What are diuretics?

Diuretics are banned in sports because they can help with weight loss and could be used to speed up the elimination of drugs from the system.

They increase the volume of urine produced by promoting the excretion of salts and water from the kidney. The main classes work by inhibiting the reabsorption of salts and water from the kidney into the bloodstream.

Dr Mark Batt, a consultant in sports medicine at Queens Medical Centre in Nottingham, said diuretics were most frequently prescribed to treat conditions such as heart failure or high blood pressure.

"They are on the banned list because they could be abused by people who are trying to lose weight," he said. "If you lose body water, you lose weight."

This process could be of use for sports where competitors need to meet a certain weight to compete, such as racing, wrestling, boxing or rowing.

"The second reason they are banned is, if you take a banned substance that is excreted through urine, it could speed up the elimination of drugs from the system," said Batt. He added that diuretics themselves were not performance-enhancing substances and it was not healthy to take them unnecessarily.

The potential known side-effects of taking diuretics include dehydration and potassium deficiency.