The striker, 25, who has scored six goals this campaign, turned his ankle in training and is waiting to find out the severity of the injury.
He may now miss the trip to Burnley on Saturday.
Fellow striker Richard Cresswell has already been ruled out for three months with a knee ligament injury and Michael Ricketts is currently out on loan at Cardiff, leaving David Healy, Robbie Blake and Ian Moore as the only options up front.
Leeds have already ruled out the possibility of recalling Ricketts and may turn instead to the loan market if Hulse's injury proves serious.