It depends. If you are age 65 or older and you (or your working spouse) have payed Medicare payroll taxes for at least 10 years, you are likely eligible for no cost Medicare inpatient hospital insurance (Part A). You should sign up for Medicare hospital insurance (Part A) 3 months before your 65th birthday, whether or not you want to begin receiving retirement benefits.
If you are already receiving Social Security Benefits, enrollment is automatic.
If you have credible employer health insurance you may be able to delay your enrollment as long as you want with no penalties. Yes, you can work until you’re 65 or 95!