What does Medicare Part B cover?

You have a test. Medicare covers it either way, but where you have it changes what you pay, and Medicare says so in its own words. The same service in a hospital outpatient department may cost you more than it would in a doctor's office.

What does Medicare Part B cover?

Medicare Part B covers many diagnostic and treatment services you get as an outpatient from a hospital that takes Medicare. Its reach is wider than that. Medicare's own costs page prices six separate service categories under Part B, and that price list is the clearest map of the scope.

Start with the sentence itself, because it carries two conditions rather than one. The care has to be delivered to you as an outpatient, and the hospital has to be one that takes Medicare.

The costs page then names what it is pricing. Clinical laboratory services. Home health care, and durable medical equipment inside the same row. Doctor services while you are a hospital inpatient. Outpatient mental health care. Partial hospitalization mental health care. Outpatient hospital care.

Two of those deserve a second look for opposite reasons. Part B reaches inside a hospital admission, paying for most doctor services while you are an inpatient, so it is not only the part for care outside a hospital. And mental health appears twice, on two separate rows, which is its own subject in the Coverage section rather than this page's.

Above the categories sits the rule that governs most of them. You usually pay 20 percent of the cost for each Medicare-covered service or item after you have paid your deductible, as long as your doctor or health care provider accepts the Medicare-approved amount as full payment. Medicare calls that last part accepting assignment.

One row breaks the pattern completely, and it is the row this page returns to at the end.

What does it not cover?

Medicare does not publish a single consumer page listing what Part B leaves out. The exclusion this page can state from its own sources is drugs: Part B generally does not cover prescription and over-the-counter drugs you get in an outpatient setting, though the rule has a covered exception inside it.

Take the absence first. Looking for a single page on Medicare.gov that answers what Medicare does not cover, this publication found none on August 12, 2026. The coverage answers sit on one page per service instead. That is our finding, not Medicare's statement, and it is the reason this section is narrow rather than long.

Now the exclusion, in the order Medicare writes it, because the order is part of the answer. Medicare's list of covered outpatient hospital services includes certain self-administered drugs and biologicals you get as part of your service or procedure, like certain injectable drugs.

Then, in the same item, the general rule. Part B does not cover prescription and over-the-counter drugs you get in an outpatient setting, the ones Medicare calls self-administered drugs.

So the exclusion is filed inside the covered list, with a covered category standing in front of it. Read only the second half and Part B looks like it never pays for a drug in an outpatient setting. Read the whole item and the boundary sits between a drug given as part of your procedure and a drug you would otherwise take yourself.

Medicare adds a practical note next to it: for safety reasons, many hospitals have policies that do not allow patients to bring prescription or other drugs from home.

Dental, vision and hearing are three separate questions with three separate answers. Neither of this page's two sources answers any of them, so this page names the three and stops. Nothing here should be read as a statement that Part B does or does not cover them, in either direction.

What do I pay for outpatient care?

Two charges, not one. You usually pay 20 percent of the Medicare-approved amount for the doctor's services after the yearly Part B deductible. Then you usually pay the hospital a separate copayment for each service you get in a hospital outpatient setting.

The second charge behaves differently from the first. It is not a share of anything you have already been quoted. It is a copayment to the hospital, charged for each service, on top of what you pay the doctor. Certain preventive services do not carry it.

Medicare states the consequence rather than leaving you to work it out. You may pay more for outpatient services you get in a hospital outpatient setting than you would pay for the same care in a doctor's office.

It then puts a ceiling on that copayment. In most cases, the copayment cannot be more than the Part A hospital stay deductible for each service.

Read that ceiling twice, because Medicare publishes it in two places and only one of them finishes the sentence. Call it the Unfinished Sentence. On the costs page, the rule reads: in most cases, your copayment will not be more than the Part A hospital stay deductible amount. It stops there, and the words critical access appear nowhere in that page's Part B table.

On the outpatient services page, the same rule carries a second sentence. If you get hospital outpatient services in a critical access hospital, your copayment may be higher and may exceed the Part A hospital stay deductible.

