Key takeaways:
Irritable bowel syndrome (IBS) is a common condition that affects the gut. It can cause constipation and diarrhea.
Polyethylene glycol (Miralax) may help ease some IBS symptoms, like infrequent or hard stools. It takes between 2 and 4 days to see changes in your stool from Miralax.
Miralax is safe for most people. But it’s not meant to be used alone as a long-term solution. Work with your healthcare team to develop a long-term IBS plan to manage your constipation.
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Irritable bowel syndrome (IBS) is a common condition that affects the gut. IBS symptoms vary from person to person, depending on what sub-type of IBS they have. IBS subtypes include IBS-C (constipation), IBS-D (diarrhea), IBS-M (mixed), and IBS-U (unclassified).
IBS-C is the most common sub-type. Many people with IBS-C struggle to find a treatment plan that can ease their hard or infrequent stools. Many people turn to over-the-counter (OTC) medications and other products for help.
If you’ve been thinking about trying polyethylene glycol (Miralax) for IBS, here’s what to know before you try it.
Does Miralax work for IBS?
Yes, Miralax does work for IBS-C. Miralax draws water from the colon into the bowel, making stool softer and easier to pass.
Miralax can help with IBS-C symptoms like:
Infrequent stools
Hard stools
Difficult-to-pass stools
Straining
In studies, people with IBS-C who took Miralax experienced more regular stooling patterns and had softer, easier-to-pass stools. But those same studies showed that Miralax didn’t help with other IBS symptoms, like bloating, abdominal pain, or gas.
Miralax is available at retail pharmacies and grocery stores. It’s also less expensive than some other medications used to treat constipation. This makes it a good choice as a first-line treatment because most people can access and afford it.
Though it’s often a first-used medication, experts point out a couple of unknowns, too, due to gaps in research:
Miralax and IBS-C: There haven’t been a lot of studies on how well Miralax works to treat IBS-C. So, it’s hard to know how well Miralax will work for most people.
Miralax vs. other laxatives: There haven’t been studies comparing Miralax to other laxatives for treating IBS-C. So, it’s also unclear if Miralax is always the best option.
Safety of long-term use: Miralax is FDA-approved for short-term use. There have been some studies looking at whether Miralax was safe to use every day. But these studies only looked at safety for up to a year. It’s not clear whether taking Miralax every day for longer periods of time is safe for everyone.
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How long does it take for Miralax to help with IBS?
It takes 2 to 4 days for Miralax to start working.
Miralax is an osmotic laxative. It draws water into the gut so that stool is softer and easier to pass. This effect also stimulates the gut a little bit, but not enough to produce a quick bowel movement. These effects take a few days to kick in. People start noticing changes in their bowel movements within 2 to 4 days of starting Miralax. You’ll see ongoing results, if you keep taking Miralax daily.
Miralax isn’t a stimulant laxative. Stimulant laxatives work by encouraging the gut to move, which produces a bowel movement. Stimulant laxatives produce a bowel movement within a few hours.
- Polyethylene Glycol 3350
- BentylDicyclomine
- HyosyneHyoscyamine
Miralax’s more gentle effect on the gut also means you’re less likely to experience side effects, like cramping, that are more common with stimulant laxatives.
Most people take 17 g of Miralax powder dissolved in 8 oz of liquid each day. But you can adjust the amount based on how well you respond to the medication. Some people may need to take less, and others may need to take more. It’s important to work with your healthcare team to find the right dose for you.
Who can take Miralax for IBS?
Miralax is safe for most people with IBS-C. But keep in mind that it won’t help with bloating or pain. In some cases, it might make these symptoms worse. So, talk with your healthcare team if you notice worsening symptoms while taking Miralax. They may recommend a different laxative to help with constipation symptoms.
Miralax isn’t a good option for people with IBS-D because Miralax can make diarrhea worse. It may be a good option for people with IBS-M or IBS-U, depending on their symptoms.
Talk with your healthcare team if you’re pregnant or nursing. Miralax is a category C medication. It may be safe, but there’s limited information on how it impacts human fetuses. Your healthcare team can review the risks and benefits of Miralax and help you decide if it’s the best choice for you.
What are the risks of using Miralax for IBS?
The most common side effects of Miralax include:
Nausea
Bloating
Cramping
Gas
If you already have these IBS symptoms, taking Miralax may make them worse.
