Lactulose

What is lactulose?

Lactulose is a synthetic sugar-based medicine that can be used to treat constipation. It may also be used for a liver-related brain condition called hepatic encephalopathy[1].  

Lactulose is an osmotic laxative that is broken down in your bowel to produce substances that draw water into the bowel, making stools softer and easier to pass. This can help with hepatic encephalopathy as it helps the body remove the toxins that build up when the liver is failing[1]. 

What is lactulose used for?

Doctors commonly prescribe lactulose for constipation, where it helps make stools softer and easier to pass. It reduces the production of toxic substances in the intestine and helps the body remove these toxins by its laxative action. It also helps with hepatic encephalopathy – a serious condition caused by liver failure that affects brain function – where it increases excretion of ammonia. This toxin contributes to the confusion and other mental changes that can occur with this condition[1]. 

How does lactulose work?

Once lactulose reaches the colon, it is broken down by gut bacteria into low-molecular-weight organic acids, such as lactic acid and acetic acid. These acids then draw water into the colon, softening stools and promoting bowel movements[1].  

Lactulose also lowers the pH of the colon, converting ammonia (which is absorbable and toxic) into ammonium (which is not). This helps remove excess ammonia from the body[1].  

Who can take lactulose?

Lactulose is generally safe for adults. The dose, though, should be adjusted by your doctor or pharmacist depending on age, weight, and condition[1]. 

For children, it should be used only in exceptional circumstances and under medical supervision because it can influence the normal reflexes for passing stools. Do not give lactulose to children under 14 years old before consulting your doctor or pharmacist for prescription and supervision. 

Pregnant or breastfeeding individuals can usually safely take lactulose, but always consult a doctor or pharmacist first. Those with galactose intolerance, due to the sugar content in lactulose, may not be suitable, along with those following a low-galactose or lactose-free diet. In these cases, alternative treatments may be needed. 

You should not take lactulose if[2]: 

• You are allergic (hypersensitive) to lactulose or any of the other ingredients 

• You have a rare problem called 'galactosaemia' 

• You have a blockage caused by anything else but normal constipation, gastrointestinal perforation or risk of perforation 

• You have a galactose or fructose intolerance 

• You have a lactase deficiency 

• You have glucose-galactose malabsorption 

Do not take lactulose if any of the above apply to you. If you are not sure, talk to your doctor or pharmacist before taking lactulose. 

You should consult with your doctor or pharmacist if you suffer from unexplained tummy ache, if you are unable to digest milk sugar (lactose intolerant), and if you have diabetes. 

Please tell your doctor or pharmacist about any conditions you may have before starting lactulose, and always follow the instructions in the Patient Information Leaflet[2]. 

What is the typical dosage of lactulose?

Dosage depends on the condition being treated. With constipation in adults, the typical starting dose is 15ml once or twice daily.  

When treating hepatic encephalopathy, the common starting dose is 30ml to 45ml, three or four times a day, administered in 6 to 9 5ml spoonfuls. 

 Children may be given different doses depending on age and weight. You should always follow your doctor’s or pharmacist’s guidance[1]. 

How do you take lactulose?

Usually, lactulose is available as a sweet-tasting liquid or as a powder for mixing. You can take it with or without food. It’s important to always measure the dose carefully using a measuring spoon, cup, or oral syringe – not a standard kitchen spoon[1]. 

You can mix lactulose with fruit juice or water. You should drink plenty of fluids, approximately 6 to 8 glasses throughout the day. Swallow the dose immediately. Do not keep it in your mouth as the sugar content may lead to tooth decay, particularly if lactulose is taken for long periods[1]. 

Can you stop taking lactulose suddenly?

If you’re taking lactulose for short-term constipation, you can usually stop once your bowel movements return to normal. However, for hepatic encephalopathy, you should only stop or adjust your dose under medical supervision. Stopping abruptly can cause a serious return of symptoms otherwise. It’s best to get your doctor’s or pharmacist’s advice before stopping any treatment[1]. 

What should you do if you take too much lactulose?

Taking too much lactulose may lead to conditions such as diarrhoea, dehydration, or electrolyte imbalances (low sodium or potassium levels). An electrolyte imbalance is when levels of substances like sodium, potassium and magnesium in your body get too high or too low. A severe electrolyte imbalance can cause serious health problems, like muscle spasms, twitching, a seizure or fit[2].  

You should contact your doctor or pharmacist if taken more than a single extra dose or regardless. In the meantime, drink plenty of fluids to stay hydrated. 

What should you do if you forget a dose of lactulose?

If you forget a dose of lactulose, you can take the missed dose as soon as you remember. If your next dose is due, skip the missed one altogether and continue at the usual time. You should not take two doses at once to make up for a missed dose[1]. 

Which medicines should you avoid while taking lactulose?

You can take lactulose with other medicines or herbal remedies[2]. It’s vital to always inform your doctor or pharmacist about any other medicines or supplements you are taking. 

You’ll usually only take one laxative to ease your symptoms; however, you may need to take two to get your bowels moving. You should only do this on advice of your doctor or pharmacist as it does increase the risk of side effects[1]. 

Always inform your doctor or pharmacist about all medications and supplements you take before you start a new medicine, and follow the instructions in the Patient Information Leaflet[2]. 

What are the side effects of lactulose?

The most common side effects of lactulose include abdominal pain, bloating or increased gas, along with stomach cramps, diarrhoea, vomiting, and nausea. You should seek medical attention if you experience severe or prolonged diarrhoea, or any allergic reactions, such as rash, swelling, or difficulty breathing[1]. 

Flatulence may occur during the first few days of treatment. As a rule, it disappears after a few days. 

If you experience any side effects, including those not listed, you are encouraged to report them via the Yellow Card Scheme or contact your doctor, pharmacist, or nurse. This information is intended as a summary for general awareness and does not replace professional medical advice.

The information provided in the side effects section is not a comprehensive list of all possible side effects associated with this medication. For a complete list of side effects, please refer to the Patient Information Leaflet (PIL) provided with your medication or consult your healthcare professional[2]. 

Frequently asked questions about lactulose

How long does lactulose take to work? 

For constipation, lactulose usually starts working after 48 hours. With hepatic encephalopathy, it may take a bit longer – but should still be effective within a few days. You should talk to your doctor if you have no improvement after 4 or 5 days[1]. 

Can I take lactulose every day? 

Ideally, you’ll only take lactulose occasionally, as you need it, and only for a few days at a time. Using laxatives like lactulose for long periods can lead to long-lasting diarrhoea, and an electrolyte imbalance[2].  

However, there are certain situations where you have to take lactulose for many months, like if you have regular constipation or if you have hepatic encephalopathy. Your doctor or pharmacist will advise what you take and for how long. 

Yes, it is safe to take lactulose daily if your doctor has prescribed it for a chronic condition. However, your dosage should be monitored regularly to avoid side effects. In most cases, you’ll stop using lactulose once constipation symptoms have eased[1]. 

Is lactulose safe during pregnancy? 

Lactulose is generally considered safe in pregnancy. You should always check with your doctor, however, before starting or continuing any treatment[1]. 

Can I drink alcohol while taking lactulose? 

If you’re taking lactulose for hepatic encephalopathy, you should avoid alcohol entirely. In this case, it can make liver-related brain symptoms worse. If you’re taking lactulose for constipation, occasional alcohol use is less of a concern but should still be limited[1]. 

For the official NHS guide to lactulose, visit their website.