Written by Mary Ellen Ellis
Medically Reviewed by George Krucik, MD, MBA on May 22, 2013


Diuretics, also called water pills, belong to a class of medications that are designed to increase the loss of water and salt from the body. This is done in different ways depending on the drug. There are a few different types of disorders that are treated with diuretics. They include high blood pressure, heart failure, diabetes, edema, and some types of liver and kidney disease.

There are three different kinds of diuretics that your doctor might prescribe for you. They are called thiazide, loop, and potassium-sparing diuretics. Diuretics are generally safe to take, but there are some possible side effects and interactions with other drugs that can occur.

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Purpose of Using Diuretics

Your doctor may prescribe you diuretics to get rid of excess fluids in your body. There are several different medical conditions that can cause your body to build up too much fluid. You may also take diuretics to treat high blood pressure. By reducing the amount of fluid in your blood vessels, your blood pressure decreases.

Of those conditions in which excess fluids build up in your body, congestive heart failure (CHF) is the one most commonly treated with diuretics. If you have CHF, your heart is not circulating blood effectively and this results in a buildup of fluids throughout your body, also known as edema.

Other, more rare conditions can cause an excess of fluids and be treated with diuretics. These include edema caused by reasons other than CHF, such as diabetes, and certain types of kidney and liver disease.

Types of Diuretics

There are three different types of diuretic medications. They all increase the excretion of fluids from your body, but each does so in a different way. The most commonly prescribed type of diuretic is called thiazide.

Thiazide Diuretics

Thiazides are most commonly used to treat high blood pressure. This is because, in addition to decreasing retained fluids, they also cause your blood vessels to widen. Examples of thiazides include chlorothiazide, hydrochlorothiazide, metolazone, and indapamide.

Loop Diuretics

Loop diuretics remove excess fluid by causing your kidneys to make more urine. This results in the removal of water and salts. Loop diuretics include torsemide, furosemide, bumetanide, and ethacrynic acid. 

Potassium-Sparing Diuretics

Potassium-sparing diuretics, like amiloride, spironolactone, triamterene, and eplerenone, cause your body to get rid of excess fluids. They do this without causing you to lose potassium, an important nutrient. The other diuretics do cause you to lose potassium, which can cause health problems in some people. Potassium-sparing diuretics do not reduce blood pressure as well as the other types, so you may be prescribed this type in combination with another drug.

Risks Associated with Diuretics

Diuretics are generally safe, but there are some risks if you have other medical conditions or if you are taking certain other medications. Before you take a prescribed diuretic, make sure you tell your doctor if you have any of the following conditions or issues:

  • diabetes
  • pancreatitis
  • lupus
  • gout
  • menstrual problems
  • kidney problems
  • frequent dehydration

Any time you begin a new medication, you should tell your doctor all of the other drugs, supplements, or herbs that you are taking. Certain medications, in particular, may interact negatively with diuretics:

  • cyclosporine
  • antidepressants
  • lithium
  • digitalis or digoxin
  • other drugs for high blood pressure

Side Effects of Diuretics

Diuretics are safe for most people to take, but there are some possible side effects. The most common is increased urination, especially with loop diuretics. In rare cases diuretics may cause impotence or an irregular heartbeat. Some common side effects include (Mayo Clinic, 2010):

  • too much or too little potassium in the blood
  • low sodium
  • headache
  • dizziness
  • thirst
  • increased blood sugar
  • muscle cramps
  • increased cholesterol
  • skin rash
  • joint pain (gout)
  • diarrhea
  • increased light sensitivity

If you experience side effects when taking diuretics, speak with your doctor. The common side effect of increased urination usually subsides after a few weeks on the medication, but others may persist. Together with your doctor you can try different medications until you find one or a combination that works best for you and minimizes side effects. Regardless of the side effects, do not stop taking your medication without first speaking to your doctor.

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