Lactulose
About
Lactulose is a laxative taken to treat constipation (difficulty pooing). It's also taken to help a condition caused by severe liver disease called hepatic encephalopathy. Lactulose comes as a sweet syrup that you swallow. It's available on prescription and to buy from pharmacies. Lactulose relieves constipation by drawing water into your bowel to make poo softer. The most common side effects are diarrhoea, bloating and wind. These are usually mild and do not last long. Lactulose takes at least 2 days to work. Talk to your doctor if your constipation has not improved after 4 or 5 days. If you find the taste of lactulose too sweet, you can dilute it with fruit juice or water. Page last reviewed: 4 March 2022 Next review due: 4 March 2025
Key facts
Lactulose relieves constipation by drawing water into your bowel to make poo softer.
The most common side effects are diarrhoea, bloating and wind. These are usually mild and do not last long.
Lactulose takes at least 2 days to work. Talk to your doctor if your constipation has not improved after 4 or 5 days.
If you find the taste of lactulose too sweet, you can dilute it with fruit juice or water.