Diuretics, commonly known as water pills, are an effective and inexpensive drug used for treating high blood pressure or hypertension. They generally work by stimulating the kidneys to remove more water and salt from the body. As a result, you tend to urinate more after taking these medications. This leads to a decrease in plasma volume, thus lowering the liquid volume in the arteries and reducing overall blood pressure. The next sections will provide you more facts about the subtypes and effects of diuretics in treating hypertension. 
Thiazide diuretics are often the first line of treatment for hypertension. You can use them alone or in combination with other medications. There are two subtypes of thiazides, including hydrochlorothiazide and metolazone. They have a direct effect on the kidneys and promote urine flow. This helps reduce plasma volume and extracellular fluid, which subsequently reduces blood pressure. These mediations also retain calcium while causing potassium loss. Compared to other kinds of diuretics, the diuretic effect of thiazides is quite weak, making it suitable for mild cases of hypertension. Some thiazide-like diuretics, which work like these medications but are less expensive, are also available.