After reviewing supplements costing $49 a month that contain a few hundred milligrams of fiber, this is worth stating plainly: a bottle of plain konjac fiber costs around $17, contains 60 servings, and delivers roughly ten times the fiber per serving. It also carries a genuine safety warning that most listicles omit. Both facts belong in the same review.
Product Overview
NOW Foods Glucomannan is a single-ingredient fiber supplement derived from konjac root (Amorphophallus konjac). There is no proprietary blend, no probiotic, and no metabolic marketing story — it is glucomannan in a vegetarian capsule.
The serving size is three capsules at 575 mg each, giving about 1,725 mg per serving, with 60 servings in a 180-capsule bottle. NOW Foods is a long-established supplement manufacturer selling through its own site and most major retailers.
Why we rate this well despite it being the least exciting product here: it publishes its serving size and servings per container clearly, the dose is in the range research actually uses, and it does not pretend to be something it is not. In a category full of $50 capsules containing sub-research doses, that combination is rare.
Label, Ingredients, and Amounts
| Active ingredient | Amount per serving |
|---|---|
| Glucomannan (Amorphophallus konjac) | 575 mg per capsule — approximately 1,725 mg per 3-capsule serving |
| Total carbohydrate | 2 g per serving (5 calories) |
| Manufacturer | NOW Foods |
|---|---|
| Serving size | 3 veg capsules — approximately 1,725 mg glucomannan |
| Servings per container | 60 servings (180 veg capsules) |
| Other ingredients | Vegetarian capsule. Full excipient list is on the physical label |
| Intended use | Marketed to support regularity and healthy weight management as a soluble dietary fiber |
| Directions | Follow the label. Glucomannan must be taken with a full glass of water — see the warnings below |
| Warnings | Glucomannan expands with water and carries a documented choking and oesophageal obstruction risk if taken with insufficient liquid or by anyone with a swallowing difficulty. Take with a full glass of water and do not take immediately before lying down |
| Allergens | Not stated in the materials we reviewed — check the physical label |
| Pricing | Around $16.52–$21.59 for 180 capsules depending on retailer — roughly 28–36 cents per serving |
| Subscription options | Varies by retailer; NOW Foods products are widely available through subscription programmes at major retailers |
| Refund policy | Varies by retailer |
| Shipping | Varies by retailer. No cold-chain requirement — this is a shelf-stable fiber, unlike the live-probiotic products in this category |
How the Manufacturer Says It Works
Glucomannan is a soluble dietary fiber with an unusually high water-holding capacity. When it absorbs water it forms a viscous gel, which physically slows gastric emptying and adds bulk to stomach contents. NOW Foods markets it for regularity and healthy weight management — both structure-function claims within what a supplement may say.
The relevance to the GLP-1 conversation is indirect but real: soluble fiber that reaches the colon is fermented into short-chain fatty acids, and slowed gastric emptying is one of the same physical effects GLP-1 medications produce — albeit by a completely different route and to a far smaller degree.
Available Scientific Support
Glucomannan is among the more-studied fiber supplements. Randomized trials have examined its effect on satiety, body weight, and cholesterol, generally using doses of 2 to 4 grams per day taken before meals with water. At about 1,725 mg per serving, this product reaches that range at two to three servings daily.
The most consistent findings are for regularity and for modest effects on post-meal satiety. Some trials have reported small reductions in body weight; others have found no significant effect. Cholesterol findings have been somewhat more consistent than weight findings.
The broader evidence for soluble fiber and satiety is covered in our fiber and appetite guide.
Limitations of the Evidence
- Weight-loss evidence is mixed. Systematic reviews have generally concluded that the evidence does not support recommending glucomannan as a weight-loss treatment, even though individual trials show modest effects.
- Effect sizes are small. Where weight effects appear, they are measured in a small number of kilograms over months — a different order of magnitude from prescription GLP-1 outcomes.
- Trials vary in dose and timing. Taking fiber before meals with water is not the same protocol as taking it at an arbitrary time, and results depend on adherence to that detail.
- Tolerability limits real-world use. Bloating and gas are common when starting, and some people simply stop.
- It is not a metabolic treatment. Fiber supports regularity and satiety; it does not address insulin resistance the way a medication might.
