How Long Does It Take For Miralax to Work?

Constipation is so bothersome and generally decreases your daily productivity. People who have constipation tends to use Miralax as treatment. But, do you know how long does it take for Miralax to work? Is it instantly right after people use it? Or does it need some time to let the magic happens?

Before that, you should know what kind of drug is Miralax. Miralax is a medication in the form of laxative solution to treat irregular constipation or occasional bowel movements. It adds the water amount in the intestinal tract to provoke the movement of bowel.

People with bowel obstruction, intestinal blockage, and eating disorders like anorexia or bulimia should not use Miralax without doctor’s advice. Or else, you could have dangerous Miralax side effects.

This article will help you in answering the question and in informing some important things about Miralax as well, like the precaution, how to use it, and its side effects, whether or not it really is safe for you.

Before Taking Miralax

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How Long Does It Take For Miralax to Work

Tell your doctor beforehand if you:

  • Have allergy to any drugs
  • Have irritable bowel syndrome, ulcerative colitis, nausea or even vomiting with serious stomach pain, and kidney disease
  • Have had an abrupt change in bowel habits that has lasted for 2 weeks at the very least
  • Pregnant or planning to become pregnant since it’s still unknown if Miralax is harmful to an unborn baby.
  • Breastfeeding a baby because it’s also unknown if Miralax passes into breast milk or if it is harmful to a nursing baby.

About taking Miralax during pregnancy, further information is explained below.

There is no evidence about any animal studies. There are also no controlled data in human pregnancy. Systemic exposure if unavoidable, so clinically significant exposure of the baby is not expected. AU TGA pregnancy category B1: Drugs which have been taken by only a limited number if pregnant women and women of childbearing age, without an increase in the frequency of any malformation or other direct or indirect harmful effects on the baby having been observed. Although, studies in animals have not shown evidence of an increased occurrence of fetal damage. US FDA pregnancy category Not Assigned: The US FDA has amended the pregnancy labeling rule for prescription drug products to require labeling that includes a summary of risk, a discussion of the data supporting that summary, and relevant information to help health care providers make prescribing decisions and counsel women about the use of drugs during pregnancy. Pregnancy categories A, B, C, D, and X are being phased out.” (

In other words, Miralax is not recommended for pregnant women unless it’s needed. The same goes for women with nursing child.

The following will answer the question of how long does it take for Miralax to work. It should produce a bowel movement within 1 to 3 days of using the medication.

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But how long the reaction occurs may vary depending on the individuals, their diets, how much fluid they take, their exercise, and other factors. Miralax is a polyethylene glycol 3350 type of drug which generally causes loose or even watery feces.

Taking Miralax

How Long Does It Take For Miralax to Work
How Long Does It Take For Miralax to Work

Take it precisely as instructed on the label or as prescribed by your doctor.

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Though Miralax is available in drugstore for purchase freely without prescription, still advice from healthcare provider is better because you can be increasing or lessening the amounts without knowing.

For Miralax powder, the dose marks are on the inside of the medicine cap. Measure your dose with it.

Pour the water into 4 to 8 ounces (around 114 to 227 grams) of your preferable hot or cold beverages like juice, water, coffee, tea, or soda. Drink the mixture right away after you stir it. It is not for later consumption.

Do not use Miralax more than once a day. If you’re still constipated after 7 days using the medication, call your doctor immediately. Store Miralax at room temperature and keep it away from heat and moisture.

Miralax Side Effects

Miralax, like all medicines, has side effects which categorized as common and major ones. are including:

Common side effectsAllergic reaction signsStop taking Miralax and call doctor if
  • Gassy, bloating, upset stomach,
  • Belly pain,
  • Stomach cramps,
  • More frequent stools,
  • Dizziness, or
  • Increased sweating.

  • Hives,
  • Rash,
  • Itching,
  • Wheezing,
  • Difficult breathing or talking,
  • Unusual hoarseness,
  • Tightness in the throat or chest,
  • Swelling of your face, tongue, throat, or lips
  • Swollen, red, peeling or blistered skin with or without fever

  • Serious or even bloody diarrhea,
  • Rectal pain or even bleeding,
  • Very bad dizziness or even passing out,
  • Very bad belly pain,
  • Very bad belly bloating or cramping
  • Blood in your feces, or
  • Serious and worsening stomach pain

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Miralax Drug Interactions

how long does it take for miralax powder to work
How Long Does It Take For Miralax to Work

The drug interactions are classified as major, moderate, minor, and unknown. Major means you should avoid the drug combination because the risk is greater than the benefits.

Moderate means the combinations are usually avoided and only prescribed under special circumstances.

Minor means the interaction has minimum risk. And unknown means the interaction has no information available.

The classifications are only a general guideline. It is rather hard to relate certain drug interaction with any individual as there is large number of variables.

In Miralax case, a total of 233 medicines are commonly known to have interactions with this polyethylene glycol 3350 kind of drug. None of major and unknown classifications are there in the list. 232 from 233 drugs are moderate, while one other is minor. The common medications examined in combination with Miralax include acetaminophen (Tylenol), aspirin, ibuprofen, multivitamin, and Vitamin D3 (cholecalciferol).

Miralax, in Comparison

how long does it take for miralax to start working
How Long Does It Take For Miralax to Work

Apparently, in treating constipation and bowel preparation, there is another laxative beside polyethylene glycol 3350 in the brand of Miralax. It is bisacodyl. Let’s take a look at how they differ from each other.