Both facts are the government's. Noticing that one page's hedge is the other page's named exception, and saying which page carries which, is ours. Neither page says what a critical access hospital is, and neither tells you how to find out whether you are in one, so this page names the split and stops there rather than filling the gap with a reason.

Medicare also publishes what actually sets your number, and only one of the five is the service. Specific amounts you could owe depend on other insurance you may have, how much your doctor charges, whether your doctor accepts assignment, the type of facility, and where you get your test, item or service.

Medicare also publishes what actually sets your number, and only one of the five is the service.

Its instruction on the same page is short. Ask your doctor or health care provider how much your test, item or service will cost.

Is there an out-of-pocket limit?

No. Medicare states plainly that there is no yearly limit on what you pay out of pocket, unless you have supplemental coverage such as a Medicare Supplement Insurance policy, called Medigap, or you join a Medicare Advantage Plan. Nothing caps the total on its own.

That sentence sits above every part of Medicare on the costs page, before Part A, Part B or anything else is described. It is a statement about the program rather than about one benefit.

Set it beside the two charges in the section above and the shape of a Part B year becomes clear. The deductible is paid once each calendar year. The 20 percent share is not: it attaches to each covered service or item, every time. The hospital copayment is not either: it attaches to each service you get in a hospital outpatient setting.

So one of the three stops after it is paid, and two of them keep going as long as care keeps happening.

The per-service ceiling from the last section does not close that gap, and it is worth being precise about why. It limits what a single hospital copayment can be. It says nothing about how many of them a year can contain.

Medicare names two things that add a yearly ceiling, supplemental coverage and a Medicare Advantage Plan, and they are the exceptions written into the rule itself. How each one works, and what choosing between them involves, belongs to the Costs and Plans sections of this publication rather than to a coverage page.

What counts as outpatient?

Medicare's covered outpatient hospital list answers it by example rather than by definition. It includes emergency or observation services, which may include an overnight stay, same-day surgery, lab tests billed by the hospital, X-rays and other radiology billed by the hospital, medical supplies, and preventive and screening services.

Notice what the list does not do. It never defines outpatient. The nearest thing to a definition on this page is the condition attached to the benefit itself: services you get as an outpatient from a hospital that takes Medicare.

The first item is the one worth reading slowly. Emergency or observation services sit on the list of covered outpatient services, and Medicare's own wording says those services may include an overnight stay in the hospital.

A night in a hospital bed can therefore sit inside Medicare's outpatient list. What decides which side of that line you are actually on during a stay, and what the hospital has to tell you about it, is a separate question with its own page in this section. This page is about what the benefit covers, not about how your status gets set.

Two items on the list carry the same three extra words, and they are doing real work. Lab tests billed by the hospital. X-rays and other radiology services billed by the hospital.

Medicare attaches that qualifier to those two lines and to no others on the list, and it does not explain it anywhere on either of this page's sources. What can be said honestly is that the phrase is there, that it is there twice, and that it sits on the two items whose costs split in opposite directions.

What about lab tests and imaging?

They split, and the split is on Medicare's own price list. Covered clinical laboratory services are priced at zero dollars. Everything else runs on the general rule, usually 20 percent of the cost for each covered service or item after you have paid the deductible.

Both belong to Part B. Lab tests billed by the hospital and X-rays and other radiology services billed by the hospital both appear on the same list of covered outpatient hospital services. Being covered is not the thing that separates them.

The price list is. One row prices covered clinical laboratory services at zero dollars, and no other row on the Part B table does anything similar.

What Medicare prices	What the costs page says you pay	The trap
Covered clinical laboratory services	Zero dollars	Assuming the deductible and the coinsurance apply here
Any other covered service or item	The usual coinsurance share, after the deductible	Reading "usually" as "always"
The same service in a hospital outpatient setting	That share, plus a hospital copayment	Comparing a hospital price with a doctor's office price

The third row is the layer this page keeps returning to. Imaging done in a hospital outpatient setting carries the 20 percent and the hospital's copayment, so the gap between the two rows above it is wider in a hospital than anywhere else.

One word in the zero-dollar line deserves the last say, and it is covered. Medicare prices covered clinical laboratory services at zero, and neither of this page's two sources says which laboratory services qualify. The zero is real and it is bounded, and the boundary is not published in either place a reader is likely to land.

