The side effects can be paranoia, late-night sweats and spiralling legal fees, the consequences potentially career-ending.
For a professional tennis player, taking a drink after a match is no longer a straightforward matter.
In their eagerness to eradicate doping from the sport, the game's authorities have created an atmosphere in which slaking one's thirst without first checking the ingredients is too risky to even contemplate.
Ingest a banned substance once, and you do not play for two years. Do it twice, and you are banned for life.
Argentina's Mariano Puerta, this year's French Open finalist, faces the latter prospect if it is proved he did, as French newspaper L'Equipe alleged on Wednesday, test positive at Roland Garros.
Puerta, who was banned for nine months under an older set of rules for a positive test in 2003, has angrily denounced the report, saying there is no truth in it. He is consulting his lawyers.
He is also living in fear of his next drink.
"After the (previous) positive I've got to be very careful, I can't even take an orange juice," he said on Wednesday.
The day before the L'Equipe report appeared, the International Tennis Federation trumpeted its latest step towards unifying dope testing in the sport with the announcement that it will be responsible for all testing in men's tennis.
It now enforces testing at the Grand Slams, the Davis Cup and the Fed Cup and on the men's ATP Tour. Only women's tour events, excluding Grand Slams, are outside their control.
As ATP chairman Etienne de Villiers observed, a unified approach is a "logical step" in the fight against doping.
In fact the ATP could hardly have resisted. Last year Briton Greg Rusedski escaped punishment for a positive test when he proved it could have been caused by the supplements supplied to the players by the ATP itself.
FLIP SIDE
The ever-tighter drugs policy, however, has a serious flip side for the innocent majority, a point made vividly by 58-times Grand Slam winner Martina Navratilova at Wimbledon this year.
"It's not catching the cheats and the people who are not cheating are so paranoid about it that they can't take care of their body as much as they should," she wrote in her Guardian newspaper column in July.
"Vitamin supplements, energy bars, protein powders, electrolyte replacement drinks, anything: you're afraid of it all.
"I drank someone else's Evian water bottle by accident in Melbourne this year thinking it was mine. I had a couple of sips and it tasted sweet.
"I thought, 'Crap, whose bottle was this and what's in it?' All I could do was keep the bottle and hope all was OK. If I'd tested positive, I would have been banned."
With the science of drug cheating advancing all the time, though, tennis has little option.
"If there were to be many doping cases in tennis, as happened in cycling in 1998, our sport would be in trouble," French player Arnaud Clement told Reuters on Wednesday.
"It could cause problems with sponsors who might decide to invest in a cleaner sport instead."
(Additional reporting by Eric Salliot in France)
