Best Fibre Supplement in the UK (2026): Ranked by Cost Per Gram of Fibre
Informational summary, not medical advice. Prices are Amazon prices, verified September 20, 2026; they change.
Prices and cost per day here are from our US catalogue in USD. UK prices differ, use them to compare products with each other, not to budget in pounds. Buy buttons open the product on Amazon.co.uk; where a brand is not sold in the UK, the button opens an Amazon.co.uk search instead of a dead page.
The best fibre supplement is not a brand but a type bought cheaply: psyllium husk.Psyllium is the best-studied type, and bought as plain husk powder it's also among the lowest cost per gram of fibre. Top pick: NOW Psyllium Husk Powder, Organic (12 oz). Pick methylcellulose (Citrucel) instead only if psyllium makes you gassy, or inulin only to feed gut bacteria.
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| Item | Value |
|---|---|
| NOW Foods | $0.043 |
| NOW Foods | $0.043 |
| Konsyl | $0.058 |
| Benefiber | $0.073 |
| Metamucil | $0.074 |
| Citrucel | $0.310 |
The picks
NOW Psyllium Husk Powder, Organic (12 oz)
Plain organic psyllium husk: 7 g fibre (6 g soluble) per serving, at a low cost per gram in this list. Start here.
Check price on Amazon →Konsyl Daily Psyllium Fiber Powder (19 oz)
A single ingredient, psyllium husk, with no flavoring or sweeteners, at 90 servings. Nearly as cheap per gram as the top pick; the choice if you want psyllium and nothing else.
Check price on Amazon →Citrucel Methylcellulose Fiber Powder
Methylcellulose bulks and gels like psyllium but is not fermented at all, so it produces the least gas. It costs more per gram here and is not a prebiotic.
Check price on Amazon →The full ranking
Every product here, ranked by cost per gram of fibre. Remember the type column matters as much as the price: inulin is cheap but it's a prebiotic, not a bulking fibre, and wheat dextrin is a different type again, see fibre types compared.
| Product | Type | Fibre/serving | Price | Cost/g fibre | |
|---|---|---|---|---|---|
| NOW Foods: NOW Psyllium Husk Powder, Organic (12 oz) | Psyllium | 7 g | $11.30 | $0.043 | Price → |
| NOW Foods: NOW Organic Inulin Prebiotic Powder (8 oz) | Inulin (prebiotic) | 3 g | $9.90 | $0.043 | Price → |
| Konsyl: Daily Psyllium Fiber Powder (19 oz) | Psyllium | 5 g | $25.99 | $0.058 | Price → |
| Benefiber: Prebiotic Fiber Powder (wheat dextrin) | Wheat dextrin | 3 g | $13.48 | $0.073 | Price → |
| Metamucil: 4-in-1 Psyllium, Sugar-Free (72 servings) | Psyllium | 3.4 g | $17.97 | $0.074 | Price → |
| Citrucel: Methylcellulose Fiber Powder | Methylcellulose | 2 g | $18.59 | $0.310 | Price → |
NOW Psyllium Husk Powder works out to about $0.04/gram of fibre: roughly 7× cheaper per gram than methylcellulose. With psyllium, plain psyllium husk powder is the smart buy; the price difference is flavour and packaging.
How we ranked
We don't rank by tub size or brand recognition. Two things decide it:
- Fibre type & evidence first. Psyllium leads because it has the evidence (the best-studied type) and does all three fibre jobs, gels, resists fermentation, and bulks. Here's the breakdown.
- Then cost per gram of fibre. The honest value metric isn't price per tub, it's price ÷ grams of actual fibre, using each product's label serving. That's what the table above shows.
What we deliberately ignore: front-label terms like "prebiotic," "gut health," and "GLP-1 friendly" that do not describe the fibre type inside, and big milligram numbers that turn out to be small once you read the serving size.
Method: the 6 fibre products in our catalog were checked one by one against the NSF/ANSI 173 registry (3,053 listings), the USP Verified list (159 products) and the Informed Sport database (2,105 products) in our 2026-08-25 snapshots, and each brand site was read for a lot certificate on 2026-09-19. One (Konsyl) is registry-listed. The full ladder is on the third-party-tested fibre page; cost per gram uses the fibre grams on each Supplement Facts panel, not the scoop weight.
Price check · Fiber
What Fiber actually costs across the brands we track
What you pay. The 6 Fiber products here run $0.13 to $0.62 a day across 5 brands, a 4.8× gap. Some of these state a certification on the listing itself. That is a weaker claim than a certifier confirming it: a listing repeats what the brand says, and a registry entry shows what a certifier has checked.
Method: the 6 Fiber products in our catalogue, each priced at its own labelled serving rather than by pack size, across 5 brands. How we price.