Pros and Cons
Pros
- Serving size and servings per container published clearly
- Dose is in the range published research actually uses — unlike most of this category
- Roughly 28–36 cents per serving
- Single ingredient, no proprietary blend
- Shelf-stable — no cold-chain or refrigeration concerns
- Long-established manufacturer with wide retail availability
- Marketing is restrained and does not invoke GLP-1 medications
- Vegetarian capsule
Cons
- Documented choking and obstruction risk if taken incorrectly
- Requires three capsules per serving, and multiple servings daily to reach trial doses
- Systematic reviews do not support it as a weight-loss treatment
- Bloating and gas are common when starting
- No third-party certification published
- Allergen statement not published in the materials we reviewed
- Can interfere with absorption of oral medications if timing is not managed
Who It May Be Best For
This suits someone who wants to try soluble fiber for satiety or regularity at a dose that actually resembles the research, without paying for branding. If you have read about fiber and appetite and want to test it cheaply, this is the honest way to do that.
It may also suit someone on a GLP-1 medication dealing with constipation — a very common and under-discussed side effect. Discuss timing with your prescriber, since fiber can affect absorption of oral medications and GLP-1s already slow gastric emptying. See our GI side effects guide.
Who Should Avoid It
Do not take glucomannan if you have any difficulty swallowing. Because it expands with water, it can obstruct the oesophagus. This is a documented risk, not a theoretical one, and it has prompted regulatory warnings in several countries.
- Anyone with a swallowing difficulty, oesophageal narrowing, or a history of obstruction.
- Anyone unable to take it with a full glass of water, or who would take it immediately before lying down.
- Anyone with an existing bowel obstruction or significant gastrointestinal disease, without medical advice.
- Anyone taking oral medications with a narrow therapeutic window, without advice on timing — fiber can reduce absorption.
- Anyone expecting meaningful weight loss. The evidence does not support that expectation.
Alternatives
- Prefer a different fiber: psyllium has comparable evidence for regularity and a long safety record — the same water precautions apply.
- Want gut-microbiome support instead: see the probiotic options.
- Want metabolic marker support: Thorne Berberine-500, subject to interaction checks.
- Better satiety lever than any supplement: see our protein guide.
Frequently Asked Questions
How much glucomannan is in a serving?
The serving size is 3 capsules at 575 mg each, so about 1,725 mg per serving. A 180-capsule bottle provides 60 servings. That is closer to the doses used in published research than any other product we reviewed in this category.
What is the choking risk with glucomannan?
Glucomannan absorbs water and expands substantially. Taken with too little liquid, or by someone with a swallowing difficulty or a narrowed oesophagus, it can swell before reaching the stomach and cause choking or obstruction. This is a documented risk that has prompted regulatory warnings in several countries. Always take it with a full glass of water, never immediately before lying down, and not at all if you have any swallowing problem without medical advice.
Does glucomannan help with appetite?
It has a plausible mechanism — it forms a viscous gel that slows gastric emptying and adds bulk, which can increase fullness. Trial results are mixed: some studies show modest satiety and weight effects, others show none, and systematic reviews have generally concluded the evidence is not strong enough to recommend it as a weight-loss treatment.
Can I take it with a GLP-1 medication?
Ask your prescriber first. GLP-1 medications already slow gastric emptying, so adding a bulking fiber can compound gastrointestinal side effects. Fiber can also interfere with the absorption of oral medications, so timing matters. Many people on GLP-1s do use fiber for constipation, but it should be a deliberate decision.
Is it worth taking over just eating more fiber?
Whole food fiber comes with nutrients a capsule does not, and it is cheaper still. A supplement is useful mainly when hitting a fiber target through food is genuinely difficult. Neither approach is a weight-loss treatment.
Supplement Disclaimer & Review Date
These statements have not been evaluated by the Food and Drug Administration. Dietary supplements are not intended to diagnose, treat, cure, or prevent any disease. Dietary supplements are not FDA-approved medications, are not reviewed by the FDA for safety or effectiveness before they go on sale, and are not a substitute for prescription treatment.
Nothing on this page is medical advice, and nothing here should be read as a promise of weight loss or of any particular result. Supplements can interact with prescription medications and are not appropriate for everyone. Talk to a doctor or pharmacist who knows your medical history before starting any supplement — particularly if you are pregnant or breastfeeding, take prescription medication, manage a chronic condition, or are already taking a GLP-1 medication.
Details about NOW Foods Glucomannan 575 mg come from the manufacturer's own published materials as of the date below. Ingredients, amounts, pricing, and policies change frequently — check the current label and product page before purchasing.
Last reviewed: August 5, 2026
Check the Current Label
Ingredients, amounts, pricing, and policies change. Verify against the current product page before buying.