Key takeaways

  • MiraLAX is an over-the-counter laxative that works by pulling water into your colon to relieve constipation. Common mild side effects include bloating, gas, nausea, stomach cramping, and diarrhea or loose stools.
  • Serious side effects can include dehydration and electrolyte imbalance (especially in older adults or young children), rectal bleeding, severe abdominal pain that may signal a bowel blockage, or rare allergic reaction.
  • MiraLAX is intended for short-term use (up to 7 days over the counter). Stop taking it and talk with a healthcare professional if your constipation lasts more than 7 days or if you experience worsening symptoms.

MiraLAX (polyethylene glycol 3350) is a brand-name powder that’s mixed into a beverage and taken by mouth. It’s available over the counter and can be used for constipation or before a colonoscopy as a bowel preparation.

MiraLAX can cause certain side effects, though they are typically mild and temporary. These effects often last for a few days or weeks as your body adjusts to the medication. However, if they persist, become severe, or cause you concern, talk with your doctor or pharmacist.

The most common mild side effects reported by people taking MiraLAX include:

  • bloating
  • gas
  • nausea
  • stomach cramping
  • diarrhea or loose stools

What to do

Mild side effects typically go away once your body adjusts to MiraLAX. In the meantime, you can try the following:

  • If you have diarrhea or loose stools, you may be taking too much. Talk with your doctor or pharmacist about lowering your dose until your bowel movements are more solid.
  • MiraLAX works by pulling water into your colon. To help the process and prevent cramping, be sure to drink plenty of water throughout the day.
  • If MiraLAX makes you nauseous, try taking it with a small snack or meal to see if that settles your stomach.
  • For gas and bloating, light activity such as a brief walk can help move things through your digestive system more quickly.

If these side effects don’t go away after a few days or if they start to interfere with your daily life, contact your healthcare professional. They may recommend a different kind of laxative or alter your MiraLAX dosage or dosing schedule.

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Serious side effects from MiraLAX aren’t common, but they can occur. According to the drug’s prescribing information, you should be aware of the following side effects and symptoms:

Note: Stop MiraLAX use and see a doctor if your symptoms get worse or if your constipation lasts more than 7 days.

What to do

If you experience rectal bleeding, signs of an allergic reaction, or severe abdominal pain, stop taking MiraLAX and contact your doctor right away. They can help determine if the symptoms are related to the medication or a different condition and may recommend an alternative treatment.

Experiencing side effects? After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews its side effects. If you develop a side effect while taking this medication and want to report it to the FDA, you can visit MedWatch or call 800-FDA-1088.

MiraLAX is intended for short-term use. Talk with your doctor if you find you need to take it every day in order to maintain regular bowel movements.

For most people, side effects such as bloating and gas decrease over time as their body adjusts to MiraLAX. If you use this medication long-term under a doctor’s supervision, you likely won’t experience new symptoms, but the existing mild ones should resolve once you stop treatment.

Children usually experience the same side effects as adults, including bloating, gas, and stomach cramps. However, children are at a higher risk of dehydration if MiraLAX causes diarrhea.

It’s important to note that MiraLAX is only Food and Drug Administration (FDA)-approved for adults (ages 17 years and older). Use in younger children is considered “off-label,” so always consult their pediatrician regarding the proper dosage for your child.

MiraLAX is only recommended for over-the-counter (OTC) use for up to 7 days. Using it longer than a week without medical supervision or taking more than the recommended dose can lead to overuse side effects.

The primary risk is severe diarrhea, which can cause dehydration and dangerous electrolyte imbalances. If you think you’ve taken too much or are experiencing extreme dizziness or confusion, contact America’s Poison Centers or get medical help immediately.

Before taking MiraLAX, discuss your health history with your doctor. MiraLAX may not be right for you if you have certain medical conditions or other factors affecting your health.

Be sure to tell your doctor if any of the following apply to you:

Note: Ask a doctor before using MiraLAX if you have a sudden change in bowel habits that lasts over 2 weeks.

Disclaimer: While Medical News Today strives for factual, comprehensive, and current drug information, this article is not a substitute for a licensed healthcare professional’s expertise. Always consult a doctor before taking or discontinuing any medication. Drug information is subject to change and may not cover all uses, directions, precautions, warnings, interactions, reactions, or adverse effects. The lack of a warning does not guarantee a drug’s safety, effectiveness, or appropriateness for all patients or specific uses. Learn more about our approach to content integrity.