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Constipation means having fewer than three bowel movements per week. You may have straining during your bowel movements and a difficult time passing hard, dry stools. When you struggle with constipation, you may turn to an over-the-counter supplement, such as Benefiber or Metamucil. These supplements are brand-name versions of different types of fiber used to improve overall bowel health.

Benefiber and Metamucil work in the same way. They absorb water from your intestines to form softer, bulkier stools. These stools flow more easily through your digestive system, which helps you have easier bowel movements. These supplements also increase how often you have bowel movements. The charts below describe other similarities and differences of Benefiber and Metamucil.

Active ingredientBenefiberMetamucil
Wheat dextrinx
Psyllium husk powderx
Symptoms treatedBenefiberMetamucil
High cholesterolx

In addition to treating constipation, Metamucil may also help lower your cholesterol levels, and may improve your blood sugar control if you have type 2 diabetes. Benefiber, on the other hand, is not approved for these uses.

Fiber can also decrease your appetite by making you feel fuller for a longer time. However, these fiber supplements do not appear to help with weight loss directly.

You can take Benefiber or Metamucil up to three times per day, but you should increase how often you take it slowly. Start by taking it once each day. You can work up to taking the supplement three times per day over the course of one to two weeks.


Benefiber comes in as a powder. The standard adult dosage of Benefiber is two teaspoons. You can mix the powder with four to eight ounces of a beverage, such as:

  • water
  • coffee
  • juice

Stir well until the powder dissolves, which will take about one minute. Then drink the mixture.

You can also mix Benefiber with hot or cold soft foods, such as:

  • applesauce
  • pudding
  • yogurt


Metamucil comes in powder, capsule, and wafer forms.


The standard adult dosage of Metamucil powder is one rounded teaspoon mixed with at least eight ounces of a cool liquid, such as:

  • water
  • coffee
  • juice

Stir the mixture well and then drink it.


The standard adult dosage for the capsules is two to five capsules per serving. Start with two capsules per serving to see how it affects you, and then increase your dosage if needed. You can take up to four servings per day.


The typical dosage is two wafers with at least eight ounces of a hot or cold drink. You can have up to three servings per day.

In children

The dosage for Metamucil or Benefiber for children who are 12-17 years old is the same as the adult dosage.

Children who are 6-11 years old can take one teaspoon of Benefiber mixed with four to eight ounces of a beverage or soft food. For Metamucil powder, they can take ½ teaspoon mixed with eight ounces of a beverage. Ask your child’s doctor what the correct dosage is for your child if you’re using the Metamucil capsules or wafers.

For children who are 5 years or younger, ask their doctor for the recommended dosage of Benefiber and Metamucil.

Children can take either supplement up to three times per day. However, you should increase how often they take the supplement slowly: It should take one to two weeks to reach the maximum dosage per day.

Side effects

Benefiber and Metamucil can cause similar side effects, such as stomach cramping and gas. These effects may be more likely when you first start taking the supplement. Gas and stomach cramping tend to go away after a few weeks, but you can help reduce these side effects by increasing your dosage slowly over one to two weeks. Drinking plenty of fluids while taking these supplements can also help ease side effects.

In rare cases, these supplements can cause serious side effects. These can include gastrointestinal (GI) obstructions.

Learn more: Causes, symptoms, and treatments of a GI obstruction »


Benefiber and Metamucil may affect how well other medications work in your body. This is because they can decrease how well your body absorbs some medications. This means the drugs may not work as well. If you take a prescription drug by mouth, take Benefiber or Metamucil at least two hours before or two hours after taking your medication.

Benefiber and Metamucil may cause other interactions with prescription or over-the-counter drugs and other supplements. Be sure to ask your pharmacist or doctor about possible interactions before you start taking Benefiber or Metamucil.

Conditions of concern

You should not use these supplements if you have an acute stomach problem. These include:

  • appendicitis
  • ulcers
  • esophageal perforation
  • GI obstruction

Talk to your doctor if you have any stomach pain, nausea, or vomiting before you take Benefiber or Metamucil. These symptoms may mean you have an acute GI issue, and Benefiber or Metamucil could make your condition worse.

To help combat constipation, you can add Benefiber or Metamucil to your diet. These supplements can improve your bowel regularity.

Shop for Benefiber.

Shop for Metamucil.

The following tips can help you get the best results:

  • Make sure you mix Metamucil with enough water. Taking it without enough water can cause it to get very thick, which may cause choking.
  • You can reduce your chance of side effects by slowly increasing your dosage of either supplement over one to two weeks.
  • You should stop using Benefiber or Metamucil and talk to your doctor if your constipation lasts more than 7 days.
  • You should also call your doctor if you have bleeding after any bowel movement. Bleeding means you could have a bowel obstruction, perforation, or hemorrhoids.