Best Fiber Supplements 2026: Cost per Effective Dose
Top pick for Fiber: NOW Psyllium Husk Powder, Organic (12 oz) — 7g per 1 tbsp (9 g), Non-GMO Project Verified, USDA Organic, $0.37/day. Our pick.
Registry check · Fiber
Does anyone independently verify Fiber supplements?
1 of the 6 Fiber products on this page is confirmed in NSF/ANSI 173: Konsyl Daily Psyllium Fiber Powder (19 oz). Konsyl Daily Psyllium Fiber Powder (19 oz) does not show the mark on the listing, so the table’s certification column, which repeats the listing, does not show it either. For the others, the listing may name a certification, but we did not find it in a public registry — that is not evidence against them, only an absence of independent confirmation.
Certification is not a dosing guarantee. Across the whole catalogue, certified products reach the clinically studied dose 57% of the time and uncertified ones 71% — a gap too small to mean anything (Fisher p = 0.185). Read the Fiber dose column either way.
The 6 products on this page checked against all 5,317 US NSF, USP and Informed Sport listings, 2026-08-25. Full method and limitations.
What Fiber labels show
Priced per day, these fiber products run $0.13 to $0.62 — a 4.8× gap between the cheapest and dearest fiber here, across 5 brands.
Which row that favours is not obvious: NOW Foods NOW Organic Inulin Prebiotic Powder (8 oz) is cheapest per serving at $0.13, but its serving sits below the median here, so part of that price gap is simply a smaller capsule.
All Fiber Supplements Compared
The fibre type matters more than the brand. Fermentable fibres such as inulin have the stronger prebiotic evidence and reliably feed bifidobacteria, but they also produce the gas and bloating people blame on the product; wheat dextrin and methylcellulose ferment far less and are much better tolerated at the cost of a weaker prebiotic effect. Whichever you choose, build up over a week or two — starting at a full serving is the usual reason a fibre supplement gets abandoned. This page compares fibre types against each other; if you have already settled on psyllium and just want the cheapest way to take it, the psyllium husk comparison covers whole husk, powder and capsules side by side.
| Product | Brand | Dose / Serving | Cost / Day | Certification (as labelled) | Pick | Buy |
|---|---|---|---|---|---|---|
| NOW Organic Inulin Prebiotic Powder (8 oz) | NOW Foods | 3g / 1 tsp (~3 g) | $0.13 | USDA Organic, Non-GMO | Buy | |
| Benefiber Prebiotic Fiber Powder (wheat dextrin) | Benefiber | 3g / 2 tsp (~3.5 g) | $0.22 | None listed | Buy | |
| Metamucil 4-in-1 Psyllium, Sugar-Free (72 servings) | Metamucil | 3.4g / 1 rounded tsp (~5.8 g) | $0.25 | None listed | Buy | |
| Konsyl Daily Psyllium Fiber Powder (19 oz) | Konsyl | 5g / 1 tsp (6 g) | $0.29 | Single-ingredient psyllium | Quality Pick | Buy |
| NOW Psyllium Husk Powder, Organic (12 oz) | NOW Foods | 7g / 1 tbsp (9 g) | $0.37 | Non-GMO Project Verified, USDA Organic | Our Pick | Buy |
| Citrucel Methylcellulose Fiber Powder | Citrucel | 2g / 1 tbsp (2 g fiber) | $0.62 | FDA OTC monograph drug | Buy |
Our Picks
Our Pick: NOW Psyllium Husk Powder, Organic (12 oz)
7g per 1 tbsp (9 g). Non-GMO Project Verified, USDA Organic. $0.37/day. 38 servings per container at $14.10.
Quality Pick: Konsyl Daily Psyllium Fiber Powder (19 oz)
5g per 1 tsp (6 g). Single-ingredient psyllium. $0.29/day. 90 servings per container at $25.99.
The shelf · Fiber
The Fiber shelf is unusually consistent
Across 6 products from 5 brands, the cheapest day is NOW Organic Inulin Prebiotic Powder (8 oz) at $0.13 and the priciest is Citrucel Methylcellulose Fiber Powder at $0.62, a gap of 4.8×. With prices this close, which of these Fiber products has been independently checked matters more than the price.
Method: the 6 Fiber products above, compared on label facts, serving size, servings per container, form, price. Not a dosing recommendation.
How these 6 Fiber products were ranked
1 of these 6 is confirmed in a certifier's registry — the only fiber row where the claim is independently backed — and the rest are ranked on cost per day at the labelled serving. Commission does not enter it: the rate is the same whichever fiber you buy. Full methodology.