Medicare Part B

Medicare Part B can feel like “the confusing half” of Medicare, because it touches so many everyday health care situations. The good news is the big picture is simple: Part B is the part of Original Medicare that helps cover most doctor-and-outpatient care, along with many preventive services.

This guide walks you through what Part B is, what it covers, how enrollment works, and how costs like deductibles, copays, and coinsurance usually show up.

What is Medicare Part B?

Medicare Part B is often described as Medicare’s medical insurance. In plain English, it’s the part that helps pay for many of the services you use when you’re not admitted as a hospital inpatient—things like doctor visits, outpatient tests, and preventive care. Part B is part of Original Medicare (Part A + Part B).

Think of it this way:

Part A is more about inpatient hospital coverage.
Part B is more about doctor services, outpatient care, and preventive services you use throughout the year.

That “throughout the year” part matters. For many people, Part B is what they use most often.

A female doctor examines an elderly man's back using a stethoscope.

What does Medicare Part B cover?

Part B covers a wide range of services, but the easiest way to understand it is in “buckets.” Here are the most common ones you’ll see.

Services from doctors and other health care providers

Part B generally helps cover:

Office visits and consultations
Specialist visits
Many medically necessary services you get from a provider (in or out of a hospital setting)

Outpatient care

Part B commonly covers:

Hospital outpatient services
Emergency department care (as an outpatient)
Outpatient procedures and surgeries (when performed in an outpatient setting)

Part B doesn’t cover “everything medical.” Coverage usually depends on medical necessity, the type of service, and the setting where you receive care

Tests and diagnostics

Part B often helps pay for medically necessary:

Lab tests
Imaging and diagnostic tests (like X-rays and other ordered testing)

Durable medical equipment

Part B commonly covers durable medical equipment (DME) when it’s medically necessary and prescribed, such as:

Walkers
Wheelchairs
Hospital beds
Oxygen equipment (when you meet Medicare’s rules)

Many preventive services

Part B includes many preventive services that are designed to catch issues early, such as:

Screenings (when you meet eligibility rules)
Shots or vaccines (certain preventive vaccines)
“Wellness” style preventive visits

Other common covered categories

Part B also lists coverage for items such as:

Ambulance services (when medically necessary)
Mental health and substance use disorder services
Limited outpatient prescription drugs (more on that in a moment)

A father and his son share a laugh during a chess game.

How do I qualify for Medicare Part B?

Most people qualify for Medicare when they turn 65, or earlier in certain disability-related situations. Part B is part of Medicare, but enrollment rules can vary depending on your situation—especially if you have coverage through current work.

A helpful way to think about “qualify” vs “enroll” is:

Qualify: You’re eligible for Medicare.
Enroll: You sign up for Part B (and choose when it begins, based on your enrollment period rules)

When can I enroll in Medicare Part B?

Timing matters with Part B. If you enroll at the right time, you can often avoid gaps and potential penalties. Medicare describes a few main enrollment paths.

Initial Enrollment Period (IEP)

This is your first main opportunity to sign up around age 65. It’s a multi-month window that includes the months before, during, and after your 65th birthday month.

Special Enrollment Period (SEP)

If you (or your spouse) have qualifying coverage from current work, you may be able to enroll in Part B later, without the usual penalty—but the timing and rules are specific, so it’s worth confirming your situation.

General Enrollment Period (GEP)

If you missed your Initial Enrollment Period and don’t qualify for a Special Enrollment Period, Medicare has a General Enrollment Period each year. Medicare explains that when you enroll during this window, coverage starts after you sign up, and you may owe a late enrollment penalty if you didn’t have a qualifying Special Enrollment Period

What is the Part B monthly premium?

Most people pay a monthly premium for Part B, and that premium can change from year to year.

Income-related adjustments (IRMAA)

Some people pay more for Part B based on income. This is commonly called an income-related monthly adjustment amount (IRMAA). In simple terms: higher income can mean a higher Part B premium.

