Best Fiber Supplement for Weight Loss and GLP-1 Users (2026)
Buy Konsyl Daily Psyllium: plain psyllium husk, $0.58 per 10 g of fiber, on a public testing list. Psyllium is the fiber with the best evidence for constipation, a known side effect of Ozempic, Wegovy and Zepbound. Fiber’s effect on weight is small and uncertain.
Our pick for GLP-1 and weight loss
Buy Konsyl Daily Psyllium
5 g of fiber in a teaspoon, from psyllium husk and nothing else. NSF/ANSI 173 is a public list of supplements tested against their labels, and this tub is on it. Start with 1 teaspoon a day.
Buy on Amazon · $25.99- Want Metamucil? Metamucil Original, with sugar is psyllium too. It costs $0.85 per 10 g of fiber, 1.5 times our pick, and we did not find it on a testing list.
Which fiber supplements are worth buying on a GLP-1 drug? (5)
Three of the five fibers below are on a public testing list. Tap a badge to open the listing. Cost is per 10 g of label fiber at Amazon’s price on November 6, 2026.
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Our pick
Konsyl Daily Psyllium
Plain psyllium husk. 90 teaspoons in the 19 oz tub we link.
$0.58 per 10 g of fiber
Buy on Amazon · $25.99 -
Wheat dextrin, not psyllium
Benefiber Prebiotic Fiber
3 g of fiber in 2 teaspoons. It adds fiber you cannot taste, but a 2017 review found wheat dextrin does not act as a laxative (McRorie 2017).
$0.72 per 10 g of fiber
Buy on Amazon · $13.48 -
Guar fiber, not psyllium
Sunfiber (Tomorrow’s Nutrition)
6 g of fiber a scoop. The label says it dissolves clear. In one trial in people with IBS, 6 g a day of this kind of guar fiber eased bloating (Niv 2016).
$1.39 per 10 g of fiber
Buy on Amazon · $24.99
Not on a testing list (2)
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Psyllium husk flakes
Yerba Prima Psyllium Husk
Not on a testing list
4.5 g of fiber in a rounded tablespoon of whole husk flakes, plain psyllium with no sweetener.
$0.65 per 10 g of fiber
Check price -
Psyllium with 4 g of sugar a serving
Metamucil Original, with sugar
Not on a testing list
3 g of fiber in a rounded teaspoon, plus 4 g of sugar. The label allows up to 3 a day.
$0.85 per 10 g of fiber
Check price
Costs are Amazon prices on November 6, 2026, divided by the servings in the pack we link, then scaled to 10 g of fiber. A badge counts only when the listing names the same product we price. Not on a list means we found no listing, not that it failed a test. More on each program: third-party tested fiber.
How should you take fiber on a GLP-1 drug?
Start with 1 teaspoon of Konsyl Daily Psyllium a day, stirred into a full glass of water and drunk right away. Over a few weeks, work up to 3 teaspoons (15 g), the most the label allows. The label on psyllium and other gel-forming fibers says to take it with at least 8 ounces of fluid, because with too little it can swell and block the throat (21 CFR 201.319).
Go slowly. Doses above 10 g a day worked for constipation, and stool counts rose most after 4 weeks or more (BDA 2025), but fiber causes gas and bloating, most of all when the dose rises too fast (Wang 2026). Nausea and bloating are already common on these drugs (Wegovy label; Zepbound label), so add one teaspoon at a time.
Take other medicines 2 hours before or after fiber (Metamucil label). Both drug labels say the drug slows stomach emptying and can change how oral medicines are absorbed, so the gap matters here. In the weight trials pooled by Gibb 2023, psyllium was taken just before meals, so a teaspoon before your biggest meal matches the research.
What fiber has been tested for
- Constipation Helps above 10 g a day Psyllium helped adults with chronic constipation, on low-certainty evidence, in trials that were not about GLP-1 drugs.
- Weight loss A little, not reliably Reviews disagree, from a small gain to a loss. No review studied people on these drugs.
- Feeling full Mixed Some trials found less hunger. Others did not, and the effect is small.
- Gas and bloating More gas Fiber caused more gas than placebo. Inulin added gas, but not bloating, in two trials.
- On a GLP-1 drug Not tested No published trial of a fiber supplement in people taking one (PubMed search, Nov 6, 2026).
Does fiber help with constipation from Ozempic, Wegovy or Zepbound?
