MiraLAX dosage, forms, and strengths

MiraLAX (polyethylene glycol 3350) is an over-the-counter brand-name laxative taken to relieve occasional constipation. As an osmotic laxative, MiraLAX draws water into the colon to soften stools and make them easier to pass. MiraLAX comes as a powder for a solution either in a bottle or mix-in packets. Before taking a dose, the powder must be thoroughly mixed with a beverage. The standard dosage for adults is one 17-gram dose per day for no more than seven days. However, healthcare professionals may prescribe MiraLAX for long-term treatment of chronic constipation or in larger doses in preparation for bowel procedures. 

MiraLAX forms and strengths

MiraLAX can be purchased as a bottle of powder for solution or individually-packaged mix-in packets. 

• Powder for solution: one capful or one packet (17 g of polyethylene glycol) per day when needed

MiraLAX dosage for adults

Use OTC MiraLAX for occasional constipation or any of the following symptoms:

• No bowel movements for 24 hours

• Few bowel movements over the past three days

• Straining 25% of the time when passing stools

• Hard-to-pass stools

The recommended dosage for adults is one capful or one packet (17 g of PEG 3350) once per day as needed. 

Take MiraLAX for the shortest period possible. MiraLAX should not be used for longer than seven days. After that, get medical advice from a healthcare professional. For chronic constipation, a healthcare provider may prescribe MiraLAX for weeks or months at a time.

Doctors may prescribe MiraLAX to adults in preparation for a bowel procedure such as a colonoscopy. For bowel prep, the dose will be very high and be accompanied by a sheet of detailed instructions.

Check our best MiraLAX prices

Sources: Epocrates and PDR

MiraLAX dosage for children

MiraLAX powder can be used in children as young as infants. For newborns, the safety and effectiveness of PEG 3350 have not yet been established.

Children who weigh less than 44 pounds (20 kg) should not be given MiraLAX packets. Instead, those children should be dosed by weight using MiraLAX powder for solution.

• Standard MiraLAX dosage for children ages 17 and younger who weigh less than 44 pounds (20 kg): 0.2–0.8 g per kg of body weight per day

• Starting MiraLAX dosage for children ages 17 and younger who weigh less than 44 pounds (20 kg): 0.4 g per kg of body weight per day

• Maximum MiraLAX dosage for children ages 17 and younger who weigh less than 44 pounds (20 kg): 17 g per day

• Standard MiraLAX dosage for children ages 17 and younger who weigh more than 44 pounds (20 kg): 17 g per day (one packet or one capful of MiraLAX powder)

Sources: Epocrates and PDR

MiraLAX dosage restrictions

There are no restrictions defined for MiraLAX dosages. No dosage adjustments are necessary for renally impaired or hepatically impaired patients. However, people with kidney disease should first talk to a doctor. 

MiraLAX dosage for pets 

Veterinarians commonly use MiraLAX and generic PEG 3350 to relieve constipation in dogs and cats. Under the advice and supervision of a veterinarian, MiraLAX is considered safe to use.

• Standard MiraLAX dosage for small dogs: ⅛ to ¼ teaspoon of powder mixed into food every 12 hours

• Standard MiraLAX dosage for medium-sized dogs: ¼ to ½ teaspoon of powder mixed into food every 12 hours

• Standard MiraLAX dosage for big dogs: ½ to ¾ teaspoon of powder mixed into food every 12 hours

• Standard MiraLAX dosage for cats: ⅛ to ¼ teaspoon of powder mixed into food every 12 hours

Use MiraLAX in pets for the shortest period possible. Talk to a veterinarian if MiraLAX or PEG 3350 needs to be given to a pet for longer than seven days.

How to take MiraLAX

MiraLAX should be taken once per day for the shortest period possible. Some preparation is required in mixing MiraLAX with a liquid.

• Do not take more than the recommended dosage except under the advice or supervision of a doctor.

• If prescribed by a doctor, follow the doctor’s instructions for dosing.

• One MiraLAX packet contains one dose of MiraLAX.

• When using the bottle top to measure the dose, fill the measuring cap to the top of the white section.

• Dissolve one capful or one packet of MiraLAX powder in a full glass (8 ounces) of water, juice, soda, coffee, or tea. The beverage does not have to be at room temperature.

• Make sure the powder is fully dissolved before swallowing it. If there are any clumps, don’t drink it.

• Take only one dose each day.

• Do not take MiraLAX for longer than seven days. This medicine is not for long-term use.

• It may take two days or longer for this medicine to help you have a bowel movement.

When giving MiraLAX to a child younger than 17, talk to a doctor or other healthcare professional first. Children who weigh less than 44 pounds will require specially-measured doses based on their weight.

For people prescribed MiraLAX for bowel preparation, the dose will be very high. The clinic or healthcare professional will provide a sheet of detailed instructions. Follow all the instructions on the sheet. You may be instructed to drink electrolytes or Gatorade, as well. 

