Hydrochlorothiazide is a drug used in the treatment of high blood pressure (hypertension) and swelling. It may also be used in the treatment of diabetes insipidus and renal tubular acidosis. It belongs to the thiazide class of diuretics, drugs which reduce blood volume by increasing urination.Hydrochlorothiazide is a water pill (diuretic) medication which is used to treat high blood pressure. It is also used to treat diabetes insipidus, renal tubular acidosis and reduce the risk of kidney stones. Also, Hydrochlorothiazide is used to reduce extra fluid in the body, hence, reduce symptoms such as shortness of breath or swelling in your feet or ankles. Hydrochlorothiazide works by reducing blood volumes on the kidneys to reduce sodium reabsorption in the distal convoluted tubule. Hydrochlorothiazide is usually recommended once in the morning and is taken by mouth. It is encouraged not to take this medication within 4 hours of your bedtime having to get up to urinate. Hydrochlorothiazide adverse effects may include; low blood levels of potassium, high levels of uric acid in the blood, high blood sugar, hyperlipidemia, headache, nausea, photosensitivity, weight gain, pancreatitis and gout among others. Inform your doctor if you have any allergies before taking Hydrochlorothiazide because it may contain inactive ingredients which may cause other problems or allergic reactions.