Reviewed on 9/3/2021

What Is Psyllium and How Does It Work?

Psyllium is an over-the-counter (OTC) laxative used to treat constipation.

  • Psyllium is available under the following different brand names: Fiberall, Metamucil, and Perdiem Fiber.

What Are Dosages of Psyllium?

Dosages of Psyllium:
  • See manufacturer's recommendations on the packaging.


  • Adult: 2.5-7.5 g in 8 oz of water orally, up to 30 g/d divided orally or
  • 1 teaspoonful or 1 tablespoon in 8 oz of water orally one to three times daily, depending on the product
  • Children under 6 years old: Safety and efficacy not established
  • Children 6-12 years old: 1.25-15 g/day orally in 8 oz of water in divided doses
  • Children over 12 years old: 2.5-7.5 g in 8 oz of water orally, up to 30 g/day in divided doses

Other Indications and Uses


Super Tips to Boost Digestive Health: Bloating, Constipation, and More See Slideshow

What Are Side Effects Associated with Using Psyllium?

Side effects of psyllium include:

  • Abdominal or stomach cramping
  • Constipation
  • Gas (flatulence)
  • Impaction

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

What Other Drugs Interact with Psyllium?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Psyllium has no known severe, serious, or moderate interactions with other drugs.
  • Mild interactions of psyllium include:
    • sodium picosulfate

This information does not contain all possible interactions or adverse effects. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns, or for more information about this medicine.

What Are Warnings and Precautions for Psyllium?


  • This medication contains psyllium. Do not take Fiberall, Metamucil, or Perdiem Fiber if you are allergic to psyllium or any ingredients contained in this drug.

Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately.


Effects of Drug Abuse

Short-Term Effects

  • See "What Are Side Effects Associated with Using Psyllium?"

Long-Term Effects

  • See "What Are Side Effects Associated with Using Psyllium?"


Pregnancy and Lactation

  • Psyllium may be acceptable for use during pregnancy
  • Either animal studies show no risk but human studies are not available or animal studies showed minor risks and human studies were done and showed no risk
  • There is no data available on psyllium use while breastfeeding
  • Psyllium is not absorbed systemically, therefore it is unlikely to pose a risk in breastfeeding


Pancreatitis is inflammation of an organ in the abdomen called the pancreas. See Answer
Medscape. Psyllium.

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