What this means for you

Part B is the outpatient half of Original Medicare, and its cost has two layers rather than one. The 20 percent share is the layer Medicare states first. The hospital copayment on top, and the absence of any yearly ceiling, are the two that decide the size of the bill.

The scope question and the price question are not the same question, and this page answers the first one. What Part B costs each month and each year, and how Part A and Part B differ from each other, are carried by the Costs and Basics sections.

If one thing from this page is worth carrying into an appointment, it is Medicare's own instruction rather than anything written here. Ask what the test, item or service will cost, and ask where it will be delivered, because Medicare lists the type of facility among the five things that set your number.

FAQ

Does Part B cover prescription drugs you get as an outpatient?

Partly, and Medicare's own list puts the exception before the rule. Certain self-administered drugs and biologicals you get as part of your service or procedure, like certain injectable drugs, appear on Medicare's list of covered outpatient hospital services.

Then comes the general rule: Part B does not cover prescription and over-the-counter drugs you get in an outpatient setting, the ones Medicare calls self-administered drugs. Medicare adds a practical note beside it. For safety reasons, many hospitals have policies that do not allow patients to bring prescription or other drugs from home.

And it names a route. If you have Medicare drug coverage, called Part D, these drugs may be covered under certain circumstances, though you will likely need to pay out of pocket and submit a claim to your drug plan for a refund. Medicare's own instruction is to call your drug plan.

Why does the same service cost more in a hospital than in a doctor's office?

Because a second charge is added. Medicare states that in addition to the amount you pay the doctor, you will also usually pay the hospital a copayment for each service you get in a hospital outpatient setting. That copayment does not exist when the same service happens in a doctor's office.

Medicare states the consequence in its own words, on both of this page's sources: you may pay more for an outpatient service you get in a hospital than you would pay if you got the same service in a doctor's office. One exception is named. Certain preventive services do not carry a copayment.

Neither source publishes the copayment amounts, and neither says which services carry the larger ones, so the size of the difference is not something this page can state. Medicare's instruction on the same page is to ask what your test, item or service will cost.

Do preventive services work differently under Part B?

They do, on two separate charges, and Medicare states each exception in a different place on the same page. On the deductible: the Part B deductible applies, except for certain preventive services.

On the hospital copayment: you will usually pay the hospital a copayment for each service you get in a hospital outpatient setting, except for certain preventive services that do not have a copayment. Preventive and screening services also sit on Medicare's list of covered outpatient hospital services, so they are inside the benefit rather than an addition to it.

Two limits are worth reading carefully before relying on any of that. Both exceptions say certain preventive services rather than all of them, and neither of this page's sources lists which ones qualify. The scope of the word certain is not published in either place.

What decides the exact amount I owe for a test or service?

Medicare publishes a list of five things, and not one of them is your diagnosis. Specific amounts you could owe depend on other insurance you may have, how much your doctor charges, whether your doctor accepts assignment, the type of facility, and where you get your test, item or service.

Set that list against the 20 percent rule and the connection is direct. The 20 percent is a share of the Medicare-approved amount, and it holds as long as your doctor or health care provider accepts the Medicare-approved amount as full payment, which Medicare calls accepting assignment.

Two of the five name where the care happens rather than what it is: the type of facility, and where you get your test, item or service. Four of the five are about who bills you and where. The fifth is about what other coverage you already hold.

What does covered mean on Medicare's zero-dollar laboratory line?

Medicare's costs page prices covered clinical laboratory services at zero dollars, and the word doing the most work in that line is covered. Neither of this page's two sources says which laboratory services qualify.

The coverage page for outpatient hospital services lists laboratory tests billed by the hospital among the services Part B covers, and it attaches that same phrase, billed by the hospital, to X-rays and other radiology services, without defining that either.

So the zero-dollar line is real and it is bounded, and the boundary is not published in either place a reader is likely to land. This publication does not fill that gap with an estimate.

What the two sources do support is narrower and still useful: a laboratory service that is covered is priced at zero, and everything else on the Part B table runs on the usual 20 percent.