Lactulose
Also known as: Duphalac
What it's for
Lactulose is a gentle laxative for constipation. It works by drawing water into the bowel to soften your stool. It is safe for long-term use if needed.
Comes as: Liquid
How to take it
- Adults: Usually 15ml to 45ml twice daily to start.
- Reduce dose once bowels are regular.
- May take 2 or 3 days to work.
- Can be taken with water or fruit juice.
Doses here are typical. Always follow the instructions from your prescriber or on the packet — they come first.
Common side effects
- Wind and bloating (common at first)
- Stomach cramps
- Feeling sick
The leaflet inside the packet lists all known side effects.
Important safety points
- May take 2 to 3 days to start working
- Can cause wind and bloating initially - usually settles
- Drink plenty of fluids
- Tell your doctor if you have diabetes (contains sugars)
Get medical help urgently if…
- You have severe stomach pain
- You have been constipated for more than a week despite treatment
- You notice blood when you go to the toilet
- You have vomiting with constipation
Call NHS 111 for urgent advice, or 999 if someone is seriously unwell.
Before you act on anything here
This page is general information, written to help you understand — it is not personal medical advice and it cannot tell you what is right for you. Talk to your own GP, pharmacist or nurse about your own health.
- Need help now but it's not an emergency? Call NHS 111 or use 111.nhs.uk.
- Emergency? Call 999 or go to A&E.