What Is MiraLAX?

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MiraLAX is the brand name for the generic drug polyethylene glycol 3350, a laxative used to treat occasional constipation.

The drug works by bringing water into the bowels, which helps keep the digestive system regular. Stool becomes softer when the bowels retain water.

MiraLAX typically relieves constipation in one to three days.

Braintree Laboratories first introduced MiraLAX in 1999, and it was available only by prescription until 2006, when the Food and Drug Administration (FDA) concluded that polyethylene glycol 3350 was safe and effective, and could be sold over the counter (OTC) instead of by prescription.

In 2009, the FDA approved additional generic forms of polyethylene glycol 3350 DA, sold under the name polyethylene glycol 3350, or PEG 3350.

A study published in the American Journal of Gastroenterology in 2013 reported that polyethylene glycol 3350 plus electrolytes was an effective treatment for constipation for adults with a particular type of irritable bowel syndrome with constipation (sometimes called IBS-C). 

IBS-C is a gastrointestinal disorder that causes pain or discomfort because of changes in the frequency or consistency of bowel movements.

That year, Schering-Plough Corporation entered into a licensing agreement with Braintree to market nonprescription MiraLAX as a treatment for occasional constipation, and the FDA granted Schering-Plough three years of exclusivity for the OTC drug.

Some pediatricians have expressed concern that MiraLAX is routinely given to children for lengthy periods of time, though it has never been approved by the FDA for use by children younger than 17 years, and the long-term effects of use in children have not been studied.

A 2009 meeting of the FDA's Drug Safety Oversight Board discussed reports of metabolic acidosis (high levels of acid in the blood) and psychiatric events including seizures, tremors, and aggressive behaviors among children using polyethylene glycol laxatives such as MiraLAX.


MiraLAX Warnings

Don't take MiraLAX if you have kidney disease or an allergy to polyethylene glycol.

Polyethylene glycol 3350 may be habit-forming. If you use MiraLAX too often or for a prolonged period of time, you could become dependent on laxatives.

Using it often and for an extended time also could result in an electrolyte imbalance.

People who have or may have a bowel obstruction (blockage in the intestine) should not take MiraLAX. Have your doctor rule out this condition before you use MiraLAX.

Symptoms of a bowel obstruction include nausea, vomiting, stomach pain, and a distended belly.

Before taking MiraLAX, be sure to talk to your doctor if you have any of the following:

  • Nausea or vomiting
  • Abdominal pain
  • A sudden change in bowel habits that lasts more than two weeks
  • Irritable bowel syndrome (IBS)

Your doctor should also know if you have or have ever had a bowel obstruction or if you have symptoms of bowel obstruction, such as an upset stomach, vomiting, and stomach pain.

It's also important talk to your doctor before using MiraLAX if you are pregnant, may become pregnant, or are breastfeeding.

If you experience rectal bleeding, nausea, or abdominal pain that gets progressively worse, or if your constipation is not better after taking MiraLAX for one week, talk to your doctor right away. These could be signs of a more serious condition.

Children younger than 17 years old should take MiraLAX only under the direction of their pediatrician.

MiraLAX Side Effects

What Are the Most Common and Serious Side Effects of MiraLAX?

Common side effects of MiraLAX include:

  • Watery loose stools
  • Gas
  • Nausea
  • Bloating
  • Cramping

More serious side effects could occur. If you have any of these side effects, stop taking MiraLAX and call your doctor:

  • Diarrhea
  • Hives

MiraLAX Interactions


Many prescription drugs and OTC products can interact with MiraLAX and affect how either medication works. Sometimes this can be dangerous or life-threatening.

Interactions also can happen between medications and other products, like herbal remedies, vitamins, and nutritional supplements.

Researchers have not found any specific drug interactions with MiraLAX, but it's always important to let your doctor know about all drugs you are taking, including any illegal or recreational drugs, OTC medications, herbs, or dietary supplements.

While taking MiraLAX, it's important to eat a well-balanced diet that includes high-fiber foods such as unprocessed bran and whole-grain bread as well as fresh fruits and vegetables.

It's also important to drink plenty of fluids and get regular physical activity.

MiraLAX Dosage


MiraLAX comes as a powder, which you dissolve in liquid and drink.

You can mix MiraLAX with water, juice, soda, coffee, or tea, and the liquid can be cold, hot, or room temperature.

The MiraLAX bottle cap is marked to hold 17 grams of the laxative when filled to the indicated line. Adults and teenagers 17 and older can use the bottle cap to measure the powder.


Don't use MiraLAX more than once a day, and don't use it for longer than one week unless your doctor recommends it.

If MiraLAX doesn't relieve your constipation after seven days, talk to your doctor.

MiraLAX Overdose

Don't take more than the recommended amount of MiraLAX.

It's also important not to take it more than once a day, or for longer than the length of time your doctor recommends.

Symptoms of a MiraLAX overdose may include:

  • Diarrhea
  • Increased thirst
  • Confusion
  • Seizure

If you or someone else has symptoms of an overdose, call a poison control center at 1-800-222-1222. If someone collapses or isn't breathing after taking MiraLAX, call 911.

Missed Dose of MiraLAX

It may take MiraLAX up to four days to work.

If you stop taking it before it produces a bowel movement, you may remain constipated. Take this medication as recommended.

MiraLax FAQ

Q: Can you tell me if the laxative Miralax, and the generics like it, is a natural laxative or one that would become habit forming?

