The Scottish Football Association has rejected an appeal by Barry Douglas, over the red card he received against Ross County.
Douglas was dismissed after 64 minutes of the 1-0 defeat in Dingwall following a challenge on Ivan Sproule.
However, after reviewing the incident on Thursday at Hampden the SFA have upheld the original decision.
United will be without Douglas for their next two matches - against St Johnstone on Saturday, and next week's trip to Inverness.
But the 23-year-old will be available for the final game of the season when United host Scottish Champions Celtic on 19 May at Tannadice.