Best Fiber Supplements in the US (April 2026): An Evidence-Based Comparison

How we evaluated these products

We reviewed fiber supplements available on Amazon.com based on four criteria:

Evidence. Does peer-reviewed research support the fiber type for the claimed benefit? We prioritised fibers backed by systematic reviews and meta-analyses, not single small studies.

Dosing transparency. Does the product clearly state the fiber content per serving, and does that serving align with the doses used in clinical research?

Ingredient purity. We favored products with minimal additives. A fiber supplement should contain fiber, not sweeteners, fillers, or proprietary blends that obscure the actual dose.

Value. We calculated cost per effective daily dose, not cost per gram. A cheap powder that requires 20g to hit the research threshold is not cheaper than a premium product that works at 12g.

We include affiliate links to Amazon.com. These earn us a small commission at no extra cost to you. Our editorial choices are independent of these links. Full disclosure at /disclosure.

What is the American fiber gap?

The numbers are stark. The USDA Dietary Guidelines for Americans recommend 25g of fiber per day for women and 34g for men.¹ Average American intake sits at approximately 15g per day. That is a deficit of 10-19g every single day.

For Americans taking GLP-1 medications like semaglutide (Ozempic, Wegovy) or tirzepatide (Mounjaro, Zepbound), the gap widens further. Reduced appetite and lower food volume mean even less dietary fiber, while the medications themselves slow gastric emptying and contribute to constipation in 5-24% of users. For a deeper look at how GLP-1 medications create constipation problems, see our detailed guide.

What are the main fiber types in US supplements?

Before the product list, a quick orientation. Most fiber supplements sold in the US fall into one of five categories.

Psyllium husk is a gel-forming soluble fiber that absorbs water and adds bulk to stool. It is the most widely recommended fiber supplement type by US healthcare professionals and the active ingredient in Metamucil. Strong evidence for both regularity and LDL cholesterol reduction (Wei et al., 2009).²

Chicory inulin is a soluble prebiotic fiber fermented by gut bacteria to produce short-chain fatty acids. It is the only fiber with a proprietary EFSA Article 13.5 health claim: chicory inulin from BENEO’s Orafti source “contributes to maintenance of normal defecation by increasing stool frequency” at 12g/day (EFSA, 2015).³ High-FODMAP. Start slowly.

Resistant starch is a type of starch that resists digestion in the small intestine and reaches the colon intact. Research suggests it may support GLP-1 secretion naturally, though the evidence is still emerging. Some supplement brands market this connection aggressively.

PHGG (partially hydrolysed guar gum) is a low-viscosity soluble fiber that dissolves completely, is tasteless, and produces minimal gas. Clinical evidence supports its use for IBS-related symptoms (Giannini et al., 2006).⁴ The gentlest option for GLP-1 users.

Blends combine two or more fiber types, typically inulin + psyllium + acacia. These can offer broader support but make it harder to identify which fiber causes any side effects.

For a detailed comparison of the two most common types, see our chicory inulin vs. psyllium husk guide.

What are the 7 best fiber supplements available in the US?

1. Metamucil 4-in-1 Psyllium Fiber (Unflavored, No Sweetener)

Fiber type: Psyllium husk Fiber per serving: 2.4g soluble fiber per teaspoon (3g total fiber) Price: ~$24 for 114 servings Cost per day at 2 servings: ~$0.42

The household name. Metamucil is the most widely sold fiber supplement in the US and the brand most gastroenterologists reference. The unflavored, no-added-sweetener version is the cleanest option in the Metamucil range: just psyllium husk powder with no artificial colors or flavors.

At 2.4g of soluble fiber per teaspoon, you need 2-3 servings per day to approach a clinically relevant dose. This is consistent with the doses used in psyllium research (7-10g/day). Always take with at least 250ml of water per serving.

The trade-off: per serving, Metamucil is more expensive than bulk psyllium from other brands. You pay for the brand trust and pharmacy-aisle familiarity.

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2. Konsyl Daily Psyllium Fiber (Unflavored)

Fiber type: Psyllium husk Fiber per serving: 5g fiber per 6g serving Price: ~$20 for 90 servings (19 oz) Cost per day at 1-2 servings: ~$0.22-0.44

The purist’s choice. Konsyl contains a single ingredient: 100% psyllium husk powder. No sugar, no sweeteners, no fillers. Founded in 1934, Konsyl is the oldest psyllium brand in the US and was originally a prescription product.

Higher fiber density per serving than Metamucil (5g vs. 2.4g soluble fiber) means fewer daily servings to reach a meaningful dose. The unflavored version mixes into water, smoothies, or food without altering taste.

