Kay was shown a straight red card during the Dons' 2-1 npower League One defeat to Yeovil at Huish Park on January 29 following a clash with Glovers striker Paddy Madden.
But an FA Disciplinary Committee upheld the decision and the 30-year-old centre-back will now be unavailable for selection until February 23 when Karl Robinson's side travel to Carlisle.
Kay served the first game of his ban as the Dons were beaten 3-0 at home by Bournemouth on Saturday.
He will miss further league fixtures away at Oldham (February 9) and Doncaster (February 12) as well as the club's historic FA Cup fifth-round tie with Barnsley at stadium:mk on February 16.
- Sports & Recreation
- Karl Robinson