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MiraLAX Review: Safety, Effectiveness, Pros and Cons

Written by Markita Lewis, MS, RD

Published on September 28, 2021

Our Expert Rating:

4.0

About This Rating
The average rating of this product is calculated based on the evaluation of the following factors:
  • Support for Claims:4.0
  • Ingredient Safety:3.0
  • Value for the Price:5.0
  • Brand Transparency:4.0

MiraLAX is an FDA-approved osmotic laxative to help individuals seek relief from constipation. While it may take a little longer to work when compared to some laxatives, it is effective, well-tolerated, and worth trying when you’re dealing with constipation.

MiraLAX Review: Safety, Effectiveness, Pros and Cons
Photo credit: iStock.com/mapichai

Pros

  • Can be mixed into any beverage
  • Effectiveness of product is well-researched
  • Fewer side effects compared to some other types of laxatives

Cons

  • Potentially long time to work (within 1–3 days after use)
  • Inconsistency of pricing across retailers
  • No FDA approval for children

What Is MiraLAX?

MiraLAX, also known as polyethylene glycol 3350, is an FDA-approved osmotic laxative manufactured by the pharmaceutical company Bayer.

This over-the-counter medication is meant for helping people achieve effective yet gentle relief from occasional constipation.

Constipation is defined as having fewer than three bowel movements per week or having fewer bowel movements than usual, excessive straining when going, difficult and painful bowel movements, having hard, dry, or lumpy stool, or the feeling of an incomplete bowel movement.

Constipation can be tied to several factors, including a lack of fiber, taking certain medications, not listening to your body’s signals to go to the bathroom, and dehydration.

The colon naturally tries to be as efficient as possible in reabsorbing any excess water from your bowels to be used in the body, and this is especially so when you’re dehydrated.

This absorption of water can result in you having dry stools that can’t move well through the colon and potential constipation.

Osmotic laxatives such as polyethylene glycol help you poop by drawing more water into your stools. When there is more moisture in your stools, they become softer and easier to pass.

MiraLAX is FDA-approved for use only in individuals ages 17 years and older.

There isn’t FDA approval for children due to a lack of clinical studies, but children may receive MiraLAX if under the supervision of their pediatrician or gastroenterologist.

Typical use of MiraLAX is once daily for no more than seven days.

When taking MiraLAX from the bottle, measure 17 grams of powder into the bottle’s cap (the white section in cap) and dissolve into 4–8 oz of any beverage to drink.

If using the MiraLAX Mix-In Pax single-dose packets, mix a single packet with 4–8 oz of a beverage and enjoy.

MiraLAX is made by the German pharmaceutical and life sciences company Bayer, which develops products for consumer health, pharmaceuticals, and crop science.

Is MiraLAX Effective?

The active ingredient in MiraLAX is polyethylene glycol 3350 (also abbreviated as PEG 3350).

MiraLAX does not contain any additional electrolytes compared to other formulations of PEG-3350, like GoLytely.

MiraLAX has been studied for the last 20 years in adults and children.

One of the first studies on MiraLAX’s effectiveness was published in 2000, where 151 constipated adults (mostly female) were assigned 17 g of PEG-3350 or a placebo for two weeks.

By the end of the study, bowel movement frequency and stool consistency, and ease of passage had significantly improved in the PEG-3350 group compared to a placebo.

In 2011, a published review on polyethylene glycol-3350’s efficacy consistently found that PEG-3350 was significantly better at relieving constipation when compared to a placebo or alternative medication.

Participants in these studies experienced increased bowel movements, improved stool consistency, less straining, and more satisfaction in the quality of their bowel movements.

One of these studies was a multicenter, 12-month open-label study that found that most chronic constipation patients who used PEG-3350 had improvement in their constipation.

Approximately 80–88% of patients reported complete or considerable relief from constipation at each quarterly check-in, and 85–92% no longer met the Rome criteria for constipation at their visit.

Some of the studies on MiraLAX show that this medication has its best efficacy on the second week of use, despite the over-the-counter recommendations that it should only be used up to seven days in a row.

One 2002 study did find that a single 68 g dose of MiraLAX (4 times the recommended dose) was able to increase the likelihood of a bowel movement within the first 24 hours of use.

Other studies only reported bowel movement frequency per week, so it is hard to determine precisely when participants had their first bowel movement and if it was within 1–3 days.

While MiraLAX has not been FDA approved for children, there are several studies on MiraLAX as a treatment for functional constipation and fecal impaction in children.

A 2014 meta-analysis was published concerning the effectiveness and safety of polyethylene glycol-based laxatives for the treatment of constipation in children.

Children who received the polyethylene glycol-based laxatives had more successful bowel movements when compared to those taking other laxatives.

The polyethylene glycol-based laxatives were also tolerated better by children.

