You can enroll in Medicare when you turn 65, if you are not receiving Social Security or Railroad Retirement benefits. You can enroll during the Initial Enrollment Period, which is seven months long, and includes the three months before you turn 65, your birthday month and the three months after you turn 65. If you do not enroll when you are eligible, you will have to pay a penalty when you do sign up. People with disabilities and people with End Stage Renal Disease, or ESRD (permanent kidney failure requiring dialysis or transplant), can sign up for Medicare regardless of age.  To find out if a disability qualifies for Medicare, you’ll need to speak with Social Security directly. If a disability qualifies you for Medicare, you must first sign up for Social Security benefits before being considered for Medicare.