Medicare Part B is viewed as medical insurance, and is the second part of Original Medicare. Once you’re enrolled in Medicare Part A, you can choose to also enroll in Part B to have both parts of Original Medicare, or you can choose to stay with just Part A.
However, if you do want to enroll in Part B, it’s best to enroll as soon as you become eligible during your Initial Enrollment Period. If you delay your enrollment in Part B past this period, you can enroll during the General Enrollment Period (January 1 – March 31) but you will have to pay a late enrollment penalty that will be permanently added to your Part B premium.
It’s also possible to be automatically enrolled in both Part A and Part B if you are receiving Social Security income benefits.