Miralax (Polyethylene Glycol 3350) - Oral

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What Is Miralax?

Miralax (polyethylene glycol 3350) is an over-the-counter osmotic laxative used to treat constipation. Constipation is characterized as having fewer than three bowel movements a week. Miralax helps treat constipation by allowing the stool to hold more water and pass through the colon. 

Miralax comes in powder form, which must be mixed in a beverage to dissolve. 

Drug Facts

  • Generic Name: Polyethylene glycol 3350
  • Brand Name: Miralax, GaviLAX, GlycoLax
  • Drug Availability: Over the counter
  • Therapeutic Classification: Osmotic laxative
  • Available Generically: Yes
  • Controlled Substance: N/A
  • Administration Route: Oral
  • Active Ingredient: Polyethylene glycol 3350
  • Dosage Form: Powder for solution, packet

What Is Miralax Used For? 

The Food and Drug Administration approved Miralax for short-term use to treat occasional constipation.

How to Take Miralax

To take Miralax, measure the amount of powder in the attached cap. The dose is 17 grams each day. Mix the powder with 8 ounces of a hot or cold beverage, such as water, coffee, or juice. If using individual-dose packets, mix one packet with 8 ounces of liquid. Stir the powder and liquid mixture to dissolve the powder, and then drink it immediately.

Take once a day as needed, and do not take for longer than one week without your healthcare provider’s instruction. You can take it at any time of the day. 


Store Miralax in its original container. Keep dry and at room temperature. 

How Long Does Miralax Take to Work?

It can take Miralax anywhere from six hours to three days to produce a bowel movement.

What Are the Side Effects of Miralax?

This is not a complete list of side effects, and others may occur. A medical professional can advise you on side effects. If you experience other effects, contact your pharmacist or a medical professional. You may report side effects to the FDA at www.fda.gov/medwatch or 1-800-FDA-1088.

Miralax may cause some side effects. These side effects are associated with the way Miralax works to treat constipation. 

Common Side Effects

The most common side effects include:

  • Nausea
  • Gas
  • Abdominal bloating
  • Abdominal cramping

Severe Side Effects

Miralax does not commonly cause severe side effects, but it may cause:

If you experience severe diarrhea or hives, stop taking Miralax and contact your healthcare provider. If you feel that symptoms are severe or life-threatening, call 911 or go to the nearest emergency room for evaluation.

Long-Term Side Effects

If Miralax is taken too often or for too long, it may become habit-forming. Take only as directed. 

Report Side Effects

Miralax may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your provider may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting Program or by phone (1-800-332-1088).

Dosage: How Much Miralax Should I Take?

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The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

For oral dosage form (powder for solution):

For constipation:

  • Adults and children 17 years of age and older—17 grams (g) once a day.
  • Children younger than 17 years of age—Use and dose must be determined by your doctor.


If you are pregnant or nursing, contact your healthcare provider before taking Miralax.

You should also talk to your healthcare provider before using Miralax if you have a history of intestinal blockage.

Missed Dose 

Miralax is taken as needed, and no missed dose instructions are required.

Overdose: What Happens If I Take Too Much Miralax?

Symptoms of a Miralax overdose may include diarrhea, excessive thirst, confusion, or seizures. Dehydration due to diarrhea might occur if you aren’t drinking enough fluids. If you have taken too much Miralax, stop taking the medication and drink plenty of water. 

What Happens If I Take Too Much Miralax?

If you think you or someone else may have overdosed on Miralax, call a healthcare provider or the Poison Control Center (1-800-222-1222).

If someone collapses or isn't breathing after taking Miralax, call 911 immediately.


Drug Content Provided and Reviewed by IBM Micromedex

If your or your child's constipation do not improve within 7 days, or if they become worse, check with your doctor.

What Are Reasons I Shouldn’t Take Miralax?

Do not take Miralax if you are allergic to any of its ingredients or have a known or suspected bowel obstruction. It should also not be used in people with kidney disease unless approved by their healthcare provider.

What Other Medications Interact With Miralax? 

Miralax may have an interaction with a heart medication called digoxin. It is important to talk to your healthcare provider if you take digoxin and want to take Miralax. 

What Medications Are Similar?

Other osmotic laxatives work similarly to Miralax, such as:

  • Magnesium citrate or milk of magnesia
  • Sodium phosphate
  • Lactulose

Miralax generally causes a bowel movement to occur within three days. A magnesium laxative may produce a bowel movement more quickly if needed. 

These drugs are also used to treat constipation, and it is not recommended to take them with Miralax. You should not take these drugs together. Ask your pharmacist or a healthcare provider if you have questions.

Frequently Asked Questions

  • What is Miralax used for?

    Miralax is used to treat constipation, generally described as having fewer than three bowel movements a week.

  • How does Miralax work?

    Miralax works by allowing water in the body to move into the stool in the colon. The water helps the stool soften and move through the colon easier.

  • How long does it take for Miralax to work?

    It can take Miralax anywhere from six hours to three days to produce a bowel movement.

  • How long can I take Miralax?

    Miralax is meant to be taken only for occasional constipation, usually no longer than one week. If you need constipation treatment longer than that, talk to your healthcare provider.

How Can I Stay Healthy While Taking Miralax?

It is important to make sure you’re drinking an adequate amount of water and eating a diet rich in fiber. These strategies can work together to manage constipation and help you have regular bowel movements.

Medical Disclaimer

Verywell Health's drug information is meant for education purposes only and not intended as a replacement for medical advice, diagnosis, or treatment from a healthcare professional. Consult your doctor before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

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  1. U.S. National Library of Medicine. Medline Plus. Polyethylene Glycol 3350. Updated March 15, 2016.

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