Diuretics, or water pills, are medications that help reduce the amount of water in the body. Doctors often prescribe them to treat high blood pressure, which is also known as hypertension.

Diuretics work by triggering the release of more urine and electrolytes, such as sodium and potassium, from the body. High blood pressure means blood pushes too hard on the walls of the blood vessels. This can increase a person’s risk for heart disease and stroke. However, diuretics can reduce blood pressure and the risk of severe health problems.

Read on to learn more about diuretics as a treatment for high blood pressure.

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Diuretics can help reduce blood pressure in people with hypertension. Too much sodium in the bloodstream is a key part of how hypertension develops. Diuretics help remove sodium from the body and support the treatment of high blood pressure.

Diuretics may also help reduce the plasma volume of blood inside vessels. This refers to the total amount of fluid in the blood. Reducing the plasma volume can reduce a person’s risk of serious cardiac events.

Several types of diuretics are available to manage hypertension. Thiazides, loop diuretics, and potassium sparing diuretics (PSDs) all remove water and sodium from the body. However, they all interact with different parts of the kidneys.

These drugs tell the kidneys to expel more sodium. Water binds to the sodium, reducing the blood volume and blood pressure in the process.

A physician can recommend the most appropriate diuretic depending on a person’s overall physical health and other medications in their hypertension management plan.


Thiazides are a common first-line treatment for high blood pressure. They decrease how much sodium the body reabsorbs and increase how much water and sodium the kidneys expel in the urine.

A doctor may prescribe only thiazides or recommend them along with other medications. Two thiazides are common in high blood pressure treatment: metolazone and hydrochlorothiazide.

Some drugs mimic thiazides more effectively but at a lower cost. These are known as thiazide-like diuretics, and one has shown particularly effective results in research. Some evidence suggests that chlorthalidone is more effective than thiazides in reducing blood pressure, takes effect more quickly than thiazides after a dose, and reduces the risk of mortality more than thiazides.

The American Heart Association (AHA) recommends thiazide-like diuretics alongside other blood pressure medications and lifestyle adjustments.

Loop diuretics

Loop diuretics are not a first-line treatment for hypertension. They do not have as potent an effect as thiazides or thiazide-like diuretics on blood pressure.

However, loop diuretics can be helpful for managing hypertension in patients who have specific types of heart failure called heart failure preserved ejection fraction (HFpEF) and heart failure with reduced ejection fraction (HFrEF). One symptom of heart failure is fluid buildup in the limbs, especially the legs.

Potassium-sparing diuretics (PSDs)

Other diuretics are highly effective, but a side effect can be low levels of potassium, a vital electrolyte, in the blood. PSDs help the body get rid of excess water and reduce blood pressure while limiting the amount of potassium that the body gets rid of in the urine.

However, PSDs are not as potent as other diuretics, and doctors do not recommend them as a first-line treatment for hypertension. Examples of PSDs include:

  • triamterene (Dyrenium)
  • amiloride (Midamor)
  • spironolactone (Aldactone)

People taking PSDs need ongoing monitoring to check for high potassium levels, also known as hyperkalemia.

The most common side effect of diuretics is low body fluid levels, or hypovolemia. This can lead to short periods of thirst and dehydration. Severe hypovolemia can develop if a person takes too high a dose of diuretics, which can lead to low blood pressure, dizziness, and fainting.

Other adverse effects of diuretics include:

  • headaches
  • frequent bathroom visits to pee
  • restlessness
  • weakness
  • extreme tiredness
  • sleepiness

Diuretics can also affect levels of electrolytes. For example, thiazides and loop diuretics can lead to low potassium, but PSDs can lead to high potassium.

Loop diuretics and PSDs can also cause:

  • nausea
  • vomiting
  • diarrhea
  • constipation
  • belly pain
  • anorexia

People using diuretics who have low potassium can take a potassium supplement to make sure they have enough. A doctor will monitor electrolyte levels to make sure they stay in a healthy range and adjust the medicine schedule if necessary.

Some studies have looked at the diuretic potential of certain foods and supplements. A 2016 review summed up some promising options. However, the studies included usually did not involve humans or were not large enough to apply the results more widely. These options may include:

  • black cumin
  • coriander
  • hawthorns
  • hibiscus

If a doctor prescribes a particular diuretic, it is important not to swap it out for unproven natural options.

Read on to learn more about natural diuretics.

People with raised blood pressure but a low risk of other health problems can put lifestyle measures in place to help bring down their blood pressure.

These can include:

  • reducing salt intake to under 6 grams (g) a day, ideally moving toward a limit of about 1.5 g per day
  • eating a low-fat diet with good amounts of fruits and vegetables
  • exercising regularly
  • reducing alcohol intake
  • maintaining a moderate body weight
  • consuming less caffeine
  • avoiding or quitting smoking

If a person has consistently high blood pressure that does not respond to lifestyle changes, a doctor may prescribe medication. Diuretics are one of several medications that can help people reduce blood pressure. Other options include:

Diuretics remove water and salt from the body, which can slow blood flow and reduce blood pressure. The three types — thiazides, loop diuretics, and potassium-sparing diuretics — have different purposes when treating high blood pressure.

These can cause side effects, including imbalanced electrolyte levels. A doctor may prescribe potassium supplements to bring a person’s potassium levels up or PSDs for people with hypertension to leave potassium in the body.

There are many ways to manage hypertension before a physician will prescribe diuretics and other medications. These include lifestyle changes, such as a low fat diet, smoking cessation, and more exercise. However, people can take diuretics with other drugs to bring down persistently high blood pressure.