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3. NOW Foods Psyllium Husk Caps (500mg, 500 Count)

Fiber type: Psyllium husk Fiber per serving: 1.1g fiber per 3-capsule serving Price: ~$19 for 500 capsules Cost per day at 9 capsules (3 servings): ~$0.34

The capsule option for people who dislike the texture of psyllium powder in water. NOW Foods is a well-established US supplement brand with GMP certification and third-party testing. Non-GMO Project Verified.

The trade-off is dose efficiency: even at the maximum suggested dose of 9 capsules per day (3 servings), you only get about 3.3g of fiber. That is significantly less than a single scoop of powder. Capsules work best as a complement to dietary fiber, not a sole source. If you want more fiber per serving from NOW Foods, their psyllium husk powder (B002RWUNYM) delivers ~6g per tablespoon.

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4. Supergut GLP-1 Daily Support

Fiber type: 4-in-1 prebiotic fiber blend (resistant potato starch, green banana fiber, oat beta-glucan, soluble vegetable fiber) Fiber per serving: 6g fiber per serving Price: ~$30-32 for 20 servings Cost per day: ~$1.50-1.60

Supergut markets directly to GLP-1 users with claims about supporting natural GLP-1 production. The core ingredients include Solnul (resistant potato starch) and green banana fiber, which early research suggests may stimulate GLP-1 secretion via short-chain fatty acid production in the colon. Available in unflavored, Raspberry Lemon, Blood Orange, and Watermelon Lime. Also stocked at Target, Walmart, GNC, and Walgreens.

The science is real but early. A 2023 study in Nature Medicine found that resistant starch supplementation altered gut microbiota composition and increased SCFA production.⁵ However, the direct link between supplemental resistant starch and clinically meaningful GLP-1 increases in humans is not yet established with the same rigor as, say, the EFSA claim for chicory inulin.

At ~$1.50 per serving, this is among the most expensive options on our list. The premium reflects the GLP-1 marketing positioning more than the evidence base currently supports.

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5. HUM Flatter Me Fiber

Fiber type: Prebiotic fiber + 18 digestive enzymes Fiber per serving: 10g prebiotic fiber per serving Price: ~$30 for 10 servings Cost per day: ~$3.00

HUM Nutrition positions Flatter Me Fiber as a GLP-1 booster product. According to HUM Nutrition, their product contains 10g of prebiotic fiber alongside 18 full-spectrum digestive enzymes. The brand claims the product “doubles GLP-1 levels within 30 minutes of a meal.” Available in Strawberry Lemon, Pineapple Passion Fruit, and Unflavored.

At $3.00 per serving, this is the most expensive option on our list by a wide margin. The 10g fiber dose is meaningful, but the GLP-1 doubling claim is a manufacturer’s claim that should be evaluated carefully. The digestive enzymes may help with bloating but are a separate mechanism from fiber supplementation.

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6. SoWell Fiber (Apple Cinnamon, 14 Stick Packs)

Fiber type: Triple fiber blend (psyllium husk + guar gum + apple pectin) Fiber per serving: 5g fiber per stick pack Price: ~$35 for 14 stick packs ($31.49 with Subscribe & Save) Cost per day: ~$2.50

SoWell is a physician-founded brand that positions itself specifically for GLP-1 medication users. The product combines psyllium husk, guar gum, and apple pectin with 100mg magnesium glycinate and 7.5 billion CFU Bacillus subtilis probiotic. Also available at Sprouts, Walmart, and Walgreens. SoWell also sells electrolytes and protein products for the GLP-1 market.

The physician-founded angle and added magnesium and probiotic give SoWell a more complete formulation for GLP-1 users, who often experience both constipation and electrolyte issues. But at $2.50 per stick pack for 5g of fiber, you are paying a steep convenience premium. A scoop of Konsyl provides the same amount of psyllium at a fraction of the cost.

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7. Micro Ingredients Organic Triple Fiber (2 lb)

Fiber type: Chicory inulin + psyllium husk + acacia fiber blend Fiber per serving: 6g fiber per 8g serving Price: ~$37 for 2 lbs (~113 servings) Cost per day at 2 servings (12g): ~$0.65

The best-value blend on Amazon.com. Micro Ingredients combines three complementary fibers: chicory inulin for prebiotic support, psyllium for bulk-forming action, and acacia for gentle, slowly fermented soluble fiber. USDA Organic certified, non-GMO, and unflavored.

At 7g per serving, two scoops per day provide 14g of mixed fiber across three mechanisms. The trade-off with any blend: if you experience side effects, you cannot isolate which fiber is the cause. Best for people who already know they tolerate both inulin and psyllium individually.