Summary 

Research shows that MiraLAX can improve symptoms of constipation and improve bowel movement frequency in adults and children.

While there is limited research on MiraLAX working within the first 1–3 days of use, people experience significant improvement in bowel movements within a week.

Verdict on Claimed Benefits

Below is our summary of the available evidence for the claimed benefits of MiraLAX based on the available research:

  • Relieves occasional constipationGold Star Evidence
  • Generally produces a bowel movement in 1 to 3 daysModerate Evidence

Studies consistently show that MiraLAX helps improve symptoms of constipation in adults and children.

The data on whether the recommended dose of 17 g per day can cause a bowel movement within 1–3 days is lacking, but there is solid evidence that there is improvement in bowel movements within the first week of use.

Side Effects, Dosage, and Safety

MiraLAX should be used once a day for no more than seven days. Your doctor may recommend alternate dosing depending on your individual needs.

Do not take more than the recommended dose on your own.

To take a standard serving of MiraLAX from the bottle, measure 17 grams of powder into the bottle’s cap (the white section in cap) and dissolve into 4–8 oz of any beverage to drink (MiraLAX is not affected by the beverage’s temperature).

If using the MiraLAX Mix-In Pax single-dose packets, mix a single packet with 4–8 oz of a beverage and enjoy.

While MiraLAX is not FDA-approved for children, some pediatricians and pediatric gastroenterologists may recommend the use of MiraLAX.

I recommend only using MiraLAX under the direct supervision of medical professionals because the dosing and frequency of use may differ depending on your child’s size, age, and condition.

MiraLAX promotes itself as not having any significant side effects like gas, bloating, cramping, or urgency for bowel movements.

However, long-term use of MiraLAX may result in mild symptoms including diarrhea, gas, loose stools, nausea, and abdominal pain.

Children taking polyethylene glycol medications may experience diarrhea, abdominal pain, nausea or vomiting, bloating, gas, pain or straining with bowel movements, hard stools, and rectal bleeding.

There is no definitive research that confirms a relationship between MiraLAX or other polyethylene glycol medications and neurological or neuropsychiatric side effects.

MiraLAX is gluten-free, sugar-free, and free of preservatives. Avoid using MiraLAX if you have an allergy to polyethylene glycol.

MiraLAX is contraindicated for use if you have a history of kidney disease, except for under a doctor’s supervision.

Remember to speak with your doctor first before taking MiraLAX to see if it is safe for you.

Cost and Where to Buy

MiraLAX is available to purchase as a bottle or as single-dose packets for your convenience. Both come in different sizes, so you can buy the amount that works best for you.

MiraLAX Bottle Sizes:

  • 4.09 oz bottle (7 doses)
  • 8.3 oz bottle (14 doses)
  • 17.9 oz bottle (30 doses)
  • 26.9 oz bottle (45 doses)

MiraLAX Mix-In Pax:

  • 10-Dose single serve sachets
  • 20-Dose single serve sachets

MiraLAX can be purchased from several major retailers in-person and online, including CVS, Rite Aid, Walmart, Target, and Amazon.

The MiraLAX website has a search feature so that you can find the closest retailer that sells their product.

However, there is a difference in price depending on where you purchase MiraLAX.

When I compared the costs between different online retailers, I found that purchasing through Walmart or Target online was the cheapest option, while Amazon had the highest prices.

For example, a 7-dose bottle purchased from Target costs only $6.89, while it costs $10.88 to $14.91 on Amazon, depending on the storefront.

You can save $1 on your purchase by downloading a coupon from the official MiraLAX website. Return policies are dependent on individual retailers.

Before you purchase MiraLAX, you can also speak with your doctor to see if you can get a free sample of this product.

MiraLAX is also FSA/HAS eligible for reimbursement with a prescription from your doctor.

Summary

MiraLAX, when purchased from the correct retailer, is a reasonably priced osmotic laxative powder compared to other generic laxative powders. MiraLAX is worth its cost because it is both effective and accessible in price.

How MiraLAX Compares to Alternatives

MiraLAX is an affordably priced and effective polyethylene glycol osmotic laxative available both over-the-counter and as a prescription.

Compared to other osmotic laxatives, MiraLAX appears to be more effective and better tolerated.

A 2010 review and meta-analysis concerning the use of lactulose versus polyethylene glycol for chronic constipation found that bowel movement outcomes were better in children and adults who took polyethylene glycol instead of lactulose.

MiraLAX does have a slower action time, which could be a problem for people experiencing considerable distress from their constipation.

Stimulant laxatives, like Dulcolax or Ex-Lax, or stool softeners may be better suited to meet the needs of those individuals.

Bulk-forming laxatives, like Metamucil, do hold some advantage over MiraLAX in that they are safe for long-term use.

MiraLAX, on the other hand, should only be taken up to 7 days consecutively unless instructed by a physician.

