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a group of diuretics in the thiazide family; they decrease reabsorption of sodium by the kidney and thereby increase loss of water and sodium. They also increase urinary secretion of chloride, potassium, and, to some extent, bicarbonate ions. These are the most frequently prescribed diuretics because they are moderately potent and have relatively few side effects. Most act within 1 hour after being taken and are excreted in 3 to 6 hours. Patients who are taking a thiazide diuretic should be monitored for electrolyte imbalances, metabolic acidosis, and, in the case of diabetic patients, hyperglycemia, which may necessitate an increase in insulin dosage. Because GI irritation can occur, it is advisable to take these diuretics at mealtime. See also diuretic.