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Medicare Part B – Medical Insurance

Part B (medical insurance) helps pay for doctor's office visits and services, lab tests, and most outpatient care. Most people pay a monthly premium for Part B.

Part B enrollment:

  • You can enroll in Part B during your Initial Enrollment Period. This is a seven-month period — the three months before your birthday month, your birthday month, and the three months after your birthday month.
  • If you decline Part B during your Initial Enrollment Period and enroll during the General Enrollment Period, you may pay a penalty. The monthly premium for Part B goes up 10% for each 12-month period that you could have had Medicare coverage but didn’t sign up for it. The penalty increases as Medicare premiums increase.
  • If you decline Part B during your Initial Enrollment Period because of coverage due to active employment for a company with 20 or more employees, you should enroll during your Special Enrollment Period.

Be sure to enroll in Part B if you:

  • Are retired
  • Are not working
  • Have COBRA or retiree health coverage
  • Have a group health plan that pays second after Medicare pays

If your work status changes, call the Social Security Administration at 1-800-772-1213. Ask how your change in work status may affect your Medicare coverage. TTY users should call 1-800-325-0778.

Play this video to learn about signing up for Medicare Part B.

  • Read Transcript

    Part B (Original Medicare)


    What is it?

    Along with Medicare Part A, Medicare Part B is known as Original Medicare. It is medical Insurance that helps cover services and supplies not covered by Part A. You pay a monthly premium for Part B coverage.

    What are the details?

    The first time you can enroll in Medicare Part B is during the Initial Enrollment Period. It is a seven-month window that starts three months before your 65th birthday month and ends three months after your birthday month. If you miss it, you can still sign up during a General Enrollment Period from January 1 through March 31, but you may have to pay a late enrollment penalty.

    If you keep working after you turn 65 and get insurance through your employer, you can hold off enrolling in Part B until you retire. An eight-month Special Enrollment Period will start on the date that your employment or group coverage ends, whichever comes first. Part B coverage starts the first day of the month of your 65th birthday.

    What else should I know?

    • Are you already getting Social Security or Railroad Retiree benefits? If you are, you will be automatically signed up for Part B.
    • You can wait to enroll in Part B if you are covered through your (or your spouse's) current employer. But once employment ends, you have eight months to sign up for Part B without a penalty.
    • If you decide NOT to enroll in Part B coverage, follow the directions in your Medicare package. If you didn't get the package, call the Social Security Administration and ask for one.

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Last Updated: Aug. 02, 2023