Best time of day to give a laxative such as Miralax?


"What is the best time of day to give Miralax to my 3-year-old? Should we give it to him at the same time each day? Approximately how long does it take to produce stool? I don't want it to interfere with his nap at 2pm. He eats breakfast at 9am and lunch at 12:30pm. Also, we're concerned about the 2 days a week he goes to preschool. Do we wait to give him the Miralax until he gets home or will that throw off his schedule?"



Miralax is a water retention laxative which, at the correct dose, works continuously in the large intestine to keep stool soft and moist. Unlike with a stimulant laxative (e.g., Ex-Lax) there is no predictable time when Miralax produces a bowel movement. Typically, when a functionally constipated child is withholding stool especially a child your son’s age, we are more concerned about him just having a bowel movement every day than we are about the exact time of day it occurs. Scheduling comes later. I always recommend giving Miralax at approximately the same time every day either in the morning or in the afternoon/early evening.









When to Stop Laxatives

The mother of a 5 year old boy with all the symptoms of functional constipation was correctly told by her child's pediatrician to start him on Miralax but incorrectly told to stop the Miralax after only 2 weeks.  As expected, while taking the Miralax his stool softened and he started to have BMs more frequently, but he quickly regressed when the Miralax was stopped. 

Based on the pediatrician's initial recommendation, this mother understandably thought that the laxative should only be given for two weeks then stopped. Not surprisingly when she contacted me she was stuck in a unsuccessful "start-stop-start" Miralax routine.

In an earlier post I explained how stopping laxatives too soon is one of the two most common mistakes made by parents and pediatricians. And as I discuss in my book, laxatives must be continued long enough for a child to stop withholding and for the child's rectum to shrink back to its normal size. This can take anywhere from 6-12 months or longer in some children. The longer a child has had functional constipation, the longer it will take for the rectum to shrink back. 

I know this seems like a long time, but there is, unfortunately, no quick fix for functional constipation or encopresis.

Poop in Your Child's Underwear: Encopresis or Not Wiping?

The treatment of encopresis requires parents to keep track of poop accidents so that they can appropriately add or change the laxative or other treatment their child may be on (see the “Weekly Laxative and Stool Record” in my book, The Ins and Outs of Poop).

When I ask parents to describe the size and consistency of their child’s accidents, they will sometimes say, “I’m not sure if it’s an accident or if he/she just didn’t wipe, or wipe completely.” This is an important distinction because changes in laxatives or their doses is often based on the frequency, size and appearance of a child’s accidents.  If a parent doesn't know or is just guessing whether a child had an accident, the data they are using to make this decision is problematic.

Generally, poor or no wiping results in a brown stain or a thin smear. Anything more than a stain or thin smear is defined as an accident.

(One caution, however, about loose or liquid-like stools. These are sometimes mislabeled as accidents caused by constipation when they are not. As described in detail in my book, too much of a laxative (e.g. Miralax) can cause incontinence.)

Is it safe to give my child Miralax?

Parents frequently ask me if it is safe to give their child a PEG laxative such as Miralax. Some of these parents have read on the internet or have been told by a friend that these laxatives cause "problems" in children. My answer is the same as that given by most pediatricians or pediatric gastroenterologists. Based on experience, these laxatives are safe.

The vast majority of children taking PEG 3350 experience no behavioral or psychiatric problems. However, for years the FDA has received occasional reports of tremors, tics and obsessive-compulsive behaviors in children taking PEG laxatives but it is not known whether the laxatives are the cause.

As reported early this year in the New York Times, the FDA has asked a group of doctors at the Children’s Hospital of Philadelphia to study the absorption of PEG 3350 in children, especially the very young and chronically constipated. The study is intended to find out whether PEG 3350 is absorbed in the intestines by young children and whether the use of PEG laxatives is linked to the development of behavioral or psychiatric problems. (www.

If your child is chronically constipated and your child's healthcare provider has recommended a PEG laxative, you can be reassured that there is currently no scientifically validated evidence that PEG laxatives are unsafe for children.

Beware of Laxative Scare Mongers!

The mother of a child with chronic constipation recently wrote to me in a panic after reading an internet article (though as I note below, it is actually a well-disguised advertisement for the author's product) titled   “Is MiraLAX the Next Vioxx? No, It's Much Worse!” She said that, on Miralax, her daughter is “now pooping every day” and “has made major progress towards pooping on the toilet”. However, having read the article, she decided to stop giving her daughter Miralax. In its place, she said that she was going to try some “natural alternatives”.

In other words, the article scared this mother into not giving her child a laxative that is safe and effective and replacing it with natural remedies which are helpful for occasional constipation but which are largely ineffective for treating chronic constipation (encopresis).

