Best Fibre Supplement in the UK (2026): Ranked by Cost Per Gram of Fibre
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: Konsyl Daily Psyllium Fiber Powder. Pick methylcellulose instead only if psyllium makes you gassy, or inulin only to feed gut bacteria.
Informational summary, not medical advice.
Ranked by fibre type, evidence, and cost per gram of fibre, never commissions.
The picks
Konsyl Daily Psyllium Fiber Powder
Plain psyllium husk, a single ingredient with no flavouring or sweeteners. It has the lowest cost per gram of fibre in this list, and its label is listed in the NSF/ANSI 173 registry in our check. Start here.
Check price on Amazon →Metamucil 4-in-1 Psyllium Powder, Sugar-Free Orange
Psyllium husk with flavour and a sweetener added, in sugar-free orange. It gives less fibre per serving than our top pick and costs more per gram of fibre. Fine if taste is what gets you to take it.
Check price on Amazon →Benefiber Prebiotic Fiber Powder, Unflavored (wheat dextrin)
Wheat dextrin is not psyllium. It dissolves in drinks and is sold as a prebiotic, so it does not bulk the way psyllium does. Its label is listed in the NSF/ANSI 173 registry in our check. It costs more per gram of fibre than our top pick.
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: wheat dextrin is a different type from psyllium and does not bulk the same way, see fibre types compared.
| Product | Type | Fibre/serving | |
|---|---|---|---|
| Konsyl: Daily Psyllium Fiber Powder | Psyllium | 5 g | Price → |
| Benefiber: Prebiotic Fiber Powder, Unflavored (wheat dextrin) | Wheat dextrin | 3 g | Price → |
| Metamucil: 4-in-1 Psyllium Powder, Sugar-Free Orange | Psyllium | 3 g | Price → |
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 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 the labels we reviewed, and each brand site was read for a lot certificate on 19 September 2026. 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.
Buying fiber on Amazon.co.uk: the products on this page
These are the 3 products on this page that Amazon.co.uk lists, each with a button to its own page there. We do not show a price here. Check the price on Amazon.co.uk before you buy.
| Product | Buy |
|---|---|
| Benefiber Prebiotic Fiber Powder, Unflavored | Check price → |
| Konsyl Daily Psyllium Fiber Powder | Check price → |
| Metamucil 4-in-1 Psyllium Powder, Sugar-Free Orange | Check price → |
Three checks on the Amazon.co.uk 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. 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. A listing that says “240 count” at two pieces a serving is 120 days, so compare the cost per serving, not the cost per piece.
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 Konsyl Daily Psyllium Fiber Powder. Choose methylcellulose 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 has the lowest cost per gram of fibre in our list. Inulin powder can also be cheap, but it 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