable medical equipment — wheelchairs, walkers, blood sugar monitors, and similar doctor-prescribed items
• Mental health services — counseling and therapy, covered more broadly today than in the past (more below)
• Rehabilitation services — physical and occupational therapy
• Ambulatory surgical center services
• Speech-language pathology
• Some home healthcare services

Has Mental Health Coverage Under Part B Changed Recently?

Yes, meaningfully — this is worth knowing if you’re working from older information about what kind of therapist Medicare will actually cover. Medicare recently expanded which mental health providers can bill Part B directly, adding licensed marriage and family therapists and licensed mental health counselors to the list of providers Medicare recognizes — over 400,000 newly eligible providers nationwide, and the first expansion of covered mental health provider types in decades. Previously, only psychiatrists, other physicians, clinical psychologists, and clinical social workers could bill Medicare directly for these services.

One practical caveat if you’re on Medicare Advantage rather than Original Medicare: not every Medicare Advantage plan automatically includes these newly-eligible provider types in its network. If you’re specifically looking to see a marriage and family therapist or licensed mental health counselor, confirm your plan actually covers that provider type before scheduling, rather than assuming coverage follows automatically from the broader Part B rule.

Under Original Medicare, there’s no restriction on the frequency or number of counseling sessions covered, and coverage extends across various therapy approaches, as long as your provider is licensed and accepts Medicare.

What Doesn’t Medicare Part B Cover?

• Most prescription drugs — requiring a separate Part D plan or Medicare Advantage plan with drug coverage.
• Vision care, including routine exams and glasses, routine dental care and dentures, and hearing aids and related exams — all excluded except in narrow, specific medical circumstances. For the full picture of these exceptions, see our guides on Medicare and vision coverage and Medicare and dental coverage.
• Cosmetic surgery, unless medically necessary.
• Long-term custodial care — a separate, often much larger financial risk requiring its own planning.

If you need coverage for these excluded categories, Medicare Advantage or standalone supplemental insurance are the typical paths to fill the gap.

What Does Medicare Part B Cost?

Premiums and deductibles: Part B carries a standard monthly premium set by the government, with higher earners paying an additional income-related surcharge (IRMAA) — which can be appealed if your income has genuinely dropped due to a specific qualifying event. You’ll also meet an annual deductible before Part B coverage kicks in.

Coinsurance: Once your deductible is met, you’re typically responsible for roughly 20% of the Medicare-approved amount for most services, with Medicare covering the remaining 80%.

Out-of-pocket costs for excluded services: Anything Part B doesn’t cover — routine vision or dental care, for example — needs to be paid out of pocket unless you have supplemental coverage that addresses it specifically.

When Do I Enroll in Medicare Part B?

Your Initial Enrollment Period is a seven-month window — three months before your 65th birthday month, your birthday month, and three months after. Missing this window without qualifying for a Special Enrollment Period can mean a permanent late enrollment penalty.

If you’re already receiving Social Security benefits, you’re automatically enrolled. Otherwise, you’ll need to actively sign up through the Social Security Administration.

Bottom Line

Medicare Part B forms the backbone of your outpatient medical coverage, and its scope is broader than many people assume — particularly with the recent expansion of covered mental health providers, which meaningfully widens practical access to therapy. But real gaps remain: vision, dental, hearing, and prescription drugs all require separate coverage, and understanding exactly where those boundaries sit is what lets you plan around them deliberately rather than discovering them during a medical visit. An independent Medicare broker can help you explore Medigap or Medicare Advantage options to fill these gaps based on your specific needs.

Key Takeaways

• Medicare Part B covers outpatient medically necessary and preventive care, including doctor visits, diagnostic tests, durable medical equipment, and mental health services.
• Medicare recently expanded covered mental health providers to include licensed marriage and family therapists and licensed mental health counselors — the first expansion of provider types in decades.
• Medicare Advantage enrollees should confirm their specific plan’s network includes these newly-eligible provider types, since coverage isn’t automatic across every plan.
• Part B excludes most prescription drugs, routine vision and dental care, hearing aids, cosmetic surgery, and long-term custodial care.
• Standard Part B cost-sharing includes a monthly premium (higher for high earners via IRMAA), an annual deductible, and roughly 20% coinsurance on most services.
• Your Initial Enrollment Period is a seven-month window centered on your 65th birthday — missing it without a qualifying reason to delay risks a permanent penalty.

FAQ

What does Medicare Part B cover?
Outpatient medical care — doctor visits, diagnostic tests, preventive services, durable medical equipment, mental health services, and outpatient rehabilitation.

Does Medicare Part B cover therapy or counseling?
Yes, and coverage recently expanded to include licensed marriage and family therapists and licensed mental health counselors, in addition to psychiatrists, psychologists, and clinical social workers.

Do all Medicare Advantage plans cover the newly-eligible mental health providers?
Not automatically — confirm your specific plan’s network includes marriage and family therapists or mental health counselors before scheduling if that’s the provider type you need.

What doesn’t Medicare Part B cover?
Most prescription drugs, routine vision and dental care, hearing aids, cosmetic surgery, and long-term custodial care.

How much does Medicare Part B cost?
A monthly premium (higher for high earners), an annual deductible, and roughly 20% coinsurance on most covered services after the deductible is met.

When do I need to enroll in Medicare Part B?
During your seven-month Initial Enrollment Period centered on your 65th birthday, unless you qualify for a Special Enrollment Period due to active employer coverage.