Diuretics, also called water pills, are medications designed to increase the amount of water and salt expelled from the body as urine.

There are three types of prescription diuretics. They’re often prescribed to help treat high blood pressure, but they’re used for other conditions as well.

The most common condition treated with diuretics is high blood pressure. The drugs reduce the amount of fluid in your blood vessels, and this helps lower your blood pressure.

Other conditions are also treated with diuretics. Congestive heart failure, for instance, keeps your heart from pumping blood effectively throughout your body. This leads to a buildup of fluids in your body, which is called edema. Diuretics can help reduce this fluid buildup.

The three types of diuretic medications are called thiazide, loop, and potassium-sparing diuretics. All of them make your body excrete more fluids as urine.

Thiazide diuretics

Thiazides are the most commonly prescribed diuretics. They’re most often used to treat high blood pressure. These drugs not only decrease fluids, they also cause your blood vessels to relax.

Thiazides are sometimes taken with other medications used to lower blood pressure. Examples of thiazides include:

  • chlorthalidone
  • hydrochlorothiazide (Microzide)
  • metolazone
  • indapamide

Loop diuretics

Loop diuretics are often used to treat heart failure. Examples of these drugs include:

  • torsemide (Demadex)
  • furosemide (Lasix)
  • bumetanide

Potassium-sparing diuretics

Potassium-sparing diuretics reduce fluid levels in your body without causing you to lose potassium, an important nutrient.

The other types of diuretics cause you to lose potassium, which can lead to health problems such as arrhythmia. Potassium-sparing diuretics may be prescribed for people at risk of low potassium levels, such as those who take other medications that deplete potassium.

Potassium-sparing diuretics don’t reduce blood pressure as well as the other types of diuretics do. Therefore, your doctor may prescribe a potassium-sparing diuretic with another medication that also lowers blood pressure.

Examples of potassium-sparing diuretics include:

  • amiloride
  • triamterene (Dyrenium)
  • spironolactone (Aldactone)
  • eplerenone (Inspra)

When taken as prescribed, diuretics are generally well tolerated. However, they can still cause some side effects.

More common side effects

The more common side effects of diuretics include:

Serious side effects

In rare cases, diuretics may cause serious side effects. These can include:

What you can do

If you have side effects that bother you while taking diuretics, talk to your doctor. They may prescribe a different medication or combination of medications to help reduce your side effects.

Whether or not you have side effects, don’t stop taking your diuretic without first talking to your doctor.

Diuretics are generally safe, but there are some risks if you have other medical conditions or take certain medications.

Conditions of concern

Before you take a prescribed diuretic, be sure to tell your doctor if you have any of the following conditions or issues:

Drug interactions

When you begin a new medication, make sure to tell your doctor about any other medications, supplements, or herbs you’re taking. Some medications that might interact with a diuretic include:

  • cyclosporine (Restasis)
  • antidepressants such as fluoxetine (Prozac) and venlafaxine (Effexor XR)
  • lithium
  • digoxin (Digox)
  • other drugs for high blood pressure

Some herbs and plants are considered “natural diuretics,” including:

  • hawthorn
  • green and black tea
  • parsley

These substances aren’t meant to be used to replace a prescription diuretic. If you have questions about diuretics and other treatment options, talk to your doctor.

Prescription diuretics can be helpful in treating serious conditions, such as heart failure, to less-pressing conditions, such as mild high blood pressure.

If your doctor prescribes a diuretic, feel free to ask them any questions you may have. Consider discussing these questions:

  • How will I know my diuretic is working the way it’s supposed to work?
  • Am I taking any medications that might interact with a diuretic?
  • Should I follow a low-salt diet while taking a diuretic?
  • Should I have my blood pressure and kidney function tested while taking this drug?
  • Should I take a potassium supplement or avoid foods that contain potassium?

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Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.