Part B covers doctor visits, outpatient care, and medical equipment — and you enroll separately from Part A

Medicare Part B is not automatic. Even if you have Part A (hospital insurance), you must take a separate step to enroll in Part B, or you will pay a penalty for every month you delay. The enrollment window depends on when you turn 65 or become may be able to access through disability. Missing your window means waiting until the next General Enrollment Period, which runs January 1 to March 31 each year — and your coverage will not start until July 1 of that year.

You enroll through Social Security, either online, by phone, or in person at a local office. The process takes about 15 minutes if you have your information ready. Part B has a monthly premium (the amount changes each year based on your income), and you choose whether to pay it monthly or have it deducted from your Social Security check.

Key Takeaways

  • Your Initial Enrollment Period is the three months before you turn 65, the month you turn 65, and the three months after — a seven-month window to enroll without penalty.
  • If you miss your Initial Enrollment Period, you can enroll during General Enrollment (January 1 to March 31), but your coverage starts July 1 and you pay a permanent 10 percent penalty on your premium.
  • You enroll through Social Security online at ssa.gov, by calling 1-800-772-1213, or at your local Social Security office — not through Medicare directly.
  • Part B premium amounts vary by income and change each year; you can choose to pay monthly or have the amount deducted from your Social Security benefit.
  • If you are still working and have employer health insurance, you may be able to delay Part B enrollment without penalty — ask your employer's benefits office about creditable coverage.

Understanding your enrollment window

Your Initial Enrollment Period is a seven-month window centered on your 65th birthday. It starts three months before the month you turn 65 and ends three months after. For example, if you turn 65 in June, your window opens in March and closes in September. You can enroll any time during those seven months, and coverage begins on the first day of the month you turn 65 (or the first day of the month after you enroll, whichever is later).

If you miss this window, you enter the General Enrollment Period, which runs January 1 to March 31 every year. Coverage under General Enrollment does not start until July 1 of that year, creating a gap. You also pay a permanent 10 percent increase to your Part B premium for each 12-month period you could have been enrolled but were not. This penalty stays with you for life, so enrolling late is costly.

There is one exception: if you have creditable coverage through an employer or union while you are still working, you can delay Part B without penalty. Creditable coverage means your employer plan covers at least as much as Medicare Part B. You must enroll within eight months of losing that coverage to avoid the penalty. Ask your employer's benefits office in writing whether your plan qualifies as creditable coverage, and keep their written answer.

How to enroll through Social Security

You do not enroll in Part B through Medicare.gov. Instead, you go through Social Security. The fastest route is online at ssa.gov. Log in to your Social Security account (or create one if you do not have one), navigate to "Manage Benefits," and look for the option to enroll in Medicare Part B. The form takes about 10 to 15 minutes.

If you prefer to enroll by phone, call 1-800-772-1213 (TTY 1-800-325-0778). Have your Social Security number, date of birth, and citizenship information ready. The call usually takes 10 to 15 minutes. You can also visit your local Social Security office in person — find the nearest one at ssa.gov/locator.

When you enroll, Social Security will ask whether you want your Part B premium deducted from your Social Security check each month or billed separately. Most people choose the deduction because it is automatic and you do not have to remember to pay. If you choose separate billing, Medicare will send you a bill each month.

Part B costs and what is covered

Part B has two costs: a monthly premium and an annual deductible. The premium amount changes each year based on your income from two years prior. In 2024, the standard premium is $164.90 per month for most people, but higher-income beneficiaries pay more. The deductible (the amount you pay out of pocket before Part B starts covering costs) is $240 per year in 2024, but this also changes annually.

Part B covers doctor office visits, preventive care like annual wellness exams and cancer screenings, outpatient surgery, mental health services, physical therapy, and durable medical equipment like wheelchairs and oxygen. It does not cover routine dental, vision, or hearing care — those require separate coverage. After you meet your deductible, you typically pay 20 percent of the cost for most services, and Medicare pays 80 percent.

