At a glance
Laxatives are among the most commonly discussed aspects of managing colorectal conditions. Whether you are dealing with an anal fissure, recovering from surgery, or managing chronic constipation, understanding what different laxatives do helps you make more informed choices.
This guide explains the main types — bulk-forming, osmotic, stimulant, and stool softeners — in plain language. It covers what each type does, when it is commonly used, and what to be aware of.
The main types
Bulk-forming laxatives
What they do: add fibre and bulk to the stool, which stimulates the bowel to move. They work by absorbing water in the intestine, making the stool larger and softer.
Common examples: psyllium husk (Fybogel), ispaghula husk, methylcellulose
How to take them: with plenty of water. This is critical — without adequate fluid, bulk-forming laxatives can actually make constipation worse.
How long they take: one to three days to reach full effect. They work best when taken consistently rather than as a one-off.
When they are commonly used:
- As a first-line approach for chronic constipation
- To maintain soft, formed stools with anal fissures or hemorrhoids
- As a fibre supplement when dietary fibre is insufficient
What to know:
- Start with a low dose and increase gradually to reduce bloating and gas
- Must be taken with plenty of water — at least a full glass
- Not suitable if you have a bowel obstruction
- Can cause bloating initially, which usually settles
Osmotic laxatives
What they do: draw water into the bowel from the surrounding tissue, making the stool softer and easier to pass.
Common examples: Movicol (macrogol), lactulose, polyethylene glycol (PEG)
How to take them: dissolved in water (for sachets) or as a liquid
How long they take: one to three days for full effect, though some people notice results within hours
When they are commonly used:
- For chronic constipation
- Before and after colorectal surgery to keep stools soft
- When bulk-forming laxatives alone are not sufficient
- For faecal impaction (at higher doses under medical supervision)
What to know:
- Generally considered safe for longer-term use
- Can cause bloating and cramping, especially initially
- Lactulose may cause more gas and bloating than macrogol
- Macrogol-based products (like Movicol) are widely used in colorectal care
Stimulant laxatives
What they do: stimulate the nerves in the bowel wall, causing the muscles to contract and move stool through more quickly.
Common examples: senna, bisacodyl (Dulcolax), sodium picosulfate
How to take them: usually as tablets, sometimes as suppositories
How long they take: six to twelve hours when taken orally. Suppository forms work faster — typically within an hour.
When they are commonly used:
- For short-term relief of constipation
- When gentler laxatives have not been effective
- Sometimes used before medical procedures
What to know:
- Generally recommended for short-term use
- Can cause cramping and urgency
- Long-term use may affect the bowel’s ability to function independently — discuss with a clinician
- The urgency they produce can be problematic for people with fissures or recent surgery
Stool softeners
What they do: soften the stool by drawing water into it, making it easier to pass without straining.
Common examples: docusate sodium
How to take them: usually as capsules
How long they take: one to three days
When they are commonly used:
- When soft stools are the primary goal (e.g., with fissures, after surgery)
- When straining needs to be avoided
- As a gentler alternative to other laxative types
What to know:
- The gentlest option but also the mildest in effect
- Often used in combination with other approaches
- Safe for most people, but check with a pharmacist if you take other medications
Choosing the right type
The right laxative depends on the situation:
| Situation | Commonly used type |
|---|---|
| Anal fissure — keeping stools soft | Osmotic + stool softener |
| Post-surgical recovery | Osmotic laxative, started before surgery |
| Chronic constipation | Bulk-forming as first line, osmotic if needed |
| Acute constipation needing quick relief | Stimulant (short-term) |
| Fibre intake too low | Bulk-forming laxative or fibre supplement |
Many people use a combination — for example, a bulk-forming laxative for ongoing fibre alongside an osmotic laxative for stool softening during recovery.
What to be careful about
- Stimulant laxatives are for short-term use unless your clinician advises otherwise
- Drink plenty of water with all laxatives, especially bulk-forming types
- Start any new laxative at a low dose and increase gradually
- Do not use laxatives to manage weight — this is dangerous and ineffective
- Talk to a pharmacist or clinician if you are unsure which type is appropriate, or if you take other medications
When laxatives are not enough
If constipation persists despite laxative use, or if you are using laxatives regularly without improvement, that is a signal to discuss further with a clinician. Persistent constipation can have underlying causes that benefit from investigation.