Hydrochlorothiazide (HCTZ) or Hydrodiuril is a diuretic that helps your body to loose water weight. HCTZ works by preventing the absorption of salt, which causes the retention of water, into your. For athletes and bodybuilder controlling your water weight is important if you are trying to meet certain weigh guidelines. HCTZ also helps give a leaner look before a bodybuilding show. Generally people will take between 25mg-200mg per day for several days.