Diuretics: Mechanism of Action & Types

Nursing Knowledge

Diuretics: Mechanism of Action & Types

Diuretics are a class of medications that are commonly used in clinical practice. They are indicated for a variety of conditions, including hypertension, heart failure, and edema. As a nurse, it is important to have a thorough understanding of diuretics and the mechanisms of action, as well as potential side effects and interactions with other medications.
Last updated: December 4, 2023

Table of contents

What are diuretics?

Diuretics are medications that increase the kidney’s production and output of urine in an effort to lower blood pressure and/or decrease edema. They’re commonly used to treat conditions like hypertension (high blood pressure), heart failure, and edema (fluid buildup).

What are the types of diuretics? 

Loop diuretics

  • Limit reabsorption of Na+ and Cl, increasing urine production
  • Work in loop of Henle to remove salt and excess water
  • Furosemide is commonly used.


  • Thiazide effects are similar to loop diuretics. They increase renal excretion on Na+, Cl, K+ and H2O and elevate plasma levels of glucose and uric acid.
  • Thiazide is not effective when renal blood flow is low.
  • Thiazide-induced diuresis is less than loop diuretic.
  •  HCTZ is the most commonly prescribed thiazide diuretic.

Potassium-sparing diuretics

  • Potassium-sparing diuretics cause mild increase in urine output.
  • Not often used in monotherapy, but can be used with loop diuretics to counteract K+ loss from other medications.
  • Hyperkalemia is an adverse effect which can lead to life-threatening dysrhythmias.
  • Use spironolactone with caution when taking other medications that also raise K+ (ACE inhibitors, ARBs and DRIs).
  • Removes salt and water without removing excess potassium

Carbonic anhydrase inhibitors

  • Osmotic diuretic given IV
  • Most of filtered drug remains in the nephron
  • Increases osmotic pressure in lumen of the proximal tubule and the loop of Henle
  • Causes increased water diuresis
Nursing cs comparison of diuretics

Comparison chart of diuretics

A comparison of thiazide, loop diuretics, and potassium-sparing diuretics

How do diuretics work?

Mechanism of action of loop diuretics

Loop diuretics (e.g., furosemide) reduce Na+ reabsorption in the loop of Henle.

Mechanism of action of thiazides

Thiazides (e.g., hydrochlorothiazide) inhibit Na+, Mg+, K+, and Cl  reabsorption in the distal convoluted tubules. 

Mechanism of action of potassium-sparing diuretics

Potassium-sparing diuretics (e.g., spironolactone, triamterone) inhibit aldosterone receptors or prevent Na+ reabsorption in the distal tubule. 

What is a nephron? 

A nephron is a functional unit of the kidney. Each kidney has about 1,000,000 nephrons. Nephrons stretch from the cortex to the medulla of the kidney. Each nephron has three parts: 

  • Tubule (PCT & DCT)
  • Glomerulus
  • Bowman’s capsule

What are diuretics used for? 

Table: Indications of different types of diuretics

Thiazide diureticsPotassium-sparing diureticsLoop diuretics
Common drugsHydrochlorothiazideSpironolactoneTriamtereneFurosemide
UsesHypertension,edema, heart failureHypertension, edema, heart failure, acne, hirsutismHypertension, edema, heart failureHypertension, edema, heart failure

Side effects of diuretics: comparison

Table: Side effects of different types of diuretics

Thiazide diureticsPotassium-sparing diureticsLoop diuretics
Common drugsHydrochlorothiazideSpironolactoneTriamtereneFurosemide
Side effectsHypokalemia, hyponatremia, photosensitivityHyperkalemia, lightheadedness, gynecomastiaHypokalemia, hyponatremia, hypomagnesemia 

Nursing teachings for diuretics

  • Take medication as directed.
  • Elderly and fall-risk patients should take any evening doses by early evening.
  • Educate for fluid intake as ordered by provider.
  • Monitor for weight changes.
  • Maintain follow-up visits.

What foods are natural diuretics? 

Many foods and beverages have natural diuretic properties, including:

  • Watermelon
  • Cucumber
  • Lemon
  • Pineapple
  • Ginger
  • Parsley
  • Celery
  • Berries 
  • Beets
  • Green tea
  • Asparagus
  • Coffee (caffeine)
  • Grapes
  • Apple cider vinegar

When to stop diuretics in heart failure 

The decision to discontinue diuretics or adjust the dose for clients with heart failure is made by the supervising physician. 

Considerations influencing the decision to discontinue diuretics can include the following: 

  • If symptoms of fluid overload or congestion stop (clinical stability)
  • Risk of hypotension present
  • Electrolyte imbalances present
  • Decline in kidney function
  • Interactions with other medications 
  • Client’s weight drops significantly 


Diuretics: Mechanism of Action & Types

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Diuretics, also called water pills, are a some of the most commonly prescribed medications out there. Find out how they work and what you should to know about them.

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