Hydrochlorothiazide is a type of medication known as a diuretic. Diuretics are banned in sports because they can be used for rapid weight loss and to mask other prohibited drugs. The primary use of Hydrochlorothiazide is to reduce blood pressure. As an athlete, you can apply for an exemption to use Hydrochlorothiazide, with the support of your doctor, if you need Hydrochlorothiazide to treat high blood pressure.