Laxative
Lactulose
Syrup
Quick Summary
Lactulose draws water into the bowel to soften stools.
Constipation
Hepatic encephalopathy
Medical Uses
Constipation: Including in pregnancy and children.
Hepatic encephalopathy: In liver disease.
How it's taken
Take as directed; it may take two to three days to work. Drink plenty of fluids.
Your doctor decides the right dose for you and how long to take it.
Your doctor decides the right dose for you. Follow their instructions and the label.
Common Side Effects
Wind and bloating
Common at first.
Tummy cramps
Sometimes.
Diarrhoea
If too much is taken.
Interactions
Few interactions
Generally safe.
Critical Warnings
Diabetes
Contains some sugars; check with your doctor.
Long-term use
Discuss with your doctor.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- Lactulose: drug information(opens in a new tab) · MedlinePlus, US National Library of Medicine
- Lactulose: a laxative medicine to treat constipation(opens in a new tab) · NHS