Hydrochlorothiazide, a \'water pill,\' is used to treat high blood pressure and fluid retention caused by various conditions, including heart disease. It causes the kidneys to get rid of unneeded water and salt from the body into the urine. Hydrochlorothiazide may also be used to treat patients with diabetes insipidus and certain electrolyte disturbances and to prevent kidney stones in patients with high levels of calcium in their blood. The diuretic is abbreviated HCTZ, HCT, or HZT. It is also sold as Aquazide H and HydroDIURIL, among other brand names. According to an article written by Reuters, Hydrochlorothiazide is the world\'s most popular blood pressure medicine. In 2008 alone, American doctors wrote 134 million prescriptions for the drug, landing it far ahead of the beta-blocker atenolol, the second-most commonly used blood pressure medicine. Sources: National Center for Biotechnology Information (http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0000714/) Drugs.com (http://www.drugs.com/hydrochlorothiazide.html) Wikipedia ((http://en.wikipedia.org/wiki/Hydrochlorothiazide) Reuters (http://www.reuters.com/article/2011/01/24/us-blood-pressure-idUSTRE70N71E20110124)