The substance, which is not on the banned list issued by the International Olympic Committee or the UK Sports Council, was revealed by a recent survey in The Independent to be in widespread use in the sport.
"We have been in constant touch with the Sports Council about creatine," the League's chief executive, Neil Tunnicliffe, said. "They have come back to us again this week and told us that it is OK, but we are going to contact our clubs to warn them to be very careful about recommending it to their players. If it turns out, in years to come, that it has all sorts of side-effects, players could sue clubs which have encouraged them to take it."
The League has also held talks with the Players' Association about the substance, which is also widely used in other sports to combat fatigue.
The president of the French Rugby Union, meanwhile, has expressed surprise at the IOC's recent decision not to place creatine on its list of banned substances. Bernard Lapasset has warned French players they face suspension for taking creatine, even though his call to the IOC to have it banned at the Five Nations' Championship and the World Cup has gone unheeded.
"I admit I am a little surprised by the decision of the IOC not to class creatine as a doping product," Lapasset said. "We denounce the use of creatine, which, according to a French medical study, presents a real danger to an athlete's health."Reuse content