Medicare enrollment begins three months before your 65th birthday and continues for 7 months. If you are currently receiving Social Security benefits, you don't need to do anything. You will be automatically enrolled in Medicare Parts A and B effective the month you turn 65.
People with group health policies through their employer generally do not have to sign up for Medicare when they turn 65. They, or you in this case, can keep your employer coverage until you retire. You will then have eight months within which to sign up for Medicare without facing any penalties for late enrollment.
If you do not have employer insurance and you turn down Part B, you may have to pay a hefty premium penalty when you do sign up. If you are 65, but are not receiving Social Security retirement benefits or Railroad Retirement benefits, youwill need to actively enroll in Medicare.