Players involved in the Champions League may be visited by drug-testers at their homes.
Uefa has introduced out-of-competition drug testing, which means players can be tested anywhere in the eight days before a Champions League match.
“Clubs entering the Champions League this season have had to agree to this rule,” a Uefa spokesman told BBC Sport.
“We are following sports like athletics and cycling and now we can test players at training grounds or at their homes.”
Football as come under pressure from the World Anti-Doping Agency to increase testing and there have been suggestions that the sport will be omitted from the Olympics unless more testing is carried out.
Under the rules introduced by Uefa for this season’s Champions League, clubs will be required to tell the governing body of their players whereabouts prior to games.
The Uefa spokesman said: “This will be done completely randomly and the element is surprise. We can call upon any player, at any time.
“Clubs have to tell us the location of all their players in the eight days before a game and we must be able to reach players at any time. No notice will be given to the players.”
