Diuretics

Diuretics, sometimes called "water pills", help rid the body of salt (sodium) and water and inhibit the re-absorption of water in the kidney; by moving more sodium and water into the urine they reduce the amount of fluid in the blood vessels and so lower blood pressure. In sport they are misused in two ways: as a masking agent to prevent the detection of another banned substance, and to lose weight quickly so an athlete can qualify in a particular weight category.

How the masking effect works

A diuretic's "masking" ability comes from simple dilution: by sharply increasing urine volume and flow rate, it lowers the concentration of any other banned substance (or its metabolites) present in the sample, sometimes enough to push a result below a testing laboratory's detection threshold. This is exactly why anti-doping bodies treat diuretics as seriously as the substances they might be hiding, rather than as a minor drug class on its own.

Why athletes misuse them

Combat-sport and weight-category athletes (such as wrestlers, boxers and judo competitors) are the group most tempted to misuse diuretics, because shedding water weight rapidly before an official weigh-in lets them compete in a lighter category while regaining the lost fluid before the actual contest. Others misuse them simply to look leaner for appearance-based or weight-sensitive sports.

Detection and WADA status …