How you pay it

Many people have the Part B premium deducted from Social Security (or related benefits). Others may be billed directly, depending on how they receive benefits and how they enrolled

How Part B cost-sharing works

Part B costs aren’t just the monthly premium. It also helps to understand the three words you’ll see everywhere:

Deductible: What you may pay before Medicare starts paying its share for many Part B-covered services.
Copay: A set amount you may pay for certain services (this can depend on the setting, and can show up more often in plan-based coverage).
Coinsurance: A percentage of the Medicare-approved amount you may pay after the deductible.

Here’s the “typical shape” many people experience:

You pay the Part B premium each month.
You may need to meet a deductible.
After that, many services involve coinsurance (and sometimes copays, depending on the situation).

One more detail that can affect your costs

Whether your provider accepts Medicare and follows Medicare’s billing rules can affect what you pay out of pocket. If you’re trying to avoid surprises, it’s reasonable to ask a provider’s office how they bill Medicare before a test, procedure, or equipment order.

An orange sunrise illuminates a sunflower field.

How can I get help to pay for Medicare?

If costs are tight, you’re not alone—and there are programs designed to help.

Medicare Savings Programs

Medicare Savings Programs (MSPs) are state-run programs that can help people with limited income and resources pay Medicare costs. If you qualify, an MSP may help pay your Part A and/or Part B premiums, and it may also help with deductibles, coinsurance, and copays.

Medicare’s guidance is simple here: even if you’re not sure you qualify, it’s still worth applying.

Medicare Part B summary

Medicare Part B is the part of Original Medicare that helps cover many of the services you use most often—doctor visits, outpatient care, diagnostic testing, durable medical equipment, and many preventive services.

Enrollment timing matters (Initial, Special, and General Enrollment Periods), and missing the right window can lead to delayed coverage and possible penalties.

Finally, Part B costs usually include a monthly premium, plus cost-sharing like deductibles, copays, and coinsurance. If paying for Medicare is difficult, Medicare Savings Programs may help with premiums and other out-of-pocket costs if you qualify.

References

Medicare.gov — Parts of Medicare (Part B overview). https://www.medicare.gov/basics/get-started-with-medicare/medicare-basics/parts-of-medicare ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸
Medicare.gov — What Part B covers. https://www.medicare.gov/providers-services/original-medicare/part-b ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸
Medicare.gov — When does Medicare coverage start? (IEP, SEP, GEP basics). https://www.medicare.gov/basics/get-started-with-medicare/sign-up/when-does-medicare-coverage-start ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷
Social Security Administration — When to sign up for Medicare (enrollment timing overview). https://www.ssa.gov/medicare/plan/when-to-sign-up ↩ ↩² ↩³
CMS — 2026 Medicare Parts A & B Premiums and Deductibles (annual updates). https://www.cms.gov/newsroom/fact-sheets/2026-medicare-parts-b-premiums-deductibles ↩
Medicare.gov — Medicare Costs (PDF overview, including premium and income-related concepts). https://www.medicare.gov/publications/11579-medicare-costs.pdf ↩ ↩² ↩³
Medicare.gov — Medicare costs (Part B cost-sharing concepts). https://www.medicare.gov/basics/costs/medicare-costs ↩ ↩² ↩³ ↩⁴ ↩⁵
Medicare.gov — Medicare Savings Programs. https://www.medicare.gov/basics/costs/help/medicare-savings-programs ↩ ↩² ↩³ ↩⁴
Colorado HCPF — Medicare Savings Programs (Colorado). https://hcpf.colorado.gov/medicare-savings-programs-msp

This website is for educational purposes only. It isn’t medical advice, legal advice, or financial advice. It also isn’t a promise of coverage or payment. For official Medicare information, visit Medicare.gov. You can also get free, unbiased help from your State Health Insurance Assistance Program (SHIP). For personal medical guidance, talk with your doctor, and review your Medicare plan documents.