Actions and uses
Diuretics stimulate the kidneys to remove more water and salt (sodium) from the body. Diuretics may also slightly dilate or widen blood vessels. Diuretics help rid the body of extra fluid and sodium. They increase urination, decrease swelling in the legs, decrease breathlessness, and lower blood pressure. They also reduce the risk of complications caused by high blood pressure.
Dosage often starts low and is increased as needed to reduce fluid buildup and prevent side effects. Diuretics can be taken 2 to 3 times per week, every other day, once a day, or several times daily. They are most often taken by mouth, but some can be injected into a vein if you are in the hospital.

Side effects and adverse effects
It may take some time to determine the correct dose and the best time of day to take the drug, depending on your age, body size, kidney function, amount of fluid buildup, and dietary sodium intake. General side effects include urinating more often while taking a diuretic. Timing of the dosage can often be adjusted so that the increased urination doesn't occur at inconvenient times. The loss of fluid also leads to increased thirst so it is important to have plenty of fluid intake while taking a diuretic. High doses of these drugs can cause dehydration or low blood pressure. Older adults may be more prone to heat exhaustion if they are taking one or more diuretics. Diuretics can also cause potassium loss, which may lead to an abnormal heartbeat. These drugs can cause changes in sugar and uric acid.

Nursing Implications
Weigh patient daily to monitor water loss and determine if doses of medication need to be adjusted. Take frequent blood tests to check potassium levels while patient is on a diuretic.
If the diuretics flush too much fluid and salt from the body, they may have a kidney problem. Diuretics may interact with nonsteroidal anti-inflammatory drugs (NSAIDs).

Heart Failure Society of America (2006). HFSA 2006 comprehensive heart failure practice guidelines: Executive summary. Journal of Cardiac Failure, 12(1): 10–38. Also available online: http://www.abouthf.org/guidelines.htm.