Medicare Part B is the medical insurance piece that covers doctor visits and outpatient care

Medicare Part B pays for services from doctors, specialists, and hospital outpatient departments. It covers office visits, lab tests, X-rays, surgery done outside a hospital, mental health care, and preventive screenings. Part B is optional — you do not have to take it — but most people do because the cost is low compared to what these services would otherwise run.

Part B is separate from Part A, which covers hospital stays. You can have Part A without Part B, or Part B without Part A, though most people have both. If you delay signing up for Part B when you first become may be able to access at 65, you will pay a higher monthly premium for as long as you have Medicare, so the timing matters.

Key Takeaways

  • Part B covers doctor office visits, specialist care, lab work, imaging, and preventive screenings, but not prescription drugs or routine dental or vision care.
  • You pay a monthly premium (the amount varies by income), a yearly deductible, and then 20 percent of the cost for most services after the deductible is met.
  • If you do not sign up for Part B when you turn 65, you will pay a permanent penalty on your monthly premium unless you have other health insurance that counts as creditable coverage.
  • Medigap and Medicare Advantage plans can reduce what you pay out of pocket, but they work differently and cover different things.

What Part B actually pays for

Part B covers the doctor side of health care. That means office visits with your primary care doctor or any specialist — cardiologist, rheumatologist, neurologist, and so on. It pays for lab work ordered by your doctor, imaging like X-rays and ultrasounds, and procedures done in an outpatient surgery center or hospital outpatient department.

Part B also covers preventive care at no cost to you: annual wellness visits, cancer screenings, diabetes screenings, heart disease screenings, and vaccines like flu and pneumonia shots. Mental health visits with a psychiatrist, psychologist, or licensed counselor are covered. Physical therapy and occupational therapy are covered if your doctor orders them for a medical reason.

Part B does not cover prescription drugs (that is Part D), routine dental work, routine eye exams or glasses, hearing aids, or most routine foot care. It does not cover cosmetic surgery or experimental treatments. If you need any of those things, you pay out of pocket or through a separate plan.

How much you pay each month and when

Part B has three layers of cost: a monthly premium, a yearly deductible, and coinsurance.

The monthly premium is taken directly from your Social Security check if you are already receiving benefits, or you pay it by mail or online if you are not. The standard premium amount changes each year. If your income is above a certain threshold, you pay a higher premium — Medicare calls this an Income-Related Monthly Adjustment Amount, or IRMAA. The income threshold and the surcharge amounts change yearly, so ask your Social Security office or Medicare what you will pay based on your specific income.

After you pay your monthly premium, you also have a yearly deductible — a set amount you must pay out of pocket before Part B starts paying. Once you have paid the deductible, Part B covers 80 percent of the approved cost for most services, and you pay 20 percent. Some preventive services have no deductible and no coinsurance — you pay nothing.

The approved cost is what Medicare decides a service is worth, not what the doctor's office charges. If a doctor charges more than the approved amount, you may owe the difference, though most doctors accept Medicare's approved amount as full payment.

When to sign up and what happens if you miss the important date

You become may be able to access for Medicare at 65. You can sign up during your Initial Enrollment Period, which is the three months before the month you turn 65, the month you turn 65, and the three months after. If you sign up during this window, your coverage starts on the first day of the month you turn 65 (or the first day of the following month if you sign up in the month you turn 65).

If you miss this window and do not have other health insurance that counts as creditable coverage, you will pay a late enrollment penalty on your Part B premium. The penalty is 10 percent of the standard premium for each full year you were may be able to access but did not sign up. That penalty stays on your premium for as long as you have Part B — it does not go away after a few years. So if you delay five years, you pay 50 percent extra on your premium forever.

The exception is if you have health insurance through your job or your spouse's job. If that coverage is creditable — meaning it is at least as good as Medicare — you can delay Part B without penalty as long as you are covered. When you leave that job or lose that coverage, you have eight months to sign up for Part B without penalty. You will need to show proof that you had creditable coverage.

How Part B works with other coverage

Part B is the foundation, but you have choices about what goes on top of it. Some people add a Medigap policy (also called Supplemental Insurance), which is private insurance that pays some or all of the 20 percent coinsurance you would otherwise owe. Others choose Medicare Advantage, which is an alternative to Original Medicare that Part B is part of — with Advantage, you get Part A and Part B coverage through a private insurance company instead of the government, usually with lower out-of-pocket costs but a narrower network of doctors.

If you have Medicaid (the state program for low-income people), it may pay your Part B premium and some of your out-of-pocket costs. If you are a veteran, you may have VA coverage that works alongside Medicare. The rules for how these programs coordinate are different for each one, so ask your state Medicaid office or the VA what you owe when you have both.

What to ask your doctor and Medicare

Before a procedure or test, ask your doctor whether it is covered by Part B and whether you will owe anything. Medicare publishes a list of covered services, but coverage rules can be specific — for example, Part B covers some physical therapy but not unlimited amounts, and coverage depends on whether your doctor says it is medically necessary.

If your doctor orders something and you are not sure whether Part B will pay, call Medicare at 1-800-MEDICARE (1-800-633-4227) and give them the service code. They can tell you whether it is covered and what you might owe. You can also ask your doctor's office to check with Medicare before the service happens, so you are not surprised by a bill afterward.

If you receive a bill you think is wrong, ask the provider for an itemized statement and compare it to what Medicare says it approved. You can file an appeal with Medicare if you think you were charged incorrectly.

When to call Medicare or your doctor

Call Medicare if your premium amount seems wrong, if you are unsure whether a service is covered before you have it done, or if you receive a bill you do not understand. Call your doctor if you have questions about whether a test or procedure is necessary or whether there are less expensive alternatives.

If you are having chest pain, difficulty breathing, or other signs of a medical emergency, call 911 — Part B covers emergency room visits, and you can sort out the billing afterward.

Frequently Asked Questions

Do I have to take Part B when I turn 65?

No, Part B is optional. But if you do not sign up and do not have other creditable health insurance, you will pay a permanent 10 percent penalty on your premium for each year you delay. Most people sign up because the penalty makes it expensive to wait.

What if my doctor charges more than Medicare approves?

Most doctors accept Medicare's approved amount as full payment. If a doctor does not, you may owe the difference. Before you have a procedure, ask the office whether they accept Medicare's approved amount. If they do not and you cannot afford the extra cost, you can see a different doctor.

Does Part B cover my prescription medications?

No. Prescription drug coverage is Part D, which is separate. You can add Part D when you first sign up for Medicare or during the annual open enrollment period. If you do not sign up when you are first may be able to access, you may pay a penalty when you do.

Can I switch from Part B to Medicare Advantage and back?

You can switch during the annual open enrollment period (October 15 to December 7 each year) or during the Medicare Advantage open enrollment period (January 1 to March 31). Outside these windows, you can only switch if you have a may have access to life event, like moving out of your plan's service area.

What happens to my Part B coverage if I move to a different state?

Part B coverage follows you anywhere in the United States. Your monthly premium and deductible stay the same. If you have a Medigap policy or Medicare Advantage plan, you may need to switch to a plan available in your new state, because not all plans operate in all states.