If your income is below certain thresholds, you may may have access to for Extra Help or Medicaid to cover your Part B premium and deductible. Contact your state Medicaid office or call 1-800-MEDICARE to learn whether you may have access to.

What happens after you enroll

After you enroll, Social Security sends your information to Medicare. Within two weeks, you should receive a Medicare card in the mail showing your Part B coverage. Your coverage begins on the date Social Security confirms. If you enrolled during your Initial Enrollment Period, coverage usually starts the first day of the month you turn 65. If you enrolled during General Enrollment, coverage starts July 1.

Once you have your card, you can use it at any doctor, hospital, or clinic that accepts Medicare. Most do, but always ask before your visit. If a provider does not accept Medicare, you will pay the full cost out of pocket. You can search for Medicare-accepting providers at Medicare.gov/care-compare.

Your Part B premium will be deducted from your Social Security check starting the month your coverage begins (or the following month, depending on Social Security's processing). If you chose separate billing, your first bill arrives about two weeks after your coverage starts.

Common mistakes to avoid

The biggest mistake is missing your Initial Enrollment Period and not realizing it until after your 65th birthday. By then, you have already entered a penalty period. If you are within three months of turning 65, enroll now — do not wait. If you have already missed your window, you can still enroll during the next General Enrollment Period (January 1 to March 31), but understand that your coverage will not start until July 1 and you will owe the late penalty.

A second common mistake is assuming you are automatically enrolled in Part B when you turn 65. You are not. Part A (hospital insurance) is usually automatic if you are receiving Social Security benefits, but Part B requires you to take action. Check your Social Security account or call 1-800-772-1213 to confirm whether you have enrolled.

A third mistake is not reporting a change in income to Social Security. Your Part B premium is based on your income from two years ago. If your income drops significantly (due to retirement, job loss, or other reasons), you may may have access to for a lower premium. Contact Social Security to report the change and request a premium reduction.

If you have employer coverage or are not yet 65

If you are still working and have health insurance through your employer or union, you can delay Part B enrollment without penalty — but only if your plan is creditable coverage. Before you decline Part B, get written confirmation from your employer that your plan qualifies. If you later find out it does not, you will owe the late penalty.

If you are under 65 and on Social Security Disability Insurance (SSDI) or have End-Stage Renal Disease (ESRD), you are may be able to access for Medicare. You are automatically enrolled in Part A after 24 months of SSDI benefits (or when ready if you have ESRD). You must enroll in Part B separately using the same process described above — through Social Security, not Medicare.

Frequently Asked Questions

What if I turned 65 more than three months ago and did not enroll?

You missed your Initial Enrollment Period. You can enroll during the next General Enrollment Period (January 1 to March 31), but your coverage will not start until July 1 and you will pay a 10 percent permanent penalty on your monthly premium. If you are within three months of the next General Enrollment Period, contact Social Security when ready to confirm your options.

Can I enroll in Part B online right now?

Yes, if you have a Social Security account. Go to ssa.gov, log in, select "Manage Benefits," and look for the Medicare Part B enrollment option. If you do not have an account, you can create one at ssa.gov/myaccount. You can also call 1-800-772-1213 or visit a local Social Security office.

Do I have to take Part B if I have other insurance?

If your other insurance is creditable coverage through an employer or union, you can delay Part B without penalty. Get written confirmation from your employer first. If your coverage is not creditable (for example, if it is a short-term plan or discount plan), you should enroll in Part B to avoid the penalty.

What if I cannot afford the Part B premium?

You may may have access to for Extra Help or Medicaid to cover your premium and deductible. Contact your state Medicaid office or call 1-800-MEDICARE to learn whether you may have access to based on your income and resources.

When does my Part B coverage actually start?

If you enroll during your Initial Enrollment Period (the seven months around your 65th birthday), coverage usually starts the first day of the month you turn 65. If you enroll during General Enrollment (January 1 to March 31), coverage starts July 1 of that year. Your Medicare card arrives in the mail within two weeks of your coverage start date.