The second Medicare card is the one I use now. There will be a third Medicare card in my future, when I begin Social Security based on my own Social Security record. When I turned age 66, a second Medicare card came into my life. When I start receiving Social Security based on my own record, it will trigger the issuance of my third Medicare card. I will stop using the second Medicare card I have now.

Source: Forbes January 13, 2017 15:04 UTC