How does lactulose work?
Lactulose is a type of laxative called an osmotic laxative.
It is broken down in your bowel into substances that pull water out from your body and into your bowel to soften poo and make it easier to pass.
People with liver disease can sometimes get problems in their brain (hepatic encephalopathy). This happens because the liver is not clearing toxins properly. Lactulose clears the bowels and helps the body remove the toxins that build up when the liver is failing.
When will I feel better?
It takes a couple of days for lactulose to work.
Talk to your doctor if you are still constipated after 3 days.
If you take it for liver disease you may not feel better but it will help prevent you developing some of the symptoms of liver problems.
Are there any long-term side effects?
Ideally, you'll only take lactulose occasionally and for a few days at a time. Using laxatives like lactulose for longer can lead to diarrhoea that lasts a long time, and can cause an electrolyte imbalance. This is where 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, such as:
- muscle spasms
- twitching
- a seizure or fit
But there are some situations where you may need to take lactulose for many months, for instance, if you keep getting constipation or if you have a health problem called hepatic encephalopathy. Your doctor will advise you exactly how long you need to take lactulose for and how much to take.
How does lactulose compare with other laxatives?
There are other types of laxatives. They work in a different way to lactulose but are equally good at treating constipation. Some work more quickly than lactulose.
Bulk-forming laxatives, for example Fybogel and methylcellulose, increase the "bulk" or weight of poo which in turn stimulates bowel movement. They take 2 or 3 days to work. They are normally tried first before trying a laxative like lactulose.
Stimulant laxatives, for example senna and bisacodyl, speed up your bowels by stimulating the nerves that control the muscles lining your gut. They work more quickly than other laxatives. If you take them at bedtime, they work overnight. They are normally tried after a laxative like lactulose has not worked.
Surface-wetting laxatives, for example arachis oil and docusate, let water get into poo to soften it and make it easier to pass.
Can people with irritable bowel syndrome take it?
It's not a good idea for people with irritable bowel syndrome (IBS) to take lactulose.
Lactulose increases gas and bloating in the stomach, which can make IBS worse. Other types of laxative may be more suitable if you have IBS.
Can people with diabetes take it?
Yes, usually they can. If you have diabetes, ask your doctor or pharmacist whether lactulose is suitable you.
If you have diabetes and are taking normal doses of lactulose for constipation, the medicine will have little, if any, effect on your blood sugar levels.
But if you have diabetes and need to take high doses of lactulose for many months, the medicine may affect your blood sugar levels. In this case, monitor your blood sugar levels carefully and share the results with your doctor. Your diabetes treatment or diet may need to be adjusted.
Some people think that lactulose is the same as lactose, a sugar that can dangerously raise blood sugar levels. But lactulose is very different. It's a synthetic sugar that is broken down in the bowel so very little gets into your bloodstream.
Can I use lactulose after surgery?
It's quite common to have constipation after surgery. Using a laxative may help relieve the discomfort.
If you have constipation after an operation, it's fine to use lactulose syrup. It's gentler on the stomach muscles than some other types of laxative, like senna.
Will it affect my contraception?
Lactulose does not affect any type of contraception, including the combined pill or emergency contraception.
But if lactulose makes you sick (vomit) or have severe diarrhoea for more than 24 hours, your contraceptive pills may not protect you from pregnancy. Look on the pill packet to find out what to do.
Read more about what to do if you're on the pill and you're being sick or have diarrhoea.
Can I drive or ride a bike?
Taking lactulose should not affect your ability to drive or ride a bike.
Can I drink alcohol while taking lactulose?
Yes, you can drink alcohol with lactulose.
But try not to drink too much, as it could make you more likely to get diarrhoea.
Is there any food and drink I need to avoid?
You can eat and drink normally while taking lactulose.
It might help to cut down on foods such as pastries, puddings, sweets, cheese and cake for a while, as these foods can make constipation worse.
To help with constipation, eat more fibre, such as fresh fruit, vegetables and cereals, and drink plenty of water.
Can lifestyle changes help constipation?
It's often possible to improve constipation without having to use laxatives.
Before trying lactulose, or to stop constipation coming back, it may help to:
- get more fibre into your diet – aim for about 30g of fibre a day. High-fibre foods include fruit, vegetables and cereals. If you're not used to a high-fibre diet, increase the amount of fibre you eat gradually
- add bulking agents, such as wheat bran, oats or linseed, to your diet. These will help make your poo softer and easier to pass (although bran and fibre can sometimes make bloating worse)
- drink plenty of water – to keep poo soft
- exercise regularly – keeping your body active will help to keep your gut moving