The author of this article very cleverly uses half-truths to deceive readers into believing that Miralax causes a host of neurologic disorders such as autism, dementia, depression, schizophrenia, multiple sclerosis, Alzheimer’s disease and even encopresis!

The active ingredient in Miralax is polyethylene glycol 3350 (PEG 3350), NOT ethylene glycol. However, the author leads people to believe that PEG 3350 is exactly the same as ethylene glycol which, when used in products such as “automotive antifreeze and brake fluid“, can cause neurologic problems.  There is no scientific evidence that laxatives containing PEG 3350 cause neurologic or neuropsychiatric disorders.

When read carefully, this article is no more than a well-disguised advertisement for a scientifically untested and non-FDA approved combination of supplements and probiotics developed by the author for a veritable shopping list of conditions:  “chronic constipation, bloating, diarrhea, irritable bowel disease, diverticulosis, depressed immunity, chronic fatigue, anemia, infertility, amenorrhea, acne, hair loss, graying hair, premature aging, pre-diabetes, diabetes, respiratory and urogenital infections" and on and on.

And, as if this wasn’t enough to scare parents into discontinuing a safe and effective treatment for childhood constipation, the author recommends stopping giving your child FIBER because he says it makes stools so big that they hurt. As any medical professional will tell you, fiber, just like PEG laxatives, may make stools bigger but it also makes them softer so they do not hurt

Do not believe everything people tell you about laxatives, especially on the internet. My advice? When in doubt, ask your pediatric healthcare provider.

Enemas and Suppositories for Encopresis

Even though many of the parents I talk to have never had a rectal laxative themselves, they resist giving them to their children because they erroneously believe that they “hurt”. This is unfortunate because there are many children with encopresis who can and do benefit from them.

With PEG oral laxatives, such as Miralax, the time between administration and defecation is slow and unpredictable. Because there is no standard dose, the unpredictable response makes it difficult to determine the most efficacious dose whether it is for conducting a cleanout or for helping a child have a large, soft bowel movement every day without accidents. If we give too little laxative, the child’s stool remains dry and difficult to pass. If we give too much laxative, the child’s stool becomes almost liquid and may “leak” out.

However, the time between the administration of a rectal laxative and defecation is typically very brief, usually within 1-5 minutes, if not immediate. When given correctly (see Chapter 14 of my book), rectal laxatives will empty approximately ¼ of your child’s large intestine thereby reducing the likelihood of accidents.

Another benefit of an enema or suppository is an increase in the efficacy of rewards used to reinforce pooping on the toilet. In other words, the almost immediate bowel movement on the toilet following a rectal laxative allows for an equally immediate reinforcement for pooping on the toilet. As I explain in my book, the immediate and frequent reinforcement of a new behavior leads to faster learning of that behavior than when reinforcement is delayed or infrequent.

“He Won’t Drink All of His Poop Medicine!”

A problem I hear over and over from parents is that they are unable to get their child to finish all of their PEG laxative. Chapter 13 of my book contains a section titled, “How to get children to drink laxatives.” One suggestion is to mix the powder predissolved in a cold food such as ice cream, yogurt or a smoothie.

Recently, a mother told me about another cold food that works well for her child:

“I have found a way to be certain that my son gets all of his laxative. I have always had trouble making sure he drinks all of the juice I mixed it in. Recently, my mom bought us a Zoku popsicle maker. I make him a popsicle every night with his dose mixed in and he looks forward to it. He eats the entire popsicle, and, therefore, I know he has finished “drinking” all of his poop medicine.”

Popsicles! What a great idea, especially during these warm summer days.  Thanks to this mother for emailing!

Can laxatives cause poop accidents?

The mother of a child with encopresis recently told me that when she asked her pediatrician if Miralax might be the cause of her son’s frequent poop accidents, her pediatrician said, “Absolutely not!  In all my years of practice I have never seen Miralax cause accidents!” 

My first thought was that this doctor must not have treated many children with encopresis.

Any PEG or water retention laxative such as Miralax can cause stool to leak, sometimes uncontrollably, if given in unnecessarily high doses. This is, unfortunately, very common. In my experience, the main reason why children are unintentionally given more (or sometimes less) laxative than they need is because parents and even some healthcare professionals think that “one cap” of the PEG powder is the “standard dose” even for children, so that is how it is typically prescribed. But, often that is far more than the child needs.

The last thing a child (or their parent) wants is to soil or leak MORE than usual! In my experience, the most common reason parents feel that laxatives don't work for their child is that their child has been on an incorrect dose.

The fact is that there is no one dose that is correct for all children. A dose that works for one child may be too much or too little for another child. That’s why I always advise that PEG laxatives be prescribed by the teaspoon and not by the cap, keeping in mind that one cap equals five level teaspoons.  My book describes in detail how to determine the correct dosage for your child.