Ronaldo to miss AC Milan rematch
The Portuguese forward, who has been out since aggravating an injury to his right ankle while on international duty three weeks ago, had been targeting a return for the trip to Italy.
Ronaldo will undergo another test in a week's time, Real said in a statement on their website.
Olympique Marseille's Souleymane Diawara caught Ronaldo's ankle during his side's 3-0 Champions League defeat at the Bernabeu on September 30.
Manuel Pellegrini's side, who had won every match this season before Ronaldo's injury, have since slumped to three defeats, a draw and only one victory in all competitions.
Real, level on six points with Champions League Group C leaders Milan after three games, travel to the San Siro next Tuesday.