How do laxatives actually work?

Laxatives are often the first line of treatment for constipation.

Laxatives work in a number of different ways, all with the goal assisting the bowel to empty its contents. There are a number of ways this can occur, and it pays to think through which laxative option is best for you, based on the timing of the likely bowel movement, the urgency with which you need relief, and any other health considerations. It’s important to remember that everyone’s bodies are different, and while one person may reliably empty their bowels each day, others will do so every 2-3 days.

Bulking agents

By providing supplementary fibre to the diet, bulking agents add bulk to the stool, as well as absorbing water. This has the combined effect of adding weight to the stool, while ensuring it maintains lubricated. It’s important to stay well hydrated if you add a bulking agent to your diet, as the fibre bulk without water will cause the stool to dry out, resulting in constipation. A bulking agent isn’t recommended for the treatment of constipation; rather it is better for maintaining regularity. It can be used safely on a regular basis.


Surfactants or ‘stool softeners’ work by drawing fats and water from the digestive system into the stool. This softens the stool, allowing it to move more easily along the large and small intestine. Surfactants become less effective when used regularly, so only reach for this option occasionally.


These lubricants are one of the faster-acting laxatives, which act by adding oil to, and subsequently lubricating the stool. Emollients should only be used occasionally and their over-use can cause difficulties in absorbing some vitamins and minerals.


Also known as irritants or contact laxatives, these laxatives are different in that they stimulate the peristaltic action of the intestine. This ‘wave’ of contractions in the intestine forces the stool to be expelled. These are not suitable for regular use, and overuse may result in a ‘lazy’ bowel, characterised by reduced natural contractions of the intestine. One example of a stimulant laxative is Dulcolax tablet for constipation.

Osmotic Agents

Osmotic laxatives are usually reserved for when rapid bowel elimination is required, for example, prior to surgical procedures. They are usually saline-based or glycerine-based, and work by drawing water into the intestine, thus softening the stool. Results can be achieved in a matter of hours.

While laxatives are a useful treatment option for when you’re uncomfortable and needing some help to move things along, it’s important not to become reliant on them for your regular bowel movements. Prevention is always better than cure, and this is possible by consuming lots of fresh fruit and vegetables, 2-3 litres of water daily, and maintaining at least a light level of activity daily.

Written by Amelia Stuckey

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