A Medicare number is an identifier and proof of medical insurance that beneficiaries must provide in order to receive treatment at a doctor's office or hospital, according to AARP. An individual's Medicare number is usually his Social Security number followed by one or two additional digits.
Medicare is the United States health care insurance program for citizens over the age of 65, states the Social Security Administration. Citizens younger than 65 can qualify for Medicare under certain circumstances, such as disabilities or permanent kidney failure. The program assists with the cost of health care, but it does not cover all medical or long-term care expenses.