Best Fiber Supplements 2026: Cost per Effective Dose
10 g of fiber costs $0.38 to $4.69 at list price across every size of the 34 fiber supplements we price. Plain psyllium powder is among the cheapest, and it is the fiber with the best evidence for constipation. 10 of the 34 are on a public testing list.
By Erin Rose Updated October 12, 2026 How we score
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.
What fiber costs, best value first
| Product and size | Per 10 g | A serving |
|---|---|---|
| Micro Ingredients Organic Inulin FOS Powder 2.2 lb tub, list $33.28, 2.3 g of fiber in 1 scoop (2.6 g)No testing list found | $0.38 | $0.09 |
| Viva Naturals Organic Psyllium Husk Powder 24 oz tub, list $24.99, 4 g of fiber in 1 teaspoon (5 g)No testing list found | $0.46 | $0.18 |
| Nutricost Prebiotic Fiber Powder, Unflavored 1 lb tub, list $19.95, 7 g of fiber in 1 scoop (8 g)No testing list found | $0.50 | $0.35 |
| NOW Organic Inulin Prebiotic Powder 8 oz tub, list $16.99, 4 g of fiber in 1 level teaspoon (about 4 g)No testing list found | $0.75 | $0.30 |
| Konsyl Daily Psyllium Fiber Powder 60-serving bottle, list $25.99, 5 g of fiber in 1 teaspoon (6 g)NSF/ANSI 173 | $0.87 | $0.43 |
| Metamucil 4-in-1 Psyllium Powder, Sugar-Free Orange 113-serving bottle, list $29.99, 3 g of fiber in 1 rounded teaspoon (5.8 g)No testing list found | $0.88 | $0.27 |
| Benefiber Prebiotic Fiber Powder, Unflavored 8.7 oz tub, list $19.99, 3 g of fiber in 2 teaspoons (4 g)NSF/ANSI 173 | $1.07 | $0.32 |
Also sold: Citrucel Methylcellulose Fiber Powder (methylcellulose). Its label gives no serving weight, so we cannot price it per gram of fiber.
10 of the 34 are on a public testing list (NSF, USP or Informed, searched September 22, 2026 to October 6, 2026). To choose by need, see the best fiber, scored; every psyllium priced is on the psyllium cost page.
Why per 10 g of fiber?
A serving can be a teaspoon, a tablespoon, 5 capsules or 3 gummies, and each holds a different amount of fiber. Per 10 g of fiber compares them fairly. 10 g a day is about the dose in constipation trials. A serving of capsules holds about 1 to 2 g of fiber and of gummies 5 to 8 g, so 10 g takes many of them.
Amazon sets its own prices. If its price is lower than the list price here, your cost is lower too.
Sources
- Prices: each brand’s own list price, its regular one-time price, for every size it sells (Walgreens, iHerb, Vitacost or Sam’s Club where the brand sells nothing itself), checked October 6, 2026. We quote no Amazon prices; Amazon is only where the buy links go.
- Testing lists: NSF/ANSI 173, NSF Certified for Sport and Informed Choice read October 6, 2026; USP Verified and Informed Sport as listed on September 22, 2026.