Medicare is the nation's largest health insurance program, covering nearly 40 million Americans age 65 or older, disabled, and/or experiencing end-stage renal disease. This website provides information and an online tool to help individuals determine whether or not they are eligible for Medicare, and to provide information about enrollment. If you are not a U.S. citizen or a lawfully admitted alien who has lived in the U.S. continuously for a five-year period, please contact Social Security at 1-800-772-1213 for your Medicare enrollment and eligibility instead of using this tool.