Key takeaways

  • MiraLAX contains polyethylene glycol 3350 (PEG 3350), an osmotic laxative that draws water into your colon to soften stool and may naturally stimulate bowel movements within 1 to 3 days.
  • Common side effects include diarrhea, gas, nausea, stomach pain, and bloating. Serious but less common risks include dehydration and allergic reactions.
  • MiraLAX is intended for short-term use (up to 7 days) in adults and adolescents ages 17 years and older. If you are still constipated after 7 days of MiraLAX use, contact a doctor.

MiraLAX is a brand-name, over-the-counter (OTC) medication used to treat occasional constipation. It contains the active ingredient polyethylene glycol 3350 (PEG 3350) and belongs to a group of drugs known as osmotic laxatives.

MiraLAX comes as a powder that you mix with a liquid before taking it. Because it is an OTC product, you can purchase MiraLAX without a doctor’s prescription.

The primary use of MiraLAX is to treat occasional constipation in adults and older adolescents ages 17 years and older. Constipation occurs when bowel movements become difficult to pass or occur less often than usual. It can leave you feeling bloated, heavy, or uncomfortable.

MiraLAX is intended for short-term use. If you have frequent episodes of constipation or laxatives like MiraLAX are ineffective at providing relief, talk with a doctor. (A gastroenterologist is the primary medical specialist for diagnosing and treating chronic constipation.)

MiraLAX works with the water that is already in your body. When you take MiraLAX, it travels through your digestive system without being absorbed into your bloodstream. Instead, it holds onto water and brings it into your colon. This extra water softens your stool and increases the frequency of your bowel movements.

Softening the stool makes it much easier to pass, which helps reduce the straining and discomfort often associated with being “backed up.”

Because it works naturally with water, MiraLAX usually provides more comfortable relief from constipation without causing sudden urgency or cramping that may occur with other constipation remedies that force the muscles in your gut to squeeze.

How long does it take to work?

MiraLAX doesn’t usually cause a bowel movement immediately after you take it. Most people find that it helps produce a bowel movement within 1 to 3 days of the first dose.

Getting the right dose of MiraLAX is important for the medication to work safely and effectively. According to its label, the standard dose of MiraLAX for adults and children ages 17 years and older is 17 grams (g) of powder per day.

To make it easy to measure, MiraLAX packaging often includes a built-in measuring tool. MiraLAX bottles have a cap that doubles as a measuring cup. You should fill the cap to the indicated line, which marks exactly 17 g.

If you are using single-serve packets of MiraLAX, one packet equals one dose.

You should not take more than one dose of MiraLAX in a 24-hour period unless a doctor tells you to do so.

MiraLAX dosage for children

The Food and Drug Administration (FDA) has approved MiraLAX for use in older children (adolescents) ages 17 years and older. The dosage for these adolescents is the same as for adults.

For children under 16 years of age, ask a doctor before giving them any amount of MiraLAX.

MiraLAX is a powder that must be mixed with a liquid before you take it.

Follow these 3 easy steps to prepare and take a daily dose of MiraLAX:

  1. Measure the powder using the bottle cap, or use a single-serve packet.
  2. Stir the powder into 4 to 8 ounces of a beverage (water, juice, soda, coffee, or tea). It can be served cold, hot, or at room temperature. Stir the mixture well until the powder is completely dissolved.
  3. Once the liquid is clear and there are no clumps left, drink the entire glass. It is important not to sip it over a long period; drink the full dose at once to make sure you get the proper amount of medication.

Timing

You can take MiraLAX at any time of the day. However, it may be best to take it in the morning. That way, if it causes a bowel movement, you’ll be able to go to the bathroom during the day rather than during the night.

How often can you take MiraLAX?

You should only take MiraLAX once a day, unless your doctor gives you different instructions.

Do not take MiraLAX for more than 7 days without talking with your doctor. Your doctor may want to evaluate the cause of your constipation. Your doctor may find that you need other treatments.

Taking MiraLAX with food

You can take MiraLAX with or without food.

Most people can take MiraLAX without having any major issues. However, like all medications, MiraLAX can sometimes cause mild side effects as your body adjusts to it.

The most common side effects of MiraLAX involve the digestive system and may include:

  • gas
  • bloating
  • a slightly upset stomach

Some people feel a bit of “rumbling” in their abdomen as MiraLAX begins to work. And because MiraLAX brings water into the colon, you might also experience loose or watery stools. If you find that your stools are becoming too frequent or too liquid, stop using MiraLAX and talk with a healthcare professional.

While serious side effects of MiraLAX are rare, they can happen. It is important to monitor how your body reacts to MiraLAX, especially during the first few days of use.

Allergic reaction

One serious concern is a severe allergic reaction. If you notice a skin rash, hives, or itching after taking MiraLAX, stop using it immediately.

Signs and symptoms of a more severe allergic reaction include:

  • swelling of the face, lips, or tongue
  • trouble breathing

Severe diarrhea

Another serious side effect is severe diarrhea. If you have diarrhea that does not stop, it can lead to dehydration, which is a loss of too much body water. If you feel dizzy, extremely thirsty, or notice that your heart is beating faster than normal, call a doctor right away.