There’s not a lot of information on how daily Miralax use over the long-term may impact health. A recent study showed that people who took OTC laxatives, including Miralax, were more likely to be diagnosed with dementia. Of course, this doesn’t mean that laxatives cause dementia. But it did raise the point that long-term safety studies are lacking. Your healthcare team can help you decide how to wisely use Miralax and other laxatives over the long term.
What is the best laxative for constipation from IBS?
Experts recommend osmotic laxatives, like Miralax, for IBS-C. But it’s important to know that laxatives are only one part of an IBS treatment plan.
You shouldn’t rely on laxatives by themselves for IBS treatment. Laxatives work best when used with other IBS treatments like:
Getting enough fiber
Medications to treat other IBS symptoms
Work with your healthcare team to create an IBS plan that addresses all of your symptoms.
Frequently asked questions
Miralax is FDA-approved to treat short-term constipation. There are some studies showing that it’s safe to take Miralax regularly for up to a year. But there’s not a lot of evidence showing Miralax is safe to take every day long term.
Yes, some laxatives can make IBS worse. Laxatives can worsen diarrhea if you have IBS-D. You also want to be careful using laxatives if you have IBS-M or IBS-U, since laxatives may cause loose stools. Laxatives may also worsen IBS symptoms, like bloating, cramping, and pain.
Miralax is a category C medication. The body doesn’t absorb a lot of Miralax, so experts don’t think it'll harm a developing fetus. But there’s no evidence showing this for sure. If you're pregnant or nursing, it’s best to discuss Miralax with your healthcare team before trying it.
Miralax is FDA-approved to treat short-term constipation. There are some studies showing that it’s safe to take Miralax regularly for up to a year. But there’s not a lot of evidence showing Miralax is safe to take every day long term.
Yes, some laxatives can make IBS worse. Laxatives can worsen diarrhea if you have IBS-D. You also want to be careful using laxatives if you have IBS-M or IBS-U, since laxatives may cause loose stools. Laxatives may also worsen IBS symptoms, like bloating, cramping, and pain.
Miralax is a category C medication. The body doesn’t absorb a lot of Miralax, so experts don’t think it'll harm a developing fetus. But there’s no evidence showing this for sure. If you're pregnant or nursing, it’s best to discuss Miralax with your healthcare team before trying it.
The bottom line
Polyethylene glycol (Miralax) is an over-the-counter laxative that’s FDA-approved to treat occasional constipation. Miralax may help ease hard or infrequent stools in people with irritable bowel syndrome with constipation (IBS-C). But it won’t help with IBS symptoms like cramping or bloating. Miralax can worsen diarrhea in people with IBS with diarrhea (IBS-D).
Why trust our experts?
References
American Gastroenterological Association. (2022). New AGA guidelines: A targeted approach to IBS-C and IBS-D treatment.
Buck, K. K., et al. (2005). Draft clinical review: Polyethylene glycol 3350 powder laxative. U.S. Food and Drug Administration.
Chang, L., et al. (2022). AGA clinical practice guideline on the pharmacological management of irritable bowel syndrome with constipation. Gastroenterology.
Chapman, R. W., et al. (2013). Randomized clinical trial: Macrogol/PEG 3350 plus electrolytes for treatment of patients with constipation associated with irritable bowel syndrome. The American Journal of Gastroenterology.
Dabaja, A., et al. (2023). Polyethylene Glycol. StatPearls.
Di Palma, J. A., et al. (2007). An open-label study of chronic polyethylene glycol laxative use in chronic constipation. Alimentary Pharmacology & Therapeutics.
Khoshoo, V., et al. (2006). Effect of a laxative with and without tegaserod in adolescents with constipation predominant irritable bowel syndrome. Alimentary Pharmacology & Therapeutics.
Lacy, B. E., et al. (2021). ACG clinical guideline: Management of irritable bowel syndrome. The American Journal of Gastroenterology.
Reuters. (2007). Miralax safe for chronic constipation.
Self, M. M., et al. (2014). Subtypes of irritable bowel syndrome in children and adolescents. Clinical Gastroenterology and Hepatology.
Yang, Z., et al. (2023). Association between regular laxative use and incident dementia in UK Biobank participants. Neurology.
