Sign up for Medicare Part B by applying online at Social Security, visiting your local Social Security office or calling Social Security at 1-800-772-1213, as of August 2015, according to Medicare.gov. Alternatively, download the Medicare Part B application for enrollment, and return it to your local Social Security office, states the Centers for Medicare & Medicaid Services.
When applying for Medicare Part B, you are required to have Medicare Part A. Medicare automatically enrolls some people. If you receive automatic enrollment, you receive a red, white and blue Medicare card in the mail three months before your 65th birthday or your 25th month of disability payments, as stated by Medicare.gov. If you want to drop your automatic enrollment for Medicare Part B, follow the instructions with the card, and send back the card.
You need to sign up for Medicare Parts A and B if you are not already getting Social Security or Railroad Retirement Board benefits, advises Medicare.gov. You also need to sign up if you have end-stage renal disease or if you live in Puerto Rico, where seniors only receive automatic enrollment for Medicare Part A. After you enroll, you must pay your Part B premium every month for as long as you have Part B, even you don't use it.