Does Miralax Go Bad

In this brief article, we will answer the question “does Miralax go bad?”, and will be discussing the uses, effects, dosage, and side effects of this medication. 

Does Miralax Go Bad?

Miralax that is a week, month, or even a year past its expiration date doesn’t necessarily go bad and can still be used; it just loses its original potency and effectiveness. However, using Miralax that has expired is not recommended. 

Most medications, if stored under appropriate conditions, remain about 70 to 80 percent potent for as many as two years after their expiration date, even if their container has been opened. The pharmaceutical product shelf life, also referred as the expiration date, is the time period during which the product is expected to retain its identity, purity, quality, and strength when properly stored as specified in the container label.1 Performance of the drug product beyond the manufacturer set shelf

life has been a subject of study over the past several decades. Studies have shown that many drug products retain their shelf life quality characteristics such as potency and efficacy, several years beyond the expiration date if stored properly (1).

How Can You Prevent Miralax From Going Bad?

Since Miralax is a powder available in bottle form as well as single-serve packets, they must be stored at room temperature away from direct light, humidity, and moisture. There are several mechanisms by which a drug product degrades. The chemical pathways include degradation of the active pharmaceutical ingredient by the environmental conditions such as temperature, humidity, oxygen, free radicals, photolytic (by light). Physical changes involve changes in crystallinity, solubility and dissolution of the active ingredient during storage. Therefore, storage conditions are determinant (1). 

Medicine stored in a cool, dry place can last for years without losing its effectiveness. 

What is Miralax Used For?

Miralax is a gluten-free, sugar-free, and preservative-free medication generally used for the short-term treatment (and in certain cases long-term) of chronic constipation. It can also be used for colonoscopy bowel preparation. (PEG) is a product with industrial and pharmaceutical uses. Since many PEG compounds are hydrophilic, industrially, they are utilized in cosmetic products as surfactants, emulsifiers, cleansing agents,humectants, and skin conditioners.As a medication, PEG is a part of the laxative class. FDA-approved indications include the treatment of constipation in patients 17 years of age and older (2).

How Does Miralax Work?

The active ingredients in Miralax are osmotic-type laxatives, including GlycoLax, GoLYTELY, and polyethylene glycol (PEG). 

These compounds act by retaining water in the stool that softens it, and also by increasing the frequency of bowel movements. PEG is soluble in water and is not reabsorbed in the gastrointestinal tract as a medication. PEG forms hydrogen bonds with water molecules. For this reason, it can prevent the reabsorption of water, which causes water retention in the stool and increases the osmotic pressure (2). Miralax uses the body’s own water to hydrate, loosen and ease stools, naturally unblocking the digestive tract.

In most individuals, Miralax results in a bowel movement within one to three days after taking it.

How Long Does A Miralax Solution Last?

The unused or remaining solution of Miralax can be kept in the refrigerator for up to 48 hours, after which it must be discarded. Do not freeze the solution. 

When Should You Take Miralax?

There is no specific time of the day when you should take Miralax.

Simply start taking the medication at the earliest signs of constipation, and continue using it until it provides relief. For adult constipation, Miralax is mixed in 8 ounces of liquid and taken once daily. The fluid can include water, juice, tea, coffee, or soda (2).

You should not use Miralax for over seven days. If you need to take a laxative for more than a week for relief, discontinue its use and consult a doctor.

How Do You Use Miralax?

Individuals aged 17 and above should take no more than 17 grams of Miralax powder. Use the Miralax bottle top to accurately measure 17 grams of powder as indicated by a line inside the cap. Dissolve the powder in four to eight ounces of any cold, hot, or normal liquid.

For children aged 16 or below, consult a doctor for the appropriate dosage; single-dose packets might be a more reasonable option for them. Some studies indicate that it is also safe for children greater than two years of age, when taken for fecal impaction, the dose is 1 to 1.5 g/kg/day for 3 to 6 days, with a maximum of 6 consecutive days. In more chronic constipation cases, the initial dosing is 0.4 mg/kg/day orally; then, maintenance dosing is 0.2 to 0.8mg/kg/day adjusted to response. The recommendation is to continue for at least two months and discontinue gradually once symptoms resolve for at least a month (2).

Does Miralax Have Any Side Effects?

Miralax does not have any serious side effects, such as bloating, abdominal cramping, or an urgency to go to the bathroom. It provides gentle and appropriate relief from constipation. However, for sensitive people, common side effects include flatulence, nausea, stomach cramps, diarrhea, swollen abdomen, and rectal hemorrhage (2).

In addition,However, you might experience watery, loose, and more frequent stools while taking the medication. 

Can You Overdose on Miralax? 

Symptoms of a Miralax overdose include diarrhea and increased thirst.

As mentioned, Miralax must not be taken more than once daily, and also not longer than seven days, or the length prescribed by your doctor. It is contraindicated in patients with known or suspected bowel obstruction, appendicitis, inflamed bowel disease,perforated bowel, and hypersensitivity to polyethylene glycol, any component of the formulation (2).

Is Miralax Addictive?

Miralax does not affect muscles and nerves of the digestive tract, hence it is not habit-forming or addictive. It has been safely used to treat chronic constipation in children and adults for years without any complaints of dependency. 

What Is A Good Substitute For Miralax?

If you’re reluctant to take medication for constipation, here are some natural substitutes (3):

  • lactulose (a non-absorbable sugar)
  • magnesium hydroxide (also known as Milk of Magnesia)
  • senna (a herbal extract that aids bowel movements)
  • mineral oil
  • warm water enemas
  • psyllium 

How Can You Avoid Getting Constipation?

Here are a few things you can do for cleansing your digestive system and having regular bowel movements (3):

  • Increase the amount of fiber in your diet
  • Consume less of low-fiber foods
  • Add more liquid to your diet, preferably water and fresh juices
  • Reduce stress
  • Don’t delay a bathroom visit; go as soon as you feel the urge
  • Schedule toileting after meals


In this brief article, we answered the question “does Miralax go bad?” and discussed the uses, effects, dosage, and side effects of this medication. 

If you have any more questions or comments please let us know.


  1. Khan, Saeed R., et al. United States Food and Drug Administration and Department of Defense Shelf‐Life Extension Program of Pharmaceutical Products: Progress and Promise. J Pharmaceut Sci, 2014, 103, 1331-1336.
  2. Dabaja, Amani, Ali Dabaja, and Malak Abbas. The Elderly at Risk. Am J Ther. Polyethylene Glycol. StatPearls, 2021.
  3. Mounsey, Anne, Meghan F. Raleigh, and Anthony Wilson. Management of constipation in older adults. Am fam phys, 2015, 92, 500-504.