A: Miralax is a laxative made up of the active ingredient polyethylene glycol 3350 (PEG) and has been studied and proven safe and effective, in more high-quality clinical trials, than any other laxative. It is not considered a natural laxative, but that does not make it a bad thing either. PEG is used in a variety of different ways in many medications such as laxatives, bowel preps used for colonoscopy, IV medications, and skin creams. It has an extremely low risk of toxicity and can be used for prolonged periods of time without the risk of becoming habit forming either psychologically or physically. Here is some information on the product Miralax that may be able to answer some of your questions: http://www.everydayhealth.com/drugs/miralax Lori Poulin, PharmD

Q: Is there any interaction between Miralax and lisinopril, Zocor, Plavix, aspirin, or HCTZ?

A: Although there are some interactions between several of the drugs you are currently on, such as Plavix and aspirin, or lisinopril and hydrochlorothiazide, these medications are often prescribed together because the benefits outweigh the risks. The only caution with adding Miralax (Polyethylene glycol 3350) to your medication regimen is that chronic use of Miralax and hydrochlorothiazide can cause significant losses of fluid and electrolytes, including sodium, potassium, magnesium and zinc. In general, laxatives should only be used on a short-term basis in recommended dosages under the supervision of your doctor. When using Miralax with hydrochlorothiazide, be sure to contact your physician if you experience signs and symptoms of fluid and electrolyte depletion such as dizziness, lightheadedness, dry mouth, thirst, fatigue, weakness, lethargy, muscle cramps, decreased urination, fainting upon standing, or a fast heart rate. A more natural way to promote bowel regularity is regular exercise and a fiber-rich diet. You can also consider using a bulk-forming laxative instead if you require long term constipation relief.

Q: I'm taking generic MiraLax. Does it affect absorption of any other drugs you are on? And when should you take it? I'm taking multiple drugs, and the last one, which is propranolol, is taken around 11 p.m. Then I'll wait a half hour to take the MiraLax or vice versa. Does it affect what it does?

A: When combining MiraLax (polyethylene glycol) with propranolol (Inderal), there are no significant interactions found for these selected drugs. Caution always advised with multiple medications. Therefore, MiraLax does not appear to affect the absorption of propranolol and it should not matter when you take either one. Check with your health care provider before making any changes to prescribed medications. Lowell Sterler, RPh

Q: Why has Miralax been recalled?

A: Some of the over the counter MiraLAX products have been recalled. The recall by Schering-Plough is for the 17.9 oz bottle as well as the 19.9 oz bottle. The caps on these bottles may not fit properly. There is concern that this could be a choking risk to children as well as allow contamination of the contents of the bottle. If you are using or have used MiraLAX do not be alarmed; there are no reported problems with the actual medication. Many generic forms of MiraLAX bottles are still available and the MiraLAX packets have not been recalled. Burton Dunaway, PharmD

Q: A specialist I saw a couple of years ago said to take 1 cup CoLyte when my IBS constipation symptoms start acting up. Do you need a prescription for it? Or is there anything similar to buy over the counter?

A: The active ingredient in Colyte is PEG 3350. This is the same ingredient found in Miralax, now over the counter. You can also find helpful information on Miralax at http://www.everydayhealth.com/drugs/miralax. Matt Curley, PharmD

Q: Is it okay to use Miralax for my 8-month-old baby?

A: Miralax (polyethylene glycol [PEG]) is not indicated nor has it been studied in children younger than 18 months. It is not advisable to give this to infants or children under age 17. If your child has a history of occasional or chronic constipation, it is best to consult with a physician. I have provided a link about constipation in children that may be helpful. http://www.everydayhealth.com/digestive-health/kids-and-constipation.aspx. Lori Mendoza, PharmD

Q: Can Miralax be taken daily?

A: Miralax (Polyethylene Glycol 3350) is a laxative that increases the amount of water in the intestines. Miralax is used to treat occasional constipation and irregular bowel movements. Measure the dose of Miralax with the medicine cap on the bottle. This cap should contain dose marks on the inside of it. Pour the powder into 4 to 8 ounces of a cold or hot liquid such as water, juice, soda, coffee, or tea and use as prescribed. Miralax can produce bowels movements within 1-3 days of the initial dose. Do not use Miralax for more than 7 days without consulting the doctor. Call your doctor if you are still constipated or irregular after using this medication for 7 days in a row. Frequent or excessive use without the doctor's approval can upset the body's chemical balance and lead to dependence on laxatives. Common side effects of Miralax can include bloating and gas, upset stomach, and dizziness. Miralax can cause loose or watery stools. Some medications may interact with the Miralax. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor. Miralax is available as a prescription or over-the-counter. Consult with the doctor if you think you need to use the Miralax on a daily basis. The healthcare provider can give you guidance based on your health status and medications. Kimberly Hotz, PharmD

Q: My 3 1/2 year old granddaughter has been on Miralax since she was 9 months old. It worries me that she may have health problems later on due to this chemical being in her body so long. Can you tell me if this is okay?

A: Miralax (polyethylene glycol) is an osmotic laxative used to treat constipation. Miralax works by bringing water into the stool which softens the stool and helps it to be passed. Miralax is approved by the U.S. Food and Drug Administration (FDA) for occasional constipation. According to the package information, Miralax should be used for two weeks or less or as directed by a physician. Prolonged use of Miralax has the potential to cause electrolyte abnormalities and/or a dependence on laxatives (not being able to have a bowel movement without a laxative). Consult with the pediatrician to discuss the risks and benefits of prolonged Miralax use. Miralax should be dissolved in 8 ounces of water or juice before taking. Notify the child's doctor if she has cramping, if constipation gets worse, or if there is bloating, nausea or diarrhea. Some ways to help prevent constipation include drinking plenty of fluids, eating a high fiber diet, and getting plenty of exercise. Fiber is found in fruits, vegetables, whole grains and beans. It is important to discuss any adverse effects from medications with the doctor. For more specific information, consult with your doctor or pharmacist for guidance based on your health status and current medications, particularly before taking any action. Laura Cable, PharmD