Managing Side Effects of laxatives: What to Expect and What to Do
If you have experienced bloating, gas, or mild cramps since starting laxative treatment, you are not doing anything wrong. These are common and well-understood side effects, and they usually improve on their own within a few days. This article explains why they happen, what helps, and when to seek advice.
What Should I Do If Lactulose Causes Diarrhoea?
Diarrhoea is a very common side effect of lactulose, occurring in more than one in ten people 1. Lactulose works by drawing water into the colon to soften stool — if it draws in more water than necessary, the result is loose or watery stools 1. This may need to be addressed because persistent diarrhoea can lead to fluid loss, and in some people, can affect the body’s mineral balance 1.
When taken as per recommended dosage, you should get a gentle, comfortable effect without loose stools. If diarrhoea occurs, reducing your dose is the key step 1, 2.
While your stool consistency settles, make sure you drink plenty of fluids — water or diluted squash are ideal — to replace what you are losing 3. If reducing the dose does not resolve the diarrhoea within a couple of days, consider reducing further, stopping treatment or consult a healthcare professional for advice 1.
How Can I Reduce Bloating and Flatulence When Taking Lactulose?
Bloating and gas are common side effects of lactulose, caused by the way the medicine works in the gut 1, 4. When lactulose reaches the colon, gut bacteria break it down and produce hydrogen and methane — which is what causes these symptoms 4.
These effects are often temporary and tend to improve as your body adjusts 1, 4. A few simple adjustments can help in the meantime:
- Adjust when you take it. Taking lactulose between meals, rather than immediately before or after eating, may reduce the sensation of bloating 3. If you take a single daily dose, you should only take it at the same time each day 1.
- Reduce gas-forming foods temporarily. Foods such as lentils, peas, beans, and onions can contribute to gas and bloating. Avoiding these while you adjust to lactulose may help reduce symptoms 3.
- Consider your meal pattern. Eating smaller, more frequent meals and taking your time eating and drinking may also help reduce gas and bloating 3.
- Stay hydrated. Drinking around 1.5 to 2 litres of fluid per day is recommended throughout treatment 1.
If bloating is bothersome and does not improve, a modest dose reduction is worth trying 1, 4. If it persists despite these adjustments, speak with your pharmacist or healthcare provider, who can advise whether a different approach might suit you better.
What Should I Do If Lactulose Is Causing Nausea or Vomiting?
Feeling of vomiting (nausea) or actual vomiting, are recognised side effects of lactulose, occurring in more than one in a hundred people 1, 3.
If you are vomiting, drink plenty of fluids in small, frequent sips — water or diluted squash — to avoid dehydration 3. Do not take other medicines to treat vomiting without first speaking to a pharmacist or doctor 3. If vomiting does not improve after a couple of days, or if it occurs alongside diarrhoea, contact your doctor 1, 3.
What Should I Do If Lactulose Is Causing Abdominal Cramps or Discomfort?
Abdominal cramps are a recognised side effect of lactulose 1. When they do occur, they are usually mild and tend to settle with time 4. Some people may notice a general sense of activity in the gut — this is simply the bowel responding to treatment and is nothing to be alarmed about.
For many people, cramping is temporary and tends to ease as the gut adjusts 4. Applying a heat pad or a warm water bottle (covered, to protect the skin) to your abdomen can provide gentle relief while things settle 3. If it remains bothersome, reducing the dose slightly — in the same way as for diarrhoea — is a practical first step 1, 4.
Severe or persistent abdominal pain is not an expected side effect at recommended constipation doses and is worth discussing with a healthcare professional 1. If cramps are more than mild, stop taking lactulose and contact a healthcare professional 1.
Does Reducing the Dose of Lactulose Help Reduce Side Effects?
Reducing your dose is a recommended approach for managing the gastrointestinal side effects 1, 2. These side effects tend to be dose-dependent — meaning they are more likely at higher doses — so taking a smaller amount can help reduce them 1, 4.
This is not a compromise or a sign that (lactulose) is failing. If the starting dose causes side effects, it can be reduced gradually until you find an amount that produces comfortable, regular soft stools without causing diarrhoea or discomfort 1, 2. Some people need only a small daily dose, while others may need more.
If you experience diarrhoea, it could be a signal that the dose is too high and should be reduced 1. If bloating or cramping is bothersome, a smaller dose may help 1, 4. Gastrointestinal side effects of lactulose are often temporary and tend to improve when the dose is adjusted to suit you 1, 4.
If reducing the dose means constipation returns, you may wish to speak with your pharmacist — they can help you find the right balance between effectiveness and comfort.
When Should Side Effects from Lactulose Prompt Me to Speak to a Doctor?
Most side effects from lactulose at recommended constipation doses are mild and temporary. However, some symptoms do need medical attention — this section explains what to look out for.
Severe or prolonged diarrhoea. Diarrhoea that continues for more than a couple of days despite reducing the dose, or that is severe and watery, is worth seeking medical advice about 1, 3. Persistent diarrhoea can cause fluid loss and affect the body’s mineral balance — most notably levels of potassium, magnesium, and sodium — which can cause muscle cramps, weakness, or an irregular heartbeat 1, 3, 4. Older people and those who are debilitated may need closer monitoring of fluid and mineral levels if diarrhoea occurs 1, 4.