Buying fiber on Amazon: the listings on this page
These are the 6 Amazon listings behind this page, identified by ASIN so you land on the same container we priced. Each cost is the Amazon price we saw on 2026-10-09, divided by the label serving count. Prices change; check the price on Amazon before you buy. Cheapest per day: NOW Organic Inulin Prebiotic Powder at $0.13. Cheapest one we found in a public certification registry: Konsyl Daily Psyllium Fiber Powder at $0.29.
| Listing | ASIN | Price | Cost per day | Buy |
|---|---|---|---|---|
| NOW Organic Inulin Prebiotic Powder | B000MGSI1K | $9.90 | $0.13 | Check price → |
| Benefiber Prebiotic Fiber Powder | B01978FIZC | $13.48 | $0.22 | Check price → |
| Metamucil 4-in-1 Psyllium, Sugar-Free | B000052Y5Q | $17.97 | $0.25 | Check price → |
| Konsyl Daily Psyllium Fiber Powder | B0D1DB2D6V | $25.99 | $0.29 | Check price → |
| NOW Psyllium Husk Powder, Organic | B002N0OFEM | $11.30 | $0.30 | Check price → |
| Citrucel Methylcellulose Fiber Powder | B001F0R76O | $18.59 | $0.62 | Check price → |
Three checks on the Amazon listing itself
- Who is selling it. The “Sold by” line should read the brand, Amazon, or the brand’s named distributor.
- The lot and the expiry on arrival. For a product with a certificate lookup or a registry listing, the lot number on the container is what you check, not the listing. A lot older than the certificate date, or an expiry inside a year, is a reason to return it.
- The serving count, not the piece count. The per-day figures above use the label’s serving; a listing that says “240 count” at two pieces a serving is 120 days, so compare cost per serving rather than cost per piece.
Product links go to Amazon and we may earn a commission if you buy. It never changes which product we pick or what we say about it. How we choose.
Cost per gram of fibre, product by product
Each line is the arithmetic behind the ranking: the container price divided by the fibre grams it holds (label fibre per serving times servings), then what it takes to reach 7 g of fibre a day. Cheapest first.
- NOW Psyllium Husk Powder, Organic (12 oz) (Psyllium): 7 g of fibre per 1 tbsp (9 g), 38 servings at $11.30, so $0.043 per gram; 7 g a day takes 1 serving and costs about $0.30, or $110 a year.
- NOW Organic Inulin Prebiotic Powder (8 oz) (Inulin (prebiotic)): 3 g of fibre per 1 tsp (~3 g), 75 servings at $9.90, so $0.043 per gram; 7 g a day takes 3 servings and costs about $0.30, or $111 a year.
- Konsyl Daily Psyllium Fiber Powder (19 oz) (Psyllium): 5 g of fibre per 1 tsp (6 g), 90 servings at $25.99, so $0.058 per gram; 7 g a day takes 2 servings and costs about $0.41, or $148 a year.
- Benefiber Prebiotic Fiber Powder (wheat dextrin) (Wheat dextrin): 3 g of fibre per 2 tsp (~3.5 g), 62 servings at $13.48, so $0.073 per gram; 7 g a day takes 3 servings and costs about $0.51, or $187 a year.
- Metamucil 4-in-1 Psyllium, Sugar-Free (72 servings) (Psyllium): 3.4 g of fibre per 1 rounded tsp (~5.8 g), 72 servings at $17.97, so $0.074 per gram; 7 g a day takes 3 servings and costs about $0.51, or $188 a year.
- Citrucel Methylcellulose Fiber Powder (Methylcellulose): 2 g of fibre per 1 tbsp (2 g fiber), 30 servings at $18.59, so $0.310 per gram; 7 g a day takes 4 servings and costs about $2.17, or $792 a year.
The spread is the whole story of this category: the most expensive gram of fibre here costs 7.2 times the cheapest, and a higher price per gram does not by itself mean a better fiber. What the premium buys is a flavour system, a brand, or a different fibre type with a specific use (methylcellulose if psyllium is gassy; inulin only to feed gut bacteria). If the goal is 7 g of fiber a day, the plain husk at the top of the list is the answer, and the Metamucil vs NOW comparison shows the premium in one pair.
Frequently asked questions
What is the best fibre supplement?
For most people, plain psyllium husk powder, the most-studied fibre and among the lowest cost per gram. Our pick is NOW Psyllium Husk Powder. Choose methylcellulose (Citrucel) if psyllium is gassy, or inulin only to feed gut bacteria.
Is Metamucil or generic psyllium better?
Same active ingredient, psyllium. Metamucil adds flavour/sweetener, costs more per gram of fibre, and delivers a bit less psyllium per serving. Fine for taste; plain psyllium husk powder wins on value.
What is the best fibre for the money?
Plain psyllium husk powder, ~4–6 cents per gram of fibre, several times cheaper than methylcellulose or branded blends. Inulin powder is similarly cheap but is a prebiotic, not a bulking fibre.
Related
- Fibre Types Compared: which type of fiber does what
- Fibre Dosage Guide: how much per day and how to ramp up
- Best Psyllium Supplement: a deeper psyllium-only ranking, including capsules and Metamucil
- All Fibre Guides
Sources
- van der Schoot A, et al. "The Effect of Fiber Supplementation on Chronic Constipation in Adults." Am J Clin Nutr. 2022. PMID: 35816465
- Nagarajan N, et al. "Fiber supplementation in irritable bowel syndrome." Eur J Gastroenterol Hepatol. 2015. PMID: 26148247
- McRorie JW Jr, McKeown NM. "Understanding the Physics of Functional Fibers in the Gastrointestinal Tract." J Acad Nutr Diet. 2017. PMID: 27863994