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Metamucil Fiber Review: Is It Safe and Effective?

By Brandi Givens, RDN

Medically Reviewed by Anthony Dugarte, MD

Published on April 23, 2021

Dietitian Rating:


About This Rating
The average rating of this product is calculated based on the evaluation of the following factors:
  • Support for Claims:5.0
  • Ingredient Safety:3.0
  • Value for the Price:4.0
  • Brand Transparency:4.0

Metamucil is a fiber supplement that may support digestive health and reduce LDL cholesterol. I would consider recommending Metamucil products for those struggling to get enough fiber from a balanced diet.

Written by
Brandi Givens, RDN
Registered Dietitian Nutritionist
Brandi Givens has been a registered dietitian nutritionist (RDN) since 2010, and an internationally board-certified lactation consultant (IBCLC) since 2016.
Medically Reviewed by
Anthony Dugarte, MD
Medical Reviewer
Anthony Dugarte, M.D., C.S.C.S. is a health and wellness writer and medical content reviewer. In addition to dedicating the last 7 years to medical research, Dr. Dugarte also has more than a decade of experience in strength and conditioning, nutrition, and rehabilitative exercise, as well as authoring and reviewing health and wellness-related content.

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Metamucil Fiber Review: Is It Safe and Effective?


  • Offers an alternative way to get one form of fiber when people are struggling to get enough fiber from food.
  • Health claims are mostly evidenced based.
  • Has additional health benefits beyond digestion.


  • Consumers may mistake fiber supplements as being just as healthful as fiber-rich food.
  • To reach some of the health claims, consumers must take a lot of product per day.
  • Potential for extra gas and bloating in people who are not used to fiber in their diet.

What Is Metamucil Psyllium Fiber?

Metamucil is a soluble (70%) and insoluble (30%) fiber supplement made from the psyllium husk of the dried Plantago ovata seed.

Psyllium is generally regarded as safe by the FDA and is used in commercial cereals and as a food thickener in products like ice cream.

Sold in the United States since 1934 as a medicine to help with constipation and mild diarrhea, in recent decades, Metamucil has claimed to support heart health by lowering cholesterol, support healthy blood sugar levels, and support appetite control.

Metamucil comes in several different forms, including sweetened powders that are mixed into water and a capsule form; these are the main focus of this article.

Metamucil also has a newer gummy product marketed as a prebiotic supplement made with different ingredients, chicory root and corn fiber, instead of psyllium.

Metamucil Is Not a Weight Loss Supplement

People have recently become interested in using Metamucil for weight loss.

This may be because of Metamucil’s claim to support appetite control and because of some of the confusing wording on the website, such as “Feel what lighter feels like” and “Metamucil works by helping you feel lighter and more energetic.”

While there have been studies that show that psyllium powder mixed with water and taken before meals can suppress appetite, this should not be confused with weight loss. (1)

There is no solid evidence that people have lost weight by using Metamucil, according to this review of 22 studies. (2)

Evaluation of Ingredients and Benefits

The active ingredient of 4-in-1 Metamucil powders and 3-in-1 capsules is psyllium husks or mucilage.

Metamucil makes the following claims for the powder (the capsule form excludes the appetite control claim):

Claim 1: Supports Digestive Health

Psyllium has been used for centuries to fight constipation as a bulk-forming laxative.

The soluble fiber becomes a viscous, gel-like material when it comes in contact with water in the gut, softening stool and helping to carry everything along through the intestines.

While it may seem counterintuitive, Metamucil can also help ease the symptoms of mild diarrhea by absorbing excess water from the loose stool, solidifying diarrhea, and easing symptoms.

This study showed an increase in microbiome health with the use of psyllium supplementation, especially when the subjects were constipated prior to treatment. (3)

Claim 2: Supports Heart Health by Lowering Cholesterol

In 1998, the Food and Drug Administration reviewed the evidence and (FDA) approved the health claim that psyllium fiber can lower cholesterol in adequate amounts. (4)

For example, this meta-analysis concluded that 10.2 g of soluble psyllium fiber was successful in reducing low-density lipoprotein (LDL). (5)

This study involving 50 children showed a reduction in LDL with the intervention of 6.4 g of soluble fiber. (6)

Because of these dose-specific findings, the FDA requires psyllium supplement dosage must add up to at least 7 g of soluble fiber to meet the health claim.

To reach the 7 g of fiber from this product, a consumer must take 1 rounded teaspoon of the powder 3 times daily with 8 oz of water, or swallow 5 capsules 4 times a day (20 capsules) with lots of water.

Claim 3: Supports Healthy Blood Sugar Levels

In 2014 a petition was filed with the FDA requesting authorization of the health claim that psyllium husk reduces the risk of type 2 diabetes.

