The short answer
Medicare Part B covers preventive and screening services, including exams, vaccines, lab tests and screenings. You pay nothing for most of them if you see a health care provider who accepts assignment. Medicare's own page warns that a service it does not cover, or a covered service given too frequently, can still cost you.
You booked something Medicare calls free, and a bill arrived anyway. The service may have been covered the whole time. Medicare prints two reasons on the same page as the promise, in a single sentence near the bottom.
What preventive services does Medicare cover?
Medicare Part B covers preventive and screening services. Medicare's own list runs to twenty four entries, and four of those open into lists of their own. It covers exams, vaccines, lab tests and screenings, plus programs for health monitoring, and counseling and education.
Medicare's definition is doing more work than it looks. Preventive services help you stay healthy, find health problems early, determine the most effective treatments, and prevent certain diseases.
Read the third item again. Determining the most effective treatments is not prevention in the ordinary sense, and it sits inside the definition anyway.
The list itself is the clearest map of the benefit. In Medicare's own order it opens with abdominal aortic aneurysm screenings, alcohol misuse screenings and counseling, and bone mass measurements, then two cardiovascular entries and cervical and vaginal cancer screenings.
Colorectal cancer screenings come next, then counseling to prevent tobacco use and tobacco-caused disease, depression screenings, diabetes screenings and diabetes self-management training. After those come glaucoma screenings, two hepatitis screening lines, HIV services, lung cancer screenings, mammograms, medical nutrition therapy, the Medicare Diabetes Prevention Program, obesity behavioral therapy, prostate cancer screenings, and sexually transmitted infections screenings and counseling.
Two entries near the end of that list are not screenings at all, and they are the ones this section of the publication is built around.
The first is preventive visits, which opens into two: the "Welcome to Medicare" preventive visit and the yearly "Wellness" visit. Both sit inside the preventive benefit rather than beside it.
The second is vaccines. Medicare files four of them here under Part B: COVID-19 vaccines, flu vaccines, hepatitis B vaccines and pneumococcal vaccines. Which shots fall on the Part B side and which fall elsewhere is its own question with its own page in this section.
Which ones are free?
Most of them, and the condition matters more than the word. You pay nothing for most preventive services if you get the services from a health care provider who accepts assignment. Medicare wrote "most" rather than "all", and it wrote a condition about the provider rather than about the service.
That single sentence carries two limits, and neither is about what you booked.
The first is the word most. Medicare does not publish, on this page, which preventive services fall outside it. The list is not marked up to show which entries are the exceptions.
The second is the condition. The rule turns on whether the provider accepts assignment, which is a fact about who you see rather than about what they do. What accepting assignment means, and what changes when a provider does not, is carried in this publication's Basics section.
| What decides it | What Medicare's page says | The trap |
|---|---|---|
| The provider | You pay nothing if they accept assignment | Assuming the service alone decides |
| Whether Medicare covers it | An uncovered service can still be billed | Reading the visit label as full cover |
| How often you had it | Too frequently can add cost | Reading covered as unlimited |
So the honest version of "free" is conditional in three directions at once. The service has to be one Medicare covers, the provider has to accept assignment, and the timing has to sit inside whatever interval Medicare offers.
The next section is about the third one.
How often can I get each one?
It depends on the service. On the list this publication checked on August 13, 2026, Medicare does not gather the intervals in one place and publishes no combined schedule. Each entry links to its own page, and the frequency lives there.
That is our finding rather than Medicare's statement, and it is the reason this section is short rather than long.
What this page's own sources do state is one interval and one limit of a different kind, and the two are worth setting side by side because they behave nothing alike.
The interval is a clock. The "Welcome to Medicare" preventive visit is covered once within the first 12 months you have Part B. Miss that window and the visit is gone, not delayed.
The limit of a different kind is a gate. Hepatitis B vaccines are covered if you are eligible, and eligibility means meeting at least one of three conditions.
You have never gotten a complete series of hepatitis B vaccines. You do not know your vaccination history. Or you have a health condition or situation putting you at medium or high risk for hepatitis B, and Medicare gives three examples of that: diabetes, End-Stage Renal Disease, or living with someone who has hepatitis B.
A clock runs out. A gate either opens or it does not, and it can open for one person and stay shut for the next on the same day.
Both matter for money rather than only for scheduling. The next section shows how.
What turns a free visit into a billable one?
Two things, and Medicare names both in one sentence. Your doctor may recommend services that Medicare does not cover or offers too frequently. This could end up in additional costs for you. Make sure to ask your doctor about the reasons for these recommendations and what Medicare will actually cover.
Read that sentence twice. It contains two different failures wearing one coat. Call the second one The Second Trigger.
The first trigger is the familiar one. Something happens that Medicare does not cover, and it is billed. The service was never inside the benefit.
The second trigger is not like that at all. The service IS covered. Medicare offers it, on its own list, at its own interval. It is given more often than that interval allows, and the cost lands on you.
So a bill can arrive for something that was on the list, from a provider who accepts assignment, for a service Medicare pays for in the ordinary case. Nothing about the service changed. The calendar did.
That sentence is Medicare's, and so is the fact that it prints it word for word on the preventive page and on each of the vaccine pages this publication read. Noticing that the benefit's only warning is boilerplate, and that one of its two triggers is a service that was covered all along, is ours.
Of the two, the second is the one a reader is least likely to have been warned about, and it is the one that can arrive without anything about the service having changed.
What no source states, and what this page will not supply, is how often either trigger fires, what a too-frequent service costs, or which services carry which intervals.