Because the effects of MiraLAX diminish after discontinuation, bulk-forming laxatives can be a way to help people consistently have relief from constipation.

Summary

MiraLAX may help consumers achieve superior results in constipation relief when compared to other osmotic laxatives.

Alternative laxative types have an advantage through a faster time to action, and bulk-forming laxatives are better for long-term use.

Despite this, MiraLAX is still an optimal choice for an osmotic laxative.

Frequently Asked Questions About MiraLAX

  • How does MiraLAX work?

    MiraLAX works by increasing the amount of water into your stools, making it easier for your poop to move through the colon.

  • How long does it take for MiraLAX to start working?

    MiraLAX usually helps you have a bowel movement within 1–3 days after use.

  • How do you take MiraLAX?

    If using MiraLAX from the bottle, measure 17 grams of powder into the bottle’s cap and dissolve into 4-8 oz of any beverage to drink (MiraLAX is not affected by the beverage’s temperature).

    When using the MiraLAX Mix-In Pax single-dose packets, mix a single packet with 4-8 oz of a beverage and enjoy.

  • When is the best time to take MiraLAX?

    Because MiraLAX does not start working instantaneously, there is no recommended time of day to take this product. The best time to take MiraLAX is when you are feeling signs of constipation.

  • What are the side effects of taking MiraLAX?

    Long-term use of MiraLAX may result in mild symptoms including diarrhea, gas, loose stools, nausea, and abdominal pain.

    Children taking polyethylene glycol medications may experience diarrhea, abdominal pain, nausea or vomiting, bloating, gas, pain and straining with bowel movements, hard stools, and rectal bleeding.

  • Is MiraLAX safe for kids?

    MiraLAX is currently approved by the FDA for adults only, due to the lack of clinical trials in children.

    You should speak with your child’s pediatrician or pediatric gastroenterologist first to see if MiraLAX is right for your child, and for appropriate dosing.

  • Is MiraLAX safe during pregnancy?

    Before starting use, it is recommended to speak with your doctor if you can take MiraLAX while pregnant or breastfeeding.

    Research suggests that osmotic laxatives (like MiraLAX) should only have short-term or occasional use to avoid electrolyte imbalances or dehydration.

  • Can I take MiraLAX daily?

    MiraLAX should only be used for up to seven consecutive days. If you are still experiencing constipation after one week, please stop using MiraLAX and consult your doctor.

The Bottom Line

MiraLAX is an effective and well-tolerated osmotic laxative to fight constipation.

This over-the-counter product is primarily for adults who experience constipation and need help in achieving a bowel movement.

MiraLAX may be a good alternative for individuals who want to avoid the side effects of stimulant laxatives and are okay with a slightly longer wait time for relief.

While working in a clinical inpatient setting, I have regularly recommended to doctors that my patients receive MiraLAX to help with constipation.

I’ve witnessed first-hand how MiraLAX can help with some of the discomforts of constipation and get people back to regular bowel movements.

Before starting MiraLAX, be sure to speak with your doctor first to see if it is appropriate for you.

This holds especially true if giving MiraLAX to a child under the age of 17 or someone who has a history of kidney disease or existing gastrointestinal issues.

A Word from Our RD

Constipation is natural and happens to all of us at some time. Taking a laxative can be helpful when we’re feeling discomfort and need a little help in the bathroom.

To reduce the frequency of constipation, there are small actions that you can take.

The first action is to add fiber into the diet, both soluble and insoluble fiber.

You can get more fiber in your diet by gradually increasing the number of fruits, vegetables, beans, peas, lentils, nuts, seeds, and whole grains in your diet.

Increasing your fiber intake slowly can help reduce any discomfort you may feel as your body and gut bacteria adjust.

Eventually, you want to aim for at least 21–38 g of fiber daily.

Drinking more water and getting fluid in your diet is another helpful step in reducing constipation.

The likelihood of constipation increases if you’re dehydrated, so making an effort to drink more water or having foods with high water content (think soups, fruits) can help.

When increasing your fiber intake, it’s vital to increase your water intake to prevent your poops from getting too bulky.

When you move your body, your poops start moving too. Research suggests that aerobic and cardio exercise can help relieve constipation.

If you notice that you’re constipated and under a lot of stress, your stress may be contributing to your constipation.

Stress-management techniques including deep breathing, getting enough rest, and other calming activities may help with constipation.

Last but not least, don’t hold it. Holding your poop may lead to impaction of bowel movements, distended bowels, and decreased sensation for noticing when to go.

When you feel the urge, try to go to the bathroom as soon as possible.

If you experience chronic constipation or have no relief after implementing some of these techniques, speak with your doctor.

Chronic constipation may be indicative of certain gastrointestinal conditions that may require further assessment and other treatment methods.

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