Digestive health · Osmotic laxative
Lactulose
Lactulose is a gentle osmotic laxative used for occasional or long-term constipation.
OTCKidney warningLiver warningPaediatric useSenior precautionOverview & typical uses
Lactulose is a gentle osmotic laxative used for occasional or long-term constipation.
Primary uses
- Occasional or chronic constipation
- Hepatic encephalopathy (under clinical supervision)
How it works
Draws water into the bowel, softens stool, and increases the frequency of bowel movements. Effect usually appears in 24 to 48 hours.
Available forms & strengths
- Oral solution — 10 g / 15 mL (Oral)
- Powder sachet — 10 g (Oral)
General precautions & contraindications
Do not use if
- Bowel obstruction
- Known galactosaemia
Pregnancy
Generally considered safe. Poorly absorbed; considered safe in pregnancy.
Breastfeeding
Generally considered safe. Poorly absorbed; safe during breastfeeding.
Kidney considerations
- No dose adjustment needed for routine use.
Liver considerations
- Used therapeutically in some liver conditions — follow clinician guidance for hepatic encephalopathy.
Paediatric use
Under clinical supervision.
Older adults
Well tolerated for long-term constipation management.
Common side effects
- Bloating and gas (usually settles within a few days)
- Abdominal cramps
- Diarrhoea if too much is taken
Serious warnings — seek help if these appear
- Electrolyte imbalance with excessive use
- Serious allergic reaction (very rare)
Drug interactions
Additive effect — combine only if advised.
Food & alcohol precautions
Drink plenty of water alongside lactulose for best effect.
Storage, missed dose & overdose
Storage
Store below 25 °C, out of reach of children.
If a dose is missed
Take when remembered unless close to the next dose.
Overdose
Overdose causes diarrhoea and dehydration. Increase fluids and seek advice if severe.
Frequently asked questions
Usually 24 to 48 hours. Give it time before increasing the amount.
Medical references
- British National Formulary — Lactulose — BNF (NICE)
- WHO Model Formulary — World Health Organization
Content last reviewed: 2025-01-01
Medical disclaimer
This information is for educational purposes only and should not replace professional medical advice. Please consult a licensed pharmacist or clinician for advice tailored to your personal circumstances.