MiraLAX (polyethylene glycol 3350) is an over-the-counter (OTC) drug that’s used to treat occasional constipation. MiraLAX can cause side effects that range from mild to serious. Examples include bloating, gas, and diarrhea.
Specifically, OTC MiraLAX is used in people ages 17 years and older to treat occasional constipation and to soften stool. If you want to use MiraLAX in children ages 16 years or younger, talk with their doctor.
MiraLAX comes as a powder that you mix into 8 ounces of a beverage (such as water, juice, coffee, or tea) before drinking.
Keep reading to learn about the common, mild, and serious side effects that MiraLAX can cause. For a general overview of the drug, including details about its uses, see this article.
Some people may experience mild to serious side effects while taking OTC MiraLAX. Examples of the drug’s commonly reported side effects include:
- nausea*
- gas
- bloating
- cramping
- diarrhea*
* To learn more about this side effect, see the “Side effects explained” section.
Mild side effects have been reported with OTC MiraLAX. These include:
- abdominal pain
- bloating
- cramping
- diarrhea*
- gas
- frequent bowel movements
- nausea*
In most cases, the side effects of MiraLAX should not last long and will go away as your body becomes used to the drug. And some side effects may be easily managed by adjusting your dose or decreasing how many times per week you take MiraLAX. But if you have symptoms that are ongoing or bothersome, talk with your doctor or pharmacist.
MiraLAX may cause mild side effects other than those listed above. See the drug’s prescribing information for details.
* To learn more about this side effect, see the “Side effects explained” section.
Serious side effects have been reported with OTC MiraLAX, such as dehydration. (To learn more about this side effect, see the “Side effects explained” section.)
If you develop serious side effects while taking MiraLAX, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.
Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with MiraLAX, visit MedWatch.
Allergic reactionFor some people, OTC MiraLAX can cause an allergic reaction. In general, symptoms of an allergic reaction can be mild or serious.
What might help
If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms and can determine whether you should keep taking MiraLAX.
If you have symptoms of a severe allergic reaction, such as swelling or difficulty breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.
If your doctor confirms you’ve had a serious allergic reaction to MiraLAX, they may have you try a different drug to treat constipation.
Get answers to some frequently asked questions about OTC MiraLAX’s side effects.
Should I avoid or limit certain foods to reduce side effects from MiraLAX?
You don’t have to avoid any specific foods while taking MiraLAX to help prevent side effects. But you may want to limit foods or beverages that can lead to constipation, such as:
- cheese, butter, and ice cream
- fried foods
- fatty meats
- sugary foods, including desserts such as cookies or cakes
- alcohol
To help relieve constipation, eat high fiber fruits and vegetables, whole grains, and lean meats. Also, drinking plenty of water instead of juice or soda helps MiraLAX keep your stool soft.
If you need help with dietary changes, consider talking with a dietitian. Some health insurance companies provide access to a dietitian through their health plans.
Does MiraLAX cause any long-term side effects?
It’s possible. Long-term use of OTC MiraLAX may cause certain problems, including:
- frequent diarrhea
- dehydration
- low levels of certain minerals in the blood (potassium, sodium, and magnesium)
If you develop blood in your stool or constipation symptoms (such as bloating or abdominal pain) that become worse while taking MiraLAX, stop taking it and contact your doctor right away. These symptoms may be from a serious condition.
If you’d like to use MiraLAX for longer than 1 week, you should first talk with your doctor. They can monitor for potential side effects and ensure you use it safely.
Does MiraLAX cause any specific side effects in children?
However, problems with MiraLAX reported to the FDA MedWatch program were summarized in a
- seizures
- anger
- sensory problems
- shaking or tremors
- anxiety
- depression
- changes in mood
The authors of this summary pointed out that no reports of these behavioral side effects occur in studies of MiraLAX.
Because MedWatch reports rely on individual accounts rather than structured research, it’s not clear whether these side effects are from MiraLAX use or another cause. But as a result of these reports, the FDA is doing new studies focused on MiraLAX use in children.
If you’re concerned about your child using MiraLAX and the side effects it could cause, talk with your child’s doctor. Also, keep in mind that using MiraLAX in children ages 16 years and younger requires a doctor’s supervision.
Learn more about some of the side effects that OTC MiraLAX may cause.
Diarrhea
Diarrhea was a common side effect reported in studies of MiraLAX. Factors that can increase the risk of diarrhea when taking this drug include:
- taking more than the recommended dose of MiraLAX
- being ages 65 years or older
What might help
If you develop diarrhea while using MiraLAX, stop taking it and try the following:
- drink plenty of water
- eat bland foods such as bananas, crackers, and broth
Before you begin taking MiraLAX again, you may want to reduce your dose or limit how many times you take it in a week. Talk with your doctor or pharmacist about what’s best for your specific situation.
If you notice blood in your stool or have a fever with diarrhea, seek urgent medical care. These could be symptoms of a severe infection or dehydration.
Nausea
Nausea was a common side effect reported in studies of MiraLAX. Nausea may cause symptoms such as:
- feeling like you may vomit
- upset or “churning” stomach
Factors that can increase the risk of nausea when taking this drug include:
- not drinking enough water
- you have had irritable bowel syndrome, heartburn, or hiatal hernia before
- eating acidic, greasy, or spicy foods
- taking other medications that can cause nausea (such as aspirin or ibuprofen)
- taking more than the recommended dose of MiraLAX
What might help
If you have nausea while taking MiraLAX, you can try:
- increasing the amount of water you drink with and after your dose
- eating bland foods and taking your dose after a small meal
- remaining upright for at least 1 to 2 hours after taking your dose
If your nausea continues, talk with your doctor or pharmacist. They may recommend that you adjust your dose or try a different treatment.
Dehydration
Dehydration was an uncommon side effect reported in studies of MiraLAX. Dehydration may cause symptoms such as:
- muscle cramps or spasms
- dark urine
- dizziness
- thirst
- dry mouth
- fatigue
- confusion
Factors that can increase the risk of dehydration when taking this drug include:
- having severe diarrhea
- being ages 65 years or older
- using prescription or OTC diuretics (water pills)
- drinking excessive alcohol or caffeinated beverages
- taking more than the recommended dose of MiraLAX
What might help
If you have symptoms of mild dehydration, stop taking MiraLAX and try:
- drinking plenty of water or a rehydration drink containing electrolytes, such as a low-sugar sports drinks
- taking rest
If you develop symptoms of severe dehydration, such as lethargy or fever, or are unable to urinate, seek emergency medical care. These symptoms have the potential to be life threatening.
Below is important information you should consider before taking OTC MiraLAX.
Warnings
MiraLAX can sometimes cause harmful effects in people who have certain conditions. This is known as a drug-condition interaction. Other factors may also affect whether MiraLAX is a good treatment option for you.
Talk with your doctor or pharmacist about your health history before you take MiraLAX. Be sure to tell them if any of the following factors apply to you:
- change in bowel movements over the last 2 weeks
- past bowel obstruction or rectal bleeding
- have had irritable bowel syndrome, heartburn, or hiatal hernia before
- previous allergic reaction to MiraLAX
- pregnancy
- breastfeeding
- alcohol consumption
Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.