MiraLAX dosage FAQs

How long does it take MiraLAX to work?

MiraLAX should produce a bowel movement one to three days after being taken. For some people, it could be sooner. Harsher laxatives can produce a bowel movement in less than an hour, but they have more uncomfortable side effects. 

How long does MiraLAX stay in your system?

The active ingredient in MiraLAX is PEG 3350. It works by floating around in the intestines and preventing intestinal tissues from reabsorbing water. The extra water makes stools softer and easier to pass. MiraLAX stays in the intestines until it’s excreted out. A very tiny percentage enters the bloodstream, but it doesn’t do anything there. The little bit that enters the bloodstream is gone in about 18 hours. 

What happens if I miss a dose of MiraLAX?

Don’t worry about missing a dose of MiraLAX. It should be taken once per day. If you’re taking it in the morning and forget, take it in the afternoon. Just don’t take two doses in a single day.

How long can you take MiraLAX?

According to the manufacturer, MiraLAX should not be taken for longer than seven days. If there’s still a problem after seven days, talk to a doctor or other healthcare professional. Clinicians may prescribe MiraLAX for up to six months in adults or longer for pediatric patients. If MiraLAX causes diarrhea or loose stools, it’s time to stop taking it.

How do I stop taking MiraLAX?

When used for only a few days, there should be no problems when MiraLAX is discontinued. However, when a doctor prescribes MiraLAX for long-term use, stopping the drug prematurely may bring back constipation and hard stools. Healthcare professionals may taper the MiraLAX dose after long-term use of the drug.

What is the maximum dosage for MiraLAX?

Do not take more than one dose of MiraLAX per day unless instructed to do so by a healthcare professional. 

Can you overdose on MiraLAX?

Only a tiny fraction of the active ingredient in MiraLAX enters the bloodstream, so generally, there’s little to worry about if too much MiraLAX is taken. You may have diarrhea and frequent stools. To put this in perspective, one dose of MiraLAX contains 17 grams of PEG 3350. People who have a colonoscopy may need to drink 227 grams of PEG 3350 the day before. That’s equal to a whole bottle of MiraLAX. At that dosage, the side effects can be very unpleasant but not life-threatening if all instructions are followed.

What interacts with MiraLAX?

MiraLAX does not really enter the bloodstream, so drug interactions are relatively unimportant unless the drug is taken in large doses. The most significant interactions are problems caused by taking MiraLAX with other laxatives, which can cause diarrhea, dehydration, and electrolyte imbalances. 

What happens when you mix MiraLAX and alcohol?

It’s probably not the best idea, but there’s no warning against moderate drinking while taking the recommended dose of MiraLAX for constipation. 

Is it safe to take MiraLAX during pregnancy?

Because so little of the active ingredient enters the bloodstream, MiraLAX is considered safe to take during pregnancy. In fact, healthcare professionals consider it a first-line therapy for constipation in pregnant women.

Is it safe to take MiraLAX while breastfeeding?

Because so little of the active ingredient enters the bloodstream, MiraLAX is considered safe to take while breastfeeding. 

What are the side effects of MiraLAX?

Taken as directed, MiraLAX side effects are minimal. Flatulence and bloating are the most common side effects experienced. MiraLAX can also cause loose stools, frequent stools, or diarrhea, especially in older adults. If that happens, discontinue MiraLAX.

Does MiraLAX have severe side effects?

People taking the correct dose of MiraLAX should not experience severe side effects unless they have pre-existing conditions such as bowel obstruction, appendicitis, perforated bowel, or allergies to PEG 3350. Excessive or prolonged use of MiraLAX can cause electrolyte imbalances, particularly in children. These electrolyte imbalances can result in severe side effects.

Is MiraLAX a stool softener?

MiraLAX is similar to a stool softener. It increases the water content of stools, making them softer and easier to pass. However, it does so by preventing the intestines from reabsorbing water. Laxatives that are considered stool softeners, like Dulcolax Stool Softener (docusate) increase the water content of stools by causing them to absorb more water. They don’t change the way digestive system tissues work. 

What’s the difference between MiraLAX and Dulcolax?

The active ingredient in Dulcolax is bisacodyl, a stimulant laxative that causes intestinal muscles to contract more quickly and strongly, helping to push stools out of the body. Its effects are more immediate, typically resulting in a bowel movement in a few hours. Side effects such as abdominal pain and cramping are more commonly experienced with stimulant laxatives.

Related resources for MiraLAX dosages:

• MiraLAX dosing, Epocrates

• MiraLAX drug information, Food and Drug Administration (FDA)

• MiraLAX website, Bayer Healthcare

• Polyethylene glycol, StatPearls

• Polyethylene glycol 3350 drug summary, Prescriber’s Digital Reference