Call 911 or your local emergency number immediately if your symptoms feel life threatening or if you think you’re having a medical emergency.

Before you start any new medication, you should consider how it might interact with other things you are taking. An interaction occurs when two substances affect each other, altering how they work or increasing the risk of side effects.

MiraLAX is generally safe because it is not absorbed into the body. But it can affect how other oral medications work.

MiraLAX speeds up the movement of things through your intestines, so it might prevent other medications from being fully absorbed and make them less effective.

If you are taking any prescription medications — especially those for heart health, seizures, or high blood pressure — it’s a good idea to talk with a doctor or pharmacist before taking MiraLAX.

Before taking MiraLAX, talk with your doctor about your medical history. There are certain situations when you should be extra careful or avoid MiraLAX entirely, including:

  • Kidney disease: Although it’s not common, MiraLAX and other laxatives can cause electrolyte imbalances. This problem can be worse in people with kidney disease.
  • Stomach problems: If you are experiencing nausea, vomiting, or stomach pain, do not take a laxative. These could be signs of a more serious medical condition, such as a bowel obstruction.
  • Irritable bowel syndrome (IBS): MiraLAX and other laxatives may worsen some symptoms of IBS.
  • Difficulty swallowing.
  • Previous allergic reaction to polyethylene glycol or other laxatives.
  • Pregnancy or breastfeeding.

If any of these apply to you, consult a doctor before taking MiraLAX.

Finally, do not take MiraLAX for more than 7 days. If you still need a laxative after a week, call a doctor.

Taking more than the recommended dose of MiraLAX can lead to uncomfortable and potentially dangerous symptoms.

An “overdose” of a laxative usually results in an extreme version of its intended effect. If you take too much MiraLAX, the most likely result is severe diarrhea. This can quickly lead to dehydration and a loss of electrolytes (minerals like salt and potassium that your body needs to function).

Overdose symptoms

Symptoms of a MiraLAX overdose can include:

  • intense stomach cramping
  • bloating
  • stomach pain
  • nausea
  • excessive diarrhea
  • dehydration
  • electrolyte imbalances
  • thirst
  • feeling very weak or faint

What to do in case of overdose

If you think you’ve taken too much MiraLAX, call a doctor or seek guidance from America’s Poison Centers at 800-222-1222 or visit its Poison Help website. But if your symptoms are severe, call 911 or go to the nearest emergency room right away.

Note: Always store MiraLAX out of the reach of children to prevent accidental ingestion.

Yes, MiraLAX is a laxative. It’s called an osmotic laxative. This means it works by drawing water into the colon. The water softens the stool and may naturally stimulate the colon to contract. These actions help ease bowel movements.

MiraLAX is classified as an osmotic laxative, not a stool softener. However, both products do soften the stool. Osmotic laxatives do this by drawing water into the colon (large intestine). Stool softeners do it by drawing water into the stool itself.

Unlike “stimulant” laxatives that cause the colon to cramp and force a bowel movement, MiraLAX is an osmotic laxative. This means it generally provides a more predictable, gentler experience.

Most people who take MiraLAX find they have more control and do not experience the sudden, painful “run to the bathroom” feeling that may occur with other constipation treatments.

Yes, you can take MiraLAX with fiber. Many people take fiber daily to prevent constipation and for general digestive health. Fiber products are usually the first choice for preventing and treating constipation.

When fiber isn’t enough to prevent or treat constipation, MiraLAX may also be taken until constipation goes away.

MiraLAX and other over-the-counter (OTC) laxatives are usually only recommended for short-term use, up to a week.

If your constipation lasts longer than a week, you should contact a doctor. Your doctor may want to evaluate the cause of your constipation. Depending on the cause, your doctor may recommend long-term use of MiraLAX or other treatments.

No. MiraLAX is only available as an over-the-counter (nonprescription) formulation.

In summary, here are a few important MiraLAX safety tips to remember:

  • Measure the 17-gram dose carefully, dissolve it completely in 4 to 8 ounces of your favorite drink, and only take it once per day.
  • While mild gas or bloating can happen, serious side effects are rare. Call a doctor immediately if you have severe diarrhea or symptoms of a severe allergic reaction after taking MiraLAX.
  • Always follow the 7-day rule: If your constipation lasts longer than 7 days after taking MiraLAX, see a doctor.

By following the instructions on the MiraLAX product label and listening to your body, you can safely achieve the constipation relief you need.

Disclaimer: While Medical News Today strives for factual, comprehensive, and current information, this article is not a substitute for a licensed healthcare professional’s expertise. Always consult a doctor before taking or discontinuing any medication. Drug information is subject to change and may not cover all uses, directions, precautions, warnings, interactions, reactions, or adverse effects. The lack of a warning does not guarantee a drug’s safety, effectiveness, or appropriateness for all patients or specific uses. Learn more about our approach to content integrity.