Probably, but no trial has tested it in people on these drugs. A PubMed search on November 6, 2026 found no randomized trial of a fiber supplement in people taking semaglutide, tirzepatide or liraglutide, and a 2026 review calls for them (Wang 2026). Constipation is listed on all three labels, and the Wegovy and Zepbound trials show how common it is.
| Drug and dose | On the drug | On placebo | Adults, drug and placebo |
|---|---|---|---|
| Ozempic 0.5 mg, weekly (type 2 diabetes) | 5% | 1.5% | 260 and 262 |
| Ozempic 1 mg, weekly (type 2 diabetes) | 3.1% | 1.5% | 261 and 262 |
| Wegovy 2.4 mg, weekly | 24% | 11% | 2,116 and 1,261 |
| Zepbound 5 mg, weekly | 17% | 5% | 630 and 958 |
| Zepbound 10 mg, weekly | 14% | 5% | 948 and 958 |
| Zepbound 15 mg, weekly | 11% | 5% | 941 and 958 |
In adults with chronic constipation in general, psyllium worked. Across 16 trials, 66% responded to fiber and 41% to control, but only at more than 10 g a day (van der Schoot 2022). The 2023 US gut doctors’ guideline found psyllium the only fiber supplement that appeared effective, at about 2.3 more spontaneous bowel movements a week than placebo, though the evidence is low certainty (AGA-ACG 2023). That guideline’s advice to use fiber was conditional, while its advice to use PEG, a laxative powder, was strong; it says a trial of fiber is reasonable for mild constipation, before PEG or alongside it. The UK dietitians’ guideline gives psyllium its strongest recommendation, also on low-quality evidence (BDA 2025).
Will a fiber supplement help you lose weight?
Possibly a little. Reviews of fiber trials range from a 3.6 kg gain to a 2.5 kg loss, and the review of 62 trials found 0.33 kg. These reviews are not about people on a GLP-1 drug, and a 2026 review says weight loss from fiber alone is typically more modest than with these drugs (Wang 2026).
| Review | Trials and what was taken | Weight change |
|---|---|---|
| Jovanovski 2020 | 62 trials, 3,877 adults. Viscous fiber added to a normal diet, 4 weeks or longer. | Down 0.33 kg (0.14 to 0.51 kg). More in people with overweight. |
| Thompson 2017 | 12 trials, 609 adults with overweight or obesity. Soluble fiber supplements, 2 to 17 weeks, no calorie limit. | Down 2.52 kg (0.79 to 4.25 kg). Results differed a lot between trials. |
| Darooghegi Mofrad 2020 | 22 trials of psyllium in adults. Psyllium alone. | Down 0.28 kg, and the range includes no change. Not a clear effect. |
| Gibb 2023 | 6 trials, 354 adults with overweight or obesity. Psyllium, 10.8 g a day on average, just before meals, 4.8 months on average. | Down 2.1 kg (1.6 to 2.6 kg). The authors work for Procter & Gamble, which makes Metamucil. |
| Gholami 2025 | 27 trials of psyllium in adults. Psyllium alone. | Up 3.57 kg (1.43 to 5.72 kg): a gain, not a loss. Its BMI and waist results were not significant either way. |
So buy fiber for constipation and a steadier gut, and treat any weight change as a small extra. If you are trying to lose weight on one of these drugs, the bigger lever is protein and strength training: see the best protein powder on a GLP-1 drug.
Does fiber make you feel full?
It can, but the evidence is mixed and the effect is small. A 2024 review found trials that showed less hunger, less eating and more fullness after fiber, and others that did not, and it says more studies are needed (Akhlaghi 2024). Stretching the stomach and slowing how fast it empties are among the ways fiber may work. Your GLP-1 drug already slows stomach emptying (Wegovy and Zepbound labels), and protein is the priority at meals, so if a glass of fiber leaves you too full to eat it, take less.
Which fiber causes the least gas and bloating?
Fiber as a group caused more gas than placebo (van der Schoot 2022), and the UK guideline singles out inulin: it added gas, but not bloating, in two constipation trials at 12 and 15 g a day (BDA 2025). Fibers that gut bacteria ferment make gas (ACG 2021), and psyllium is a gel-forming fiber that resists fermentation (McRorie 2017). If psyllium bloats you even when you go slowly, Sunfiber (Tomorrow’s Nutrition) is a different type, guar fiber. In one trial in people with IBS, 6 g a day of partially hydrolyzed guar gum, the kind of guar fiber Sunfiber is, eased bloating over 12 weeks (Niv 2016).