What is the Welcome to Medicare visit?
It is a one-time preventive check-up, covered once within the first 12 months you have Part B. It reviews your medical history, gets you up to date on important screenings and vaccines, and covers your family history. Medicare states plainly that it is not a comprehensive physical exam.
The visit has a defined content list rather than an open agenda, and reading it tells you what to expect to be asked.
Your provider reviews your medical and social history related to your health. They give you information about preventive services, including certain screenings and vaccines. They review your potential risk factors for substance use disorder, such as alcohol and tobacco use, and refer you for treatment if needed. They also give you referrals for other care as needed.
They calculate your body mass index, give you a simple vision test, and review your potential risk for depression. They offer to talk with you about creating advance directives. Those are legal documents recording your wishes about future medical treatment, in case you are ever unable to make decisions about your care.
The visit ends with something physical. You get a written plan, like a checklist, telling you what screenings, vaccines and other preventive services you need.
Medicare also names what to bring: medical records including immunization records, family health history, and a list of any prescription drugs, over-the-counter drugs, vitamins and supplements you take, how often you take them, and why.
One clause applies only to some readers and it is specific. If you have a current prescription for opioids, your provider will review your potential risk factors for Opioid Use Disorder, evaluate your pain level and current treatment plan, give you information on non-opioid treatment options, and refer you to a specialist if appropriate.
How do I avoid a surprise charge?
Medicare answers this itself, inside the same warning that names the two triggers. Ask your doctor about the reasons for these recommendations and what Medicare will actually cover. That instruction is the government's, it sits beside the risk it addresses, and it recommends no service.
The wording repays attention. It asks two questions rather than one.
The first is about the reason a service is being recommended. The second is about what Medicare will cover, which is a separate fact that the reason does not settle.
There is also a route that does not involve asking anyone. You can log in to your secure Medicare account to check your preventive services, which is where the intervals attached to your own record live.
This publication recommends nothing here. Medicare names the risk, prints one instruction, and points at your account, and that is the whole of what this page's own sources say.
What this means for you
Preventive coverage under Part B is wide, and the word carrying the most weight in its cost rule is "most". You pay nothing for most preventive services when the provider accepts assignment, which makes free a property of the circumstances rather than of the service you booked.
Two things end that, and only one of them is intuitive. A service Medicare does not cover is billed. A covered service given more often than Medicare offers it is also billed, and that is the one worth carrying into an appointment.
If one thing here is worth taking with you, it is Medicare's own question rather than anything written on this page. Its instruction is to ask your doctor about the reasons for a recommendation and what Medicare will actually cover.
FAQ
What counts as a preventive service under Medicare?
Medicare defines them by what they do rather than by naming a department. Preventive services help you stay healthy, find health problems early, determine the most effective treatments, and prevent certain diseases.
They include exams, vaccines, lab tests and screenings, and they also include programs for health monitoring, and counseling and education to help you take care of your own health. The published list carries twenty four entries, and four of those open into lists of their own, so the number of individual services is larger than the number of lines.
The entries run from screenings for specific conditions through to two whole categories that are not screenings at all: preventive visits, and vaccines. That last pair is why a benefit people picture as tests also contains appointments and shots.
Does free really mean free?
It means free under conditions, and Medicare states them rather than hiding them. You pay nothing for most preventive services if you get the services from a health care provider who accepts assignment.
Two words there do the limiting. "Most" tells you the rule has exceptions, and this page's source does not mark which entries on its list are the exceptions. "Accepts assignment" attaches the rule to the provider rather than to the service, so the same screening can be free with one provider and not with another.
Medicare then names two things that add cost even inside the benefit: a service it does not cover, and a covered service given too frequently. So the service being on the list is necessary for it to be free, and on its own it is not enough.
What happens at the Welcome to Medicare visit?
It is a one-time check-up in your first 12 months of Part B, and Medicare publishes its contents. Your provider reviews your medical and social history related to your health. They give you information about preventive services, including certain screenings and vaccines.
They review your potential risk factors for substance use disorder, such as alcohol and tobacco use, and refer you for treatment if needed. They also give you referrals for other care as needed. They calculate your body mass index, give you a simple vision test, review your potential risk for depression, and offer to talk about advance directives.
You leave with a written plan, like a checklist, of what screenings and vaccines you need. Medicare asks you to bring medical records including immunization records, your family health history, and a list of everything you take with how often and why.
Does eligibility ever limit a preventive service?
No, and hepatitis B vaccines are the clearest published example of why. Medicare covers them if you are eligible, and eligibility means meeting at least one of three conditions. You have never gotten a complete series of hepatitis B vaccines.
You do not know your vaccination history. Or you have a health condition or situation putting you at medium or high risk for hepatitis B, and Medicare gives three examples of that: diabetes, End-Stage Renal Disease, or living with someone who has hepatitis B.
So a service can sit on the preventive list and still be closed to a particular reader, because the entry carries an eligibility test underneath it. That is a different mechanism from an interval. Medicare states the three conditions and states that meeting at least one of them is what makes you eligible.
How can I check which preventive services I am due?
Medicare points at your own record rather than at a general schedule. You can log in to your secure Medicare account to check your preventive services.
That matters because the intervals are not published together in one place: each entry on the preventive list links to its own page, and the frequency for that service lives there. This publication checked the list on August 13, 2026 and found no combined schedule on it.
The account route is useful for a second reason, which is that timing is one of the two things Medicare names as turning a covered service into a billed one. Medicare's own instruction alongside that warning is to ask your doctor about the reasons for a recommendation and what Medicare will actually cover.