DifferencePolyethylene Glycol 3350 (Miralax)Bisacodyl
PriceMiralax costs USD 1.77 (around IDR 23,500) per unitWhile Bisacodyl costs a bit higher, USD 4.96 (around IDR 65,500) per unit
FormMiralax comes in the form of oral powder for reconstitution which needs to be diluted with certain amount of beveragesWhile Bisacodyl comes in two forms. The one is oral delayed release tablet which taken by mouth and the other is rectal suppository which enters into human system through rectum
Brand NamesOther brands for polyethylene glycol 3350 are including ClearLax, GaviLax, GiaLax, PEG3350, and SunMarkWhile Bisacodyl is available in the brands of Alophen, Bisa-Lax, Carter’s Little Pills, Correctol, Doxidan Tablet, Ducodyl, Dulcolax, and many more
Side EffectsWe’ve learned about Miralax side effects which has common and major one like has been mentioned previously. That's
Gassy, bloating, upset stomach,
Belly pain,
Stomach cramps,
More frequent stools,
Dizziness, or
Increased sweating.
Bisacodyl has them as well. Its side effects include
Abdominal discomfort,
Faintness with therapeutic doses,
Electrolyte and fluid depletion
Diarrhea, and gastric irritation. Bisacodyl rectal administration may cause irritation and burning sensation of the rectal mucosa and mild proctitis
Pregnancy CategoryWhile the risk for Miralax in pregnant women cannot be ruled outBisacodyl has no proven risk in human, and in this case, in pregnant women
Drug InteractionA total of 233 medicines are commonly known to have interactions with Miralax with 232 moderate and 1 minor drug interactionsA total of 282 medicines are commonly known to have interactions with bisacodyl with 281 moderate and 1 minor drug interactions
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Miralax Advantages and Disadvantages

how long does miralax take to work
How Long Does It Take For Miralax to Work

When you get constipation, stool moves slowly through the colon allowing too much water to be removed and eventually makes the stool dry, hard, and difficult to pass. To cure that condition, you need laxative medicines.

However, not all laxatives work similarly with Miralax. Stimulant laxative pills like Senokot, Ex-Lax, and Dulcolax forcefully stimulate your colon nerves.

On the other hand, Miralax works with the water in your body to naturally unblock your system by hydrating, softening, and easing.

These three steps are claimed to be without harsh side effects.

Miralax used effectively to cure constipation. But besides that, it can be used to clean the body before you have to undergo a surgery and clean the digestive tract as well as its main job is to encourage healthy and regular bowel movements.

When compared to other laxatives like bisacodyl brands, Miralax claims to be excellent for a few reasons. First, it appears as an osmotic laxative.

Osmotic laxative means it works with the water within the body to ease and soften stool through the colon. Being works as an osmotic laxative makes Miralax to be more effective and less painful to its users.

Even so, there’s no such thing as perfect medicine in this whole world. Every drug has its own risk and benefits, advantages and disadvantages. The advantages of Miralax have been exposed in three previous paragraphs. It’s time to know what Miralax disadvantages are.

Miralax needs to be dissolved in the right amount of beverages rather than swallow it whole as a pill. It’s okay to do it while you’re at home, but rather difficult when you’re not
Miralax doesn’t work overnight. Through periodic usage, it takes up to four days to have some reaction of bowel movement
Miralax is not recommended to be taken for more than a week. So if you haven’t succeeded within a week, you’ll need to visit your doctor again for other laxative options

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Home Remedies for Constipation

how long does it take for miralax to work colonoscopy
How Long Does It Take For Miralax to Work

While we’re on the subject of constipation, here is some additional information about herbal laxatives which are able to stop constipation and prevent it from happening again.

Spoiler title
They are high in fiber which perfect to encourage healthier bowel movements, improve the overall digestive system health, and remove unwanted toxins from digestive tract.

2. Olive leaves
They help you in relieving your uncomfortable feeling during constipation. They also have oleuropein, an ingredient that helps your bowel movements to be more regular.

3. Flax seeds
They have high amount of Omega 3 and fiber. You can simply use them by adding a tablespoon of them into your meal, like salads, cereals, smoothies, yoghurt, and soups. Grind them first before taking them. Do not have them whole.

4. Cascara sagrada
It is an herbal laxative that works by irritating the colon wall and cause the colon to start contracting. It contains emodin and chrysophanic acid which relieves constipation.

5. Certified organic cloves
They remove unwelcomed organisms from the digestive tract and therefore help you to stop constipation.

6. Senna
It contains hydroxyanthracene glycoside compounds which are the one that help you in curing constipation. It softens the stools and makes passing easy.

7. Slippery elm
It can soothe the digestive system and give detox to your digestive system.

8. Bentonite
It is a clay substance formed from volcanic ash. Bentonite removes unwanted toxins from your colon and carries all those toxins out of your body. Take it with high-fiber food.

9. Turkey rhubarb
It is a very powerful herbal remedy that you must take it with other herbals to reduce the laxative power.

10. Aloe vera
It is known to be used for constipation, skin rashes, internal bleeding, burns, and ulcers. It helps to encourage bowel movements and clean the toxins in the colon.

11. Peppermint
It helps to improve your digestive system health by encouraging the bile production. The bile helps in providing an effect of soothing on your gut lining.

12. Wormseed
Wormseed acts as a purifier for the intestinal tract so it can get rid of constipation fast. It purifies only all the bad bacteria and leave good bacteria intact.


Hopefully, when you reach the bottom of this article, your question of how long does it take for Miralax to work has found the answer.

Nonetheless, all the things that informed in this article should not be used as your decision to take this type of medicine. Because, only health care providers have the knowledge and been on trainings to decide which medicine goes best for which patients.


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