Who should check with a prescriber before adding fiber?
Check first if you have trouble swallowing (21 CFR 201.319), constipation with stomach pain, nausea or vomiting (Metamucil label), or slow stomach emptying (gastroparesis). The Wegovy and Zepbound labels do not recommend those drugs in severe gastroparesis. A 2026 expert-panel summary for family doctors, funded by an educational grant from Bayer, says psyllium may worsen delayed stomach emptying, and that GI specialists prefer PEG 3350, a laxative powder, over psyllium in gastroparesis (AAFP 2026). The same panel’s first choice for constipation on these drugs was PEG 3350, which your pharmacist can explain. See a doctor if constipation lasts more than 7 days on fiber or you see rectal bleeding (Metamucil label).
Do glucomannan or konjac fiber pills work for weight loss?
No. In 8 trials in adults with overweight, glucomannan lost no more weight than placebo: 0.22 kg, a gap that could be chance (Onakpoya 2014). NIH’s fact sheet on weight-loss supplements lists little to no effect on body weight and choking concerns for tablet forms (NIH Office of Dietary Supplements).
More on fiber: the best fiber supplement for anyone, how much fiber a day, fiber types compared and what else to take on a GLP-1 drug.
Questions
Can I take fiber with Wegovy tablets?
Wait at least 30 minutes after the tablet before you eat, drink or take any other pill by mouth, which includes a glass of fiber (Wegovy label). After that, keep fiber 2 hours away from your other medicines (Metamucil label).
Is food or a supplement better for fiber?
Food comes first: beans, whole grains, fruit with the skin on, vegetables and nuts (NIDDK). Most US adults fall short, at 16.6 g a day on average against targets of 21 to 38 g (USDA; IOM 2002). A teaspoon of Konsyl Daily Psyllium adds 5 g.
Sources
- Novo Nordisk. WEGOVY (semaglutide) prescribing information, adverse reactions table for adults with obesity or overweight, and warnings on gastroparesis and gastric emptying. DailyMed. Read November 6, 2026.
- Novo Nordisk. OZEMPIC (semaglutide) prescribing information, adverse reactions table for adults with type 2 diabetes. DailyMed. Read November 6, 2026.
- Eli Lilly. ZEPBOUND (tirzepatide) prescribing information, adverse reactions table, warnings on gastroparesis and drug interactions. DailyMed. Read November 6, 2026.
- A Focus on Managing Constipation Associated With GLP-1 RA Therapy. AAFP CME Bulletin, August 2026; grant-funded by Bayer through Medscape; an expert-panel summary. AAFP
- van der Schoot A, et al. The Effect of Fiber Supplementation on Chronic Constipation in Adults: An Updated Systematic Review and Meta-Analysis of Randomized Controlled Trials. Am J Clin Nutr. 2022. PubMed
- Chang L, et al. American Gastroenterological Association-American College of Gastroenterology Clinical Practice Guideline: Pharmacological Management of Chronic Idiopathic Constipation. Gastroenterology. 2023. PubMed
- Dimidi E, et al. British Dietetic Association Guidelines for the Dietary Management of Chronic Constipation in Adults. J Hum Nutr Diet. 2025. PubMed
- Jovanovski E, et al. Can dietary viscous fiber affect body weight independently of an energy-restrictive diet? A systematic review and meta-analysis of randomized controlled trials. Am J Clin Nutr. 2020. PubMed
- Thompson SV, et al. Effects of isolated soluble fiber supplementation on body weight, glycemia, and insulinemia in adults with overweight and obesity: a systematic review and meta-analysis of randomized controlled trials. Am J Clin Nutr. 2017. PubMed
- Darooghegi Mofrad M, et al. The effects of psyllium supplementation on body weight, body mass index and waist circumference in adults: A systematic review and dose-response meta-analysis of randomized controlled trials. Crit Rev Food Sci Nutr. 2020. PubMed
- Gibb RD, et al. Psyllium is a natural nonfermented gel-forming fiber that is effective for weight loss: A comprehensive review and meta-analysis. J Am Assoc Nurse Pract. 2023. PubMed Two authors are listed at Procter & Gamble, which makes Metamucil.
- Gholami Z, et al. The effect of psyllium consumption on anthropometric indices: a systematic review and dose-response meta-analysis of randomized controlled trials. J Health Popul Nutr. 2025. PubMed
- Wang Y, et al. Dietary Fiber and Glucagