Is it effective to take Metamucil (psyllium) in the morning and Miralax (polyethylene glycol) at night?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: April 28, 2025View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

From the Guidelines

Taking Metamucil in the morning and MiraLAX at night can be an effective combination for managing constipation, as recommended by the American Gastroenterological Association and American College of Gastroenterology clinical practice guideline 1.

Key Considerations

  • Metamucil, a psyllium fiber supplement, is conditionally recommended for adults with chronic idiopathic constipation (CIC) due to its effectiveness in adding bulk to stool and promoting regular bowel movements 1.
  • MiraLAX, a polyethylene glycol (PEG) osmotic laxative, is strongly recommended for adults with CIC, as it has been shown to be effective in softening stool and promoting bowel movements 1.

Dosage and Administration

  • Take 1 tablespoon of Metamucil powder mixed in 8 ounces of water in the morning, or as directed on the package.
  • Take 17 grams (about 1 heaping tablespoon) of MiraLAX dissolved in 8 ounces of water at night, as it typically takes 24-72 hours to work.

Important Precautions

  • Always drink plenty of water with both products to prevent dehydration and ensure effectiveness.
  • Discontinue use if you experience abdominal pain, nausea, or other concerning symptoms.
  • Be aware of potential side effects, such as flatulence and abdominal distension, which are commonly observed with fiber and PEG use 1.

Monitoring and Follow-up

  • Regularly assess your bowel movements and adjust the dosage or combination of products as needed.
  • Consult your healthcare provider if you experience any adverse effects or if your symptoms persist or worsen.

From the Research

Metamucil and Miralax Usage

  • Metamucil is a fiber supplement that contains psyllium, a soluble fiber that can help promote regular bowel movements and prevent constipation 2.
  • Miralax is a brand name for polyethylene glycol (PEG), an osmotic laxative that can help increase the amount of water in the stool and make it easier to pass 3.

Efficacy of Metamucil and Miralax

  • Studies have shown that psyllium, the active ingredient in Metamucil, can be effective in improving stool frequency and consistency, and reducing symptoms of constipation 2.
  • PEG, the active ingredient in Miralax, has been shown to be effective in treating functional constipation and fecal impaction, and is considered a first-line treatment for these conditions 3, 4.

Combination Therapy

  • There is limited research on the specific combination of Metamucil in the morning and Miralax at night, but studies suggest that combining fiber supplements with osmotic laxatives like PEG can be an effective treatment strategy for chronic constipation 5, 4.

Safety and Side Effects

  • Both Metamucil and Miralax are generally considered safe and well-tolerated, but can cause side effects such as bloating, gas, and abdominal pain 2, 3, 4.
  • It is recommended to start with a low dose and gradually increase as needed, and to drink plenty of water when taking these medications to minimize side effects.

References

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.