Signs of dehydration. These include passing less urine than usual or having dark, strong-smelling urine 3. If you notice these signs, make sure you are drinking plenty of fluids — water or diluted squash are ideal 3. If you are concerned or symptoms do not improve, contact a healthcare professional.
Signs of electrolyte disturbance. If you experience muscle cramps, weakness, or an irregular heartbeat alongside diarrhoea or vomiting, this could indicate an imbalance in your body’s mineral levels 3. Seek medical advice if this happens 3.
Severe abdominal pain. Severe abdominal pain is not an expected side effect at recommended constipation doses and is worth discussing with a healthcare professional 1. If you experience severe or worsening cramps, particularly alongside abdominal bloating, seek medical advice — a doctor can assess whether anything else might be causing your symptoms 1.
Prolonged use without improvement. If constipation has not improved after several days (2-3 days) of treatment, 1 or if you find yourself relying on lactulose continuously over a long period without identifying and addressing the underlying cause, it may be worth seeking advice from a healthcare professional. Those taking lactulose long-term should have their electrolyte levels monitored periodically, as advised by their doctor 1, 2, 4.
What You Can Do
- Reduce your dose if you experience diarrhoea, bloating, or cramping — a smaller amount may be all you need
- Drink plenty of fluids throughout treatment — water or diluted squash are ideal
- Take your dose between meals and at the same time each day
- If you experience nausea, try taking your dose with food or diluted in water
- Avoid gas-forming foods such as lentils, peas, beans, and onions while your body adjusts
Contact your pharmacist or doctor if side effects are severe, persistent, or accompanied by any of the symptoms described above.
Conclusion
Side effects from lactulose are common but are generally well tolerated and temporary 1, 4. The good news is that there is usually something you can do — whether that is adjusting your dose, changing when you take it, or making small changes to what you eat and drink. For many people, symptoms settle as the body adjusts and the right dose is found. If you have any concerns at any point, your pharmacist is a good first point of contact.
FAQ
Yes — gastrointestinal side effects such as flatulence, bloating, and mild abdominal cramps affect up to one in ten people taking lactulose 1. They occur because lactulose is broken down by bacteria in the colon, which produces hydrogen and methane 4. These effects are often temporary and tend to improve as your body adjusts 1, 4. Diarrhoea is more common, occurring in more than one in ten people, particularly at higher doses 1, 3.
When lactulose reaches the colon, it is broken down by bacteria in a fermentation process that produces gases, including hydrogen and methane. This gas production is what causes flatulence and bloating 4. The effect tends to be dose-dependent, so if flatulence is bothersome, reducing the dose slightly is worth trying 1, 4.
Bloating and flatulence are often temporary and tend to improve as your body adjusts 1, 4. Taking your dose between meals, avoiding gas-forming foods temporarily, and drinking enough fluids can all help in the meantime 1, 3.
Diarrhoea while taking lactulose could be a signal that the dose is too high and worth reducing 1. Make sure you are also drinking plenty of fluids — water or diluted squash are ideal 3. Do not take anti-diarrhoeal medicines without first speaking to a pharmacist or doctor 3. If diarrhoea persists after reducing the dose, consider reducing further or stopping treatment 1, 2. If you take the combined pill or progestogen-only pill and have severe diarrhoea for more than 24 hours, your contraception may not protect you from pregnancy — check the pill packet for advice 3.
Yes — the dose is designed to be adjusted to suit you, and reducing it if you experience side effects is recommended 1, 2. The aim is to find an amount that produces comfortable, regular soft stools without causing diarrhoea or discomfort 1, 2. If reducing the dose means constipation returns, consider speaking with your pharmacist to find the right balance.
Yes, for mild cramping. Applying a covered heat pad or warm water bottle to the abdomen, staying hydrated, and avoiding gas-producing foods temporarily can all help 3. These cramps often ease as the body adjusts to treatment 4. If cramps are severe or worsening, speak with a doctor 1.
You should not take other medicines to manage side effects from lactulose without first checking with a pharmacist or doctor 3. In particular, anti-diarrhoeal medicines should not be used without guidance 3. Some pharmacy remedies for gas and bloating, such as charcoal tablets or simeticone, may help — but check with a pharmacist first to make sure they are suitable for you 3.
Stop taking lactulose and seek medical advice if you experience severe abdominal pain, signs of dehydration (passing less urine than usual or dark, strong-smelling urine), signs of electrolyte disturbance (muscle cramps, weakness, or an irregular heartbeat), or any signs of a serious allergic reaction 1, 3. If milder side effects do not improve after reducing your dose, speak with your pharmacist 1, 2.
Yes — gastrointestinal side effects such as flatulence, bloating, and mild abdominal cramps affect up to one in ten people taking lactulose 1. They occur because lactulose is broken down by bacteria in the colon, which produces hydrogen and methane 4. These effects are often temporary and tend to improve as your body adjusts 1, 4. Diarrhoea is more common, occurring in more than one in ten people, particularly at higher doses 1, 3.
For many people, yes — side effects such as flatulence, bloating, and mild cramping are often temporary and tend to improve as your body adjusts 1, 4. Diarrhoea tends to resolve when the dose is reduced 1. Serious side effects are rare and are generally associated with doses that are too high 1, 4. Finding the right dose for you is the key to getting the most out of lactulose comfortably.
This article was written with the assistance of generative AI technology and reviewed for accuracy.
