Difference Between Laxative and Diuretic

The key difference between laxative and diuretic is that laxatives are substances that induce bowel movements or loosen stools while diuretics are substances that promote the production of urine.

Laxatives and diuretics are two types of medications that induce excretory functions in the body. However, there are several differences between laxatives and diuretics.


1. Overview and Key Difference
2. What is a Laxative 
3. What is a Diuretic
4. Side by Side Comparison – Laxative vs Diuretic in Tabular Form
5. Summary

What is a Laxative?

Laxatives are also known as purgatives or aperients. They can be food or medication consumed either to induce bowel movements or to loosen the stools. Laxatives are generally taken when a person is suffering from constipation. A sufficiently high dose of laxatives may cause diarrhoea.

Types of Laxatives

  1. Bulk-producing agents

These are also known as bulk foaming agents, roughages, and bulking agents. They affect the small and large intestine and make stool bulkier and retain more water. Ex- Metamucil (psyllium husk), Citrucel (methylcellulose), dietary fiber, broccoli, apples and polycarbophil

  1. Stool-softeners (surfactants)

Stool-softeners are anionic substances that also work on large and small intestines and generally take 12 to 72 hours. It enables the penetration of fats and water to stools in order to facilitate easy movement through the digestive system. Prolonged use may reduce effectivity; hence, this is recommended for occasional consumption.

Ex- Colace, Dicto

  1. Lubricants (emollients)

These work on colon and the working period ranges from 6 to 8 hours. It makes stool slippery in order to move down easily and faster.

Ex- Mineral oil

  1. Hydrating Agents

Hydrating agents cause intestine hydrating. Thus it makes softening the stool. It retains water inside the hollows of the intestine and intestinal lumen. It also increases intraluminal pressure.

Two types of hydrating agents can be found

a) Saline laxatives

Site of action – small and large intestine

Onset of action – 30 minutes to 6 hours

Ex – Dibasic sodium phosphate, milk of magnesia, Epsom salt, Magnesium citrate

b) Hyperosmotic agents

It affects the colon and takes 30 minutes to 3 hours to work. It increases bowel movement by drawing water into the bowel from surrounding body tissues.

Ex- Glycerin supporters, Sobrbitol, Lactulose

  1. Stimulants

It stimulates the wave of contractions that pass along the colon propelling the stools along.

Ex- Caascara, pholphthalein, Dulcolax, Senna, Aloin

  1. Miscellaneous

Ex- Castor oil

Laxatives reduce acute and chronic constipation, bowel preparation and chronic immobility.

What is a Diuretic?

Diuretics, also known as water pills, are substances that promote the production of urine. It increases the excretion of water from the body.

Types of Diuretic

  1. High ceiling/loop diurectic

It causes substantial dieresis up to 20% filtered salt and water.  Some loop diuretics inhibit the body’s ability to reabsorb sodium at the ascending loop in the nephron which causes the excretion of water to urine.

Ex- Furosemide, Ethacrynic acid, and Torsemide

  1. Thiazides

They act on distal convoluted tubule and inhibit the sodium-chloride symporter to retain water in the urine

Ex – hydrochlorothiazide,

  1. Carbonic anhydrase inhibitors

It inhibits enzyme carbonic anhydrase which is found in the proximal convoluted tubules.

Ex- Acetazolamide, Methazolamide

  1. Potassium-sparing diuretics

This does not promote the secretion of Potassium into the urine.

There are two specific classes of these diuretics:

Aldoterone antagonistis Ex – spironolactone

Epithelial sodium channel blockers Ex – amiloride and triamterene

  1. Calcium – sparing diuretics

It is used to identify agents that result in a relatively low rate of excretion of Calcium

  1. Osmotic diuretics

They are substances that can increase osmolarity.

Ex- Glucose, Manitol

  1. Low ceiling diuretics

Low ceiling diuretics refers to a pharmacological profile, not a chemical structure.

Use of Diuretic

Diuretics are used to treat

  1. high blood pressure
  2. heart failure
  3. liver failure
  4. edema
  5. kidney stones

Side Effects of Diuretic

Diuretics are generally considered to be safe, but sometimes they can cause increased urination and mineral loss.

What is the Difference Between Laxative and Diuretic?

Laxative loosens the stools while diuretics increase urine excretion. This is the key difference between laxative and diuretic. Moreover, laxatives act on the digestive tract, while diuretics act on kidneys.  In addition, laxatives do not reduce the pressure exerted on blood vessels, while diuretics reduce the pressure exerted on blood vessels by removing excess water.

Summary – Laxative vs Diuretic

The key difference between laxative and diuretic is that laxatives are substances that induce bowel movements or loosen stools while diuretics are substances that promote the production of urine.


1. “What You Need to Know about Water Pills (Diuretics).” Mayo Clinic, Mayo Foundation for Medical Education and Research, Available here.
2. Cunha, John P. “Laxative Types for Constipation Relief, Weight Loss & Side Effects.” MedicineNet, Available here.

Image Courtesy:

1. “Digestive system diagram en” By Mariana Ruiz Villarreal(LadyofHats) – Own work (Public Domain) via Commons Wikimedia
2. “Renal Diuretics” By Haisook at English Wikipedia (CC BY-SA 3.0) via Commons Wikimedia