The FDA reviewed studies to date, and its current statement is, “Psyllium husk may reduce the risk of type 2 diabetes, although the FDA has concluded that there is very little scientific evidence for this claim.” (7)

However, in 2018 the American Diabetes Foundation reviewed all relevant studies up to date and found that psyllium fiber is a useful tool in glycemic control. (8)

Claim 4: Supports Appetite Control

Metamucil powder has been shown to help control appetite between meals in some studies. But, a review of 22 studies found that it did not help induce weight loss. (2)

Support for Claimed Benefits

Below is our summary of the available evidence for the claimed benefits of Metamucil Fiber based on the available research:

Supports digestive health5/5
Supports heart health by lowering cholesterol5/5
Supports healthy blood sugar levels5/5
Supports appetite control5/5

Side Effects, Safety, and Dosage

The possible side effects of Metamucil are stomach pain, bloating, and intestinal gas. Although rare, allergic reaction has been reported.

The website warns that taking their product may interfere with medication absorption and should be taken at least two hours before medications.

It’s important to take Metamucil with lots of water to avoid the risk of choking and prevent bowel obstruction. Capsules should be swallowed while in an upright position. (9)

More than occasional constipation may be a sign of a more serious condition and should be discussed with your doctor.

Always speak with your doctor before taking any supplement.

The dosage of Metamucil depends on the goal of using the product. The website recommends:

  • For digestive health: 2–5 capsules up to 4 times daily (8–20 capsules) daily or 1 rounded teaspoon of powder mixed with 8oz water up to 3 times daily.
  • For heart health by lowering cholesterol: 5 capsules up to 4 times daily (up to 20 capsules) or 1 rounded teaspoon of powder mixed with 8oz water up to 3 times daily.
  • For blood sugar support: 5 capsules 4 times daily (20 capsules) or 1 rounded teaspoon of powder mixed with 8oz water up to 3 times daily.
  • For appetite control: No recommendation for capsules. 2 rounded teaspoons of powder mixed with 8oz water up to 3 times daily.


In my opinion, the cost of Metamucil capsule supplements is very expensive.

The Amazon price is 15 cents per capsule. At 20 capsules daily, this is $3.00/day or $90 for 30 days.

The cost of Metamucil 4-in-1 sugar-free powder on Amazon is $25.44 for a 180-serving canister, which works out to 14 cents per serving.

At the recommended 3 servings daily, this comes out to 42 cents per day and would cost $12.72 for a 30-day supply.

buy Metamucil on Amazon

How Metamucil Compares to Alternatives

Compared to other fiber supplements, psyllium fiber in Metamucil has been the most successful in providing evidence for multiple health benefits. (10)

I found several generic alternatives on Amazon at a lower cost, with psyllium as the only ingredient. The price for these alternatives was as low as $7.95 for a 30-day supply.

As a dietitian, I always encourage food over supplements.

Consider that a serving of cooked black beans can cost as little as 11 cents per serving and has twice as much soluble fiber. That works out to about $3.30 for a 30-day supply.

Prunes may be just as effective as psyllium in fighting constipation. (11)

Also, consider that oatmeal has similar results in fighting cholesterol. Food is always a better option than a supplement when it comes to fiber. (10)

The Bottom Line

Metamucil fiber supplements can be a useful tool for digestion and heart health in people struggling with getting enough fiber from food.

There is strong evidence to support the claims made by Metamucil.

I would recommend it for some people, with the understanding that some may experience digestive discomfort when starting this supplement.

A Word from Our RD

There are times when fiber can be difficult to get from diet alone, and a supplement may be warranted.

This is especially true when a person is ill, has multiple food aversions, intolerances, or allergies.

However, getting fiber from food is superior to supplementation because we benefit from whole food.

While psyllium is a plant-based supplement, it is just a functional fraction of the seed, stripped from the rest of its nutrients.

Getting adequate fiber is just another reason why plant-based dietary eating patterns like the Mediterranean and DASH diets are great lifelong plans.

Plant-based eating has the evidence to back the same health claims as Metamucil and offers much more.

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At WellnessVerge, we only use primary references for our articles, including peer reviewed medical journals or well-respected academic institutions.

  1. Satiety effects of psyllium in healthy volunteers:
  2. The effects of psyllium supplementation on body weight, body mass index and waist circumference in adults: A systematic review and dose-response meta-analysis of randomized controlled trials:
  3. The Effect of Psyllium Husk on Intestinal Microbiota in Constipated Patients and Healthy Controls:
  4. CFR - Code of Federal Regulations Title 21:
  5. Cholesterol-lowering effects of psyllium intake adjunctive to diet therapy in men and women with hypercholesterolemia: meta-analysis of 8 controlled trials:
  6. Soluble fiber enhances the hypocholesterolemic effect of the step I diet in childhood:
  7. Psyllium husk intake and risk of type 2 diabetes: an evidence-based scientific and regulatory review of a qualified health claim conducted by the US Food and Drug Administration.:
  8. Should Viscous Fiber Supplements Be Considered in Diabetes Control? Results From a Systematic Review and Meta-analysis of Randomized Controlled Trials:
  9. Intestinal obstruction caused by a laxative drug (Psyllium): A case report and review of the literature:
  10. Fiber supplements and clinically proven health benefits: How to recognize and recommend an effective fiber therapy:
  11. Fiber supplements and clinically proven health benefits: How to recognize and recommend an effective fiber therapy: