SOCIAL SECURITY ADMINISTRATION ALERT: If you decide to delay your Social Security benefits until after age 65, you should still apply for Medicare benefits within three months of your 65th birthday. If you wait longer, your Medicare medical insurance (Part B) and prescription drug coverage (Part D) may cost you more money.
Even if you have health insurance through an employer or former employer, you should still check to see whether you need to sign up for Medicare. Some health insurance plans change automatically at age 65.
If you are already getting Social Security benefits when you turn 65, your Medicare Hospital Benefits will start automatically.
Source: The Official Website of the U.S. Social Security Administration http://www.socialsecurity.gov/retire2/agereduction.htm