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

Medicare Part B pays for services like office visits to your doctor, lab tests, X-rays, and outpatient surgery — the care you receive outside a hospital. It is separate from Part A, which covers hospital stays. Most people who get Social Security at 65 are automatically enrolled in Part B, but you pay a monthly premium for it, and the amount depends on your income.

Part B is not automatic the way Part A is. If you do not sign up when you first become may be able to access at 65, you may face a permanent penalty on your premium. The enrollment window is three months before the month you turn 65, the month itself, and three months after — a seven-month window total. If you miss it and do not have other health coverage, you will pay more for Part B for as long as you have Medicare.

Key Takeaways

  • Part B covers doctor visits, lab work, imaging, and outpatient procedures, but not hospital stays or prescription drugs.
  • You pay a monthly premium for Part B, and the amount is based on your income from two years prior — higher earners pay more.
  • You are automatically enrolled in Part B at 65 if you are already receiving Social Security, but you can decline it in writing if you have other coverage.
  • Missing the enrollment window when you turn 65 results in a permanent 10 percent penalty added to your premium for each year you were late.
  • Part B has an annual deductible and you pay 20 percent of the cost for most services after you meet it.

What Part B actually covers and what it does not

Part B covers the doctor's office visit itself, blood tests, EKGs, X-rays, ultrasounds, CT scans, and outpatient surgery at a hospital or surgery center. It also covers some preventive care with no cost to you — a yearly wellness visit, certain cancer screenings, and vaccines. Durable medical equipment like wheelchairs, walkers, and oxygen equipment is covered under Part B as well.

Part B does not cover prescription drugs — that is Part D. It does not cover dental, vision, or hearing care. Hospital stays are Part A. Nursing home care is Part A if you go there directly from a hospital stay of at least three days; otherwise it is not covered by Medicare at all. Mental health visits are covered, but only as outpatient care.

How much you pay in premiums and what your income has to do with it

The standard Part B premium in 2024 is $164.90 per month, but your actual premium depends on your modified adjusted gross income (MAGI) from two years before. If you earned more than a certain threshold, you pay a higher premium — this is called an Income-Related Monthly Adjustment Amount, or IRMAA. The thresholds and surcharges change each year.

The income used is from your tax return from two years prior. If you were married and filed jointly, both spouses' income counts. If your income drops significantly — you retire, your spouse dies, you have a major loss — you can ask Medicare to use your current year income instead. You have to file a form called the Life-Changing Event form within 60 days of the event.

Even if you do not owe income tax, Medicare will look at your tax return to calculate IRMAA. If you have not filed a return in years, Medicare will estimate your income, and you may end up paying more than you should. Filing a return, even if you do not owe, protects you from overpaying.

The deductible and what you pay when you see a doctor

Part B has an annual deductible — in 2024 it is $240. You pay this amount out of pocket before Part B starts paying anything. After you meet the deductible, you typically pay 20 percent of the Medicare-approved amount for most services, and Medicare pays 80 percent.

The key phrase is "Medicare-approved amount." If your doctor does not accept Medicare, or charges more than Medicare allows, you may owe the difference. Doctors who accept Medicare and agree to charge only the Medicare-approved amount are called "participating providers." Before you schedule an appointment, ask whether the doctor participates in Medicare and accepts assignment.

Some services have different cost-sharing. Preventive care covered by Part B — like a yearly wellness visit or a colonoscopy for screening — costs you nothing after you meet your deductible. Mental health visits cost 20 percent after the deductible, the same as other office visits.

Automatic enrollment and what happens if you turn it down

If you are already receiving Social Security when you turn 65, Medicare automatically enrolls you in Part A and Part B. You do not have to do anything. Your Part B premium is deducted from your Social Security check each month.

You can decline Part B in writing if you have other health coverage — usually through an employer or a spouse's employer. To decline, you must contact Social Security and submit a form. Keep a copy of the form and the date you submitted it. If you decline and later change your mind, you can enroll during the General Enrollment Period (January 1 through March 31 each year), but you will pay a penalty.

If you are not yet receiving Social Security when you turn 65, you must sign up for Medicare yourself through Medicare.gov or by calling 1-800-MEDICARE. The enrollment window is the same: three months before, the month of, and three months after your 65th birthday.

The penalty for missing the enrollment window

If you do not enroll in Part B during your initial enrollment period and you do not have other may have access to coverage, you pay a permanent penalty. The penalty is 10 percent of the standard premium for each full year you were may be able to access but not enrolled. If you were may be able to access for three years and did not sign up, your premium is 30 percent higher than the standard amount, and that surcharge stays with you for life.

The only exceptions are if you had coverage through an employer (yours or a spouse's) or through TRICARE or the Veterans Administration. If you had one of these, your initial enrollment period is extended — it does not end until eight months after your coverage ends. You must sign up within that window to avoid the penalty.

How Part B works with other insurance

If you have a Medigap policy (also called supplemental insurance), it works alongside Part B. You pay your Part B premium and your Medigap premium, and Medigap covers some or all of the 20 percent you would otherwise owe. The Medigap policy you choose determines how much it covers.

If you have a Medicare Advantage plan (Part C), it replaces Part B. You do not pay the Part B premium separately; instead you pay the Advantage plan's premium. The Advantage plan covers the same services as Part B but often with different costs and provider networks.

If you have coverage through an employer or a spouse's employer, you may be able to delay Part B enrollment without penalty. This is called "creditable coverage." When your employer coverage ends, you have eight months to enroll in Part B without penalty. Your employer's benefits office can tell you whether your plan qualifies.

Frequently Asked Questions

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

If you are already receiving Social Security, you are automatically enrolled in Part B. You can decline it in writing if you have other health coverage, but you must do this before the enrollment period ends. If you are not yet receiving Social Security, you must sign up yourself during your enrollment window or face a permanent penalty.

What if I work past 65 and have health insurance through my job?

You can delay Part B enrollment without penalty as long as your employer coverage is active. When you retire and your coverage ends, you have eight months to enroll in Part B. Your employer's human resources or benefits office can confirm whether your plan qualifies as creditable coverage.

Can I change my mind about Part B after I decline it?

Yes, but only during the General Enrollment Period from January 1 through March 31 each year. If you enroll late, you will pay a 10 percent penalty on your premium for each year you were may be able to access but not enrolled. The penalty is permanent.

Why does Medicare look at my income from two years ago?

Medicare uses prior-year income because it takes time to process tax returns and calculate premiums. If your income has dropped significantly since then — you retired, your spouse died, or you had a major loss — you can report the change and ask Medicare to use your current income instead. You must file a Life-Changing Event form within 60 days.

What happens if I cannot afford the Part B premium?

If your income is low, you may be able to get help paying your Part B premium through your state's Medicaid program or through a program called the Medicare Savings Program. Contact your state Medicaid office or call 1-800-MEDICARE to learn whether you may have access to and how the process works.