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How do these products compare?

How to choose the right fiber supplement

If you want the simplest, most studied option: Start with psyllium husk. Konsyl or Metamucil. Take with plenty of water. This is the fiber type with the largest clinical evidence base for regularity.

If you are on a GLP-1 medication: Start with a single-ingredient fiber and ramp slowly. Psyllium is the safest first choice. If nausea is a concern, look for a PHGG product (OptiFibre or Healthy Origins, available from Amazon). Avoid jumping straight to high-dose inulin, which can worsen gas and bloating when gastric emptying is already slowed.

If you are on a budget: Konsyl Daily Psyllium Fiber or bulk psyllium husk powder offers the lowest cost per effective dose. Micro Ingredients Triple Fiber is the best value if you want a blend.

If you want prebiotic support specifically: Chicory inulin at 12g/day has the strongest prebiotic evidence and the only proprietary EU health claim. Micro Ingredients Triple Fiber includes inulin but at a lower dose per scoop than a single-ingredient inulin powder.

If you want a GLP-1-specific product: Supergut and SoWell are formulated for this audience. The science behind resistant starch and GLP-1 is promising but not yet at the same evidence level as psyllium for constipation or inulin for prebiotic function. You are paying a premium for the targeted formulation.

Which fiber should you choose?

If your main concern is constipation relief, start with psyllium husk powder. It has the most clinical evidence for improving stool frequency and consistency. Take with at least 250ml of water per serving. Browse psyllium husk powder on Amazon

If you are starting a GLP-1 medication (Ozempic, Wegovy, Mounjaro, Zepbound), consider PHGG (partially hydrolyzed guar gum) or Sunfiber first. PHGG is the gentlest fiber for GLP-1 users because it produces minimal gas, dissolves completely, and is low-FODMAP certified. Avoid jumping straight to high-dose inulin in the first weeks. Browse PHGG / Sunfiber on Amazon

If you want prebiotic and microbiome support, look for chicory inulin powder. At 12g/day it carries the only proprietary EU health claim for bowel function. Start at 4g/day and ramp up over 2 weeks to avoid gas and bloating. Browse chicory inulin powder on Amazon

If you have IBS or FODMAP sensitivity, start with PHGG or acacia fiber. Both are slow-fermenting, low-FODMAP, and produce significantly less gas than inulin or psyllium. Browse acacia fiber on Amazon

If you already know your tolerance and want broader microbiome coverage, look for a fiber blend that combines two or more soluble fibers. Trade-off: if side effects occur, you cannot isolate which fiber is responsible. Browse prebiotic fiber blends on Amazon

Frequently asked questions

What is the best fiber supplement for GLP-1 users in the US?

There is no single best option. PHGG (partially hydrolysed guar gum) is the gentlest for GLP-1 users with nausea. Psyllium husk has the broadest evidence base for constipation. Chicory inulin offers the strongest prebiotic support. Start with one type, ramp slowly, and time your dose at least 1 hour before or 2 hours after your GLP-1 injection.

Is psyllium or inulin better for constipation?

Different mechanisms. Psyllium absorbs water and adds bulk to stool (mechanical action). Inulin feeds beneficial gut bacteria that produce short-chain fatty acids (prebiotic action). Both support regularity, but psyllium has more clinical evidence specifically for constipation. Inulin has the EFSA health claim for stool frequency at 12g/day. We compared them in detail: chicory inulin vs. psyllium husk.

How much fiber should you take per day?

The USDA recommends 25g per day for women and 34g per day for men from all sources. Most Americans consume about 15g from food. A supplement providing 10-15g per day can close most of the gap. Start low and increase gradually over 2-3 weeks.

Can you take fiber supplements with Ozempic or Wegovy?

Yes, but timing matters. Take fiber supplements at least 1 hour before or 2 hours after your injection. For oral semaglutide (Rybelsus), the 30-minute empty-stomach fasting period means fiber must be taken at a separate meal entirely. Read more: Oral Wegovy and fiber: how the fasting rule changes everything.

What is the cheapest effective fiber supplement?

Bulk psyllium husk powder offers the lowest cost per effective dose. Konsyl Daily Psyllium Fiber costs roughly $0.22 per serving at the recommended dose. NOW Foods Psyllium Husk Caps are the cheapest capsule option at roughly $0.08 per capsule, though you need 10 capsules per day.

Looking for fiber supplements in another market? See our guides for the UK, Canada, Australia, Netherlands, or Nordics.

* Affiliate link. See our disclosure for details.

This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting, stopping, or changing any medication or supplement regimen.

Last reviewed: April 7, 2026. Prices and availability are approximate and may change.