Laxatives explained: which type does what?

First: lifestyle before laxatives

The NHS says that for most adults with constipation, it’s usually recommended to try lifestyle changes first: more fiber, more fluids, more movement and a better toilet routine. Our constipation guide covers those.

The 4 main types

Type	Examples (NHS)	How it works	How long it takes
Bulk-forming	Fybogel (ispaghula husk)	Adds fiber to poo, making it bigger and softer so bowel muscles push it out	Up to 3 days
Osmotic	Lactulose, macrogol	Draws more water into the bowel so poo is softer	2 to 3 days
Stool softeners	Arachis oil, docusate	Lets more water and fat into poo so it’s softer and more slippery	12 hours to 3 days
Stimulant	Bisacodyl, senna	Triggers bowel muscles to push poo out	6 to 12 hours

Not every laxative is listed here. Check the leaflet or ask a pharmacist.

Which one to try first?

The NHS says if you’re buying without a prescription, it’s usually best to try a bulk-forming laxative first. If that doesn’t work, or you’re not sure, a pharmacist can help. The NHS adds: try not to be embarrassed, they’re used to these conversations.

How to use them safely

From the NHS:

• if you take bulk-forming or osmotic laxatives, drink plenty of fluids to avoid dehydration
• some need to be taken at a certain time of day, so read the leaflet
• if you bought them without a prescription, stop when your constipation improves and don’t take them for longer than 7 days
• if you’ve used them for 3 days and they haven’t helped, speak to a doctor or pharmacist

Common side effects include farting, bloating, stomach pain and cramps, feeling or being sick, and diarrhea. These usually stop when you stop the laxative. Using laxatives too often or for too long can cause problems like dehydration.

When laxatives are used for other reasons

The NHS says laxatives can also help if you have a condition like an anal fissure, where soft poo makes going less painful, or if a medicine you take tends to cause constipation. Those uses are guided by your doctor or pharmacist.

Keep track

Mon 21:00  Paper note: started bulk-forming laxative, extra water
Tue  (no poop logged)
Wed 08:30  Poop: type 3
Thu 08:15  Poop: type 4
Thu  Paper note: stopped laxative, feeling normal

Logging the start and stop dates as text alongside your meals means you and your pharmacist can see exactly what happened. PoopAI’s weekly report shows how your Bristol types moved.

When to see a GP

The NHS says see a GP if constipation isn’t getting better with treatment, keeps happening, or comes with blood in your poo, weight loss, tiredness or tummy pain. Speak to a GP before stopping any prescribed medicine.

Questions to ask yourself

Before buying a laxative, a few honest answers help a pharmacist pick the right one. How long have you been constipated? Have you tried more fiber, fluids and activity yet? Are you taking any medicines, which can sometimes cause constipation? Are you pregnant or breastfeeding? Have you used laxatives often in the past? Write the answers down, plus your recent Bristol types. If you do start one, keep logging so you can see when things change and stop when you no longer need it. If you’re still needing laxatives after a short while, check in with your GP.

Wrap-up

Four types, four speeds. Start with lifestyle, then a bulk-forming laxative with plenty of water, and ask a pharmacist if you’re unsure. If you need them for more than a week, it’s time to see a GP.