Which Fiber Supplements Are Third-Party Tested?

Our recommendation

Buy Konsyl Daily Psyllium Fiber Powder

Plain psyllium husk, the fiber with the best evidence for constipation. NSF/ANSI 173 checks that the tub holds what the label says. 5 g of fiber a teaspoon.

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• Drug-tested in sport? Momentous Fiber+ Unflavored is on NSF Certified for Sport + NSF/ANSI 173, which also screens for drugs banned in sport.
• Only take gummies? vitafusion FiberWell Sugar Free Fiber Gummies is on USP Verified. It adds fiber, but it is not a constipation fix (BDA 2025).
• Other fiber gives you gas? Tomorrow's Nutrition Sunfiber, guar fiber on Informed Choice. In one trial in people with IBS, 6 g a day eased bloating more than a placebo, though overall symptoms did not improve (Niv 2016). If you have IBS, ask your doctor which fiber to try.

Safety: Take psyllium with a full glass of water. Do not take it if you have trouble swallowing. Take other medicines 2 hours before or after. All the cautions.

✓ On a testing list (10 we score)

An outside program checked each of these and lists it by name. NSF/ANSI 173 and USP Verified check that the tub holds what the label says; Informed Choice and NSF Certified for Sport screen for drugs banned in sport. The other 4 are in the full list at the bottom. More on each list

1. 

   Our pick

   Konsyl Daily Psyllium Fiber Powder

   ✓ NSF/ANSI 173

   5 g of fiber in 1 teaspoon (6 g) · psyllium husk

   $0.87 per 10 g of fiber

   Buy on Amazon
2. 

   If other fiber gives you gas

   Tomorrow's Nutrition Sunfiber

   ✓ Informed Choice

   6 g of fiber in 1 scoop (7 g) · PHGG (guar fiber)

   $1.39 per 10 g of fiber

   Buy on Amazon
3. 

   Also screened for drugs banned in sport

   Momentous Fiber+ Unflavored

   ✓ NSF Certified for Sport✓ NSF/ANSI 173

   6 g of fiber in 2 scoops (6 g fiber) · psyllium, resistant potato starch, rice bran

   $2.22 per 10 g of fiber

   Buy on Amazon
4. 

   If you will only take a gummy

   vitafusion FiberWell Sugar Free Fiber Gummies

   ✓ USP Verified

   5 g of fiber in 2 gummies · fiber blend

   $0.60 per 10 g of fiber

   Buy on Amazon
5. 

   Benefiber Prebiotic Fiber Powder, Unflavored

   ✓ NSF/ANSI 173

   3 g of fiber in 2 teaspoons (4 g) · wheat dextrin

   $1.07 per 10 g of fiber

   Buy on Amazon
6. 

   Garden of Life Dr. Formulated Organic Fiber, Unflavored

   ✓ NSF/ANSI 173

   5 g of fiber in 1 tablespoon (6 g) · acacia blend

   $1.01 per 10 g of fiber

   Buy on Amazon

Not on any testing list (24 we score)

We searched all five lists and did not find these. Metamucil, Citrucel, NOW, Viva Naturals, Organic India, Kirkland and Nutricost have no fiber product on any list. Here are the two best known.

1. 

   Lowest-cost psyllium scoring 7 or more

   NOW Whole Psyllium Husks

   Not on a public list

   7 g of fiber in 2 level tablespoons (10 g) · psyllium husk

   $0.51 per 10 g of fiber

   Check price
2. 

   Metamucil 4-in-1 Psyllium Powder, Sugar-Free Orange

   Not on a public list

   3 g of fiber in 1 rounded teaspoon (5.8 g) · psyllium husk

   $0.88 per 10 g of fiber

   Check price

Costs are per 10 g of fiber at each brand’s list price (or the named store where the brand sells none itself), the same figures as our best fiber guide.

What “third-party tested” means

A company outside the brand checks the product and lists it by name, so you can look it up yourself. There are two kinds. A contents program checks that the product holds what the label says. A banned-substance program screens for drugs banned in sport, which matters only if you are drug-tested. “Third-party tested” printed on a label, with no program named, is the brand’s word.

What the testing lists show

NSF/ANSI 173: Konsyl psyllium

NSF Certified for Sport: Momentous Fiber+

The big brands on no list

Metamucil, Citrucel, NOW, Viva Naturals, Organic India, Kirkland and Nutricost have no fiber product on any of the five lists. We searched each list in full, by company and by product name. That includes the 4 Metamucil products we score. Citrucel is sold as an over-the-counter drug, not a supplement.

Benefiber is the big brand that is listed: NSF/ANSI 173 lists 11 Benefiber products under its maker, Haleon.

Benefiber on NSF/ANSI 173

NSF/ANSI 173: Haleon (Benefiber)

What the brand says, and what we could confirm

A claim with no listing is the brand’s word. Physician’s Choice says “Third-party tested for safety, quality and effectiveness”. Micro Ingredients says “third-party tested, of course.” NOW says its organic psyllium is “packaged and quality tested in the USA”. None of the three names a lab, and none is on a list. Thorne says its FiberMend “has been third-party tested and certified to verify what’s in the package matches what’s on the label”, and NSF/ANSI 173 does list it, so you can check that one.

How to check your tub

1. Find the mark. Look for an NSF, USP or Informed mark. “Third-party tested” with no mark is a claim.
2. Open the program’s own list. NSF/ANSI 173, USP Verified, NSF Certified for Sport, Informed Choice, Informed Sport. Or search all five on our testing-list index.
3. Search the product, not just the brand. A brand with one listed product can sell others that are not.
4. Try the maker’s name. NSF/ANSI 173 files products under the company that makes them: Benefiber under Haleon, Konsyl under Konsyl Pharmaceuticals.

Questions

Sources

1. NSF/ANSI 173 (info.nsf.org), NSF Certified for Sport (nsfsport.com) and Informed Choice (choice.wetestyoutrust.com), read October 6, 2026. USP Verified and Informed Sport as listed on September 22, 2026.
2. Brand claims: each brand’s label (NIH Dietary Supplement Label Database), drug label (DailyMed) or store page, read October 6, 2026. Prices: each brand’s list price, checked October 6, 2026. We quote no Amazon prices.
3. McRorie JW Jr, McKeown NM. Understanding the Physics of Functional Fibers in the Gastrointestinal Tract. J Acad Nutr Diet. 2017. PubMed 27863994 (McRorie is listed at Procter & Gamble, which makes Metamucil, on a 2015 paper (Gibb 2015, PubMed 26561625).)
4. Niv E, et al. Nutr Metab (Lond). 2016. PubMed 26855665. Dimidi E, et al. (BDA 2025). J Hum Nutr Diet. 2025. PubMed 41081513
5. FDA. 21 CFR 201.319 (eCFR) and the Metamucil drug facts label (DailyMed), read October 6, 2026.