Miralax Safety and Side Effects

If you have consulted with your healthcare provider about your experience of constipation, it is very likely that you walked away with the recommendation to try Miralax. In this overview, you will get some basic information about this over-the-counter treatment so you will have a good sense of its safety, side effects, and effectiveness for treating constipation.

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What Is Miralax?

Miralax (polyethylene glycol 3350) is a medication that was designed to treat occasional episodes of constipation. Miralax is classified as an osmotic laxative because it draws fluid into your bowels. This action results in softer, easier-to-pass stools, and increases the frequency of bowel movements.

Interestingly, the formulation of Miralax, when combined with electrolytes, is often used to prep the bowels prior to a colonoscopy or intestinal surgery.


  • For short-term use: Miralax has been demonstrated to be effective in relieving the symptoms of occasional bouts of constipation. However, keep in mind that it may take one to three days for the medication to result in a bowel movement.
  • For chronic idiopathic constipation (CIC): An institution no less impressive than the American College of Gastroenterology (ACG), in its latest review, has concluded that Miralax is an effective treatment for improving the symptoms of CIC. In contrast to other laxative options, typically the dosage of Miralax does not have to be raised over time to continue to be effective. In some cases, the dosage may even be lowered and still be of help. For CIC, research has indicated that Miralax is more effective than placebo in easing the symptoms of constipation—this includes prompting regular bowel movements, normalizing stool consistency, and reducing straining during bowel movements. It also appears that when Miralax is taken on a regular basis that it also might reduce bloating, abdominal pain, flatulence, and burping.
  • For irritable bowel syndrome (IBS): In several studies on the subject, results indicate that Miralax is good at doing what it is designed for—easing symptoms of constipation. But, the medication does not appear to be effective in easing abdominal pain or the other overall symptoms of IBS.

How to Take Miralax

Miralax is a powder that you mix with a liquid. You can choose your preferred liquid—water, coffee, tea, juice, or soda—and measure out an 8-ounce glass. Stir the Miralax powder in and thoroughly mix it until it dissolves and then drink it down right away. Be sure to follow the package directions exactly. For short-term use, you would typically take Miralax once a day for a period of one week. Be sure to follow the package directions exactly.

If you have been diagnosed with CIC or constipation-predominant IBS (IBS-C) and thus deal with constipation on a chronic basis, you should speak with your healthcare provider as to whether or not to use Miralax for longer than the recommended one-week period.

Side Effects

Miralax is generally considered to be a safe, well-tolerated medication. Research studies have not indicated any significant negative side effects. A very small percentage of people who participated in research studies on the medication reported symptoms such as abdominal pain, bloating, and vomiting - all of which disappeared as soon as they stopped taking Miralax. Some studies have indicated that Miralax is less likely to cause bloating or flatulence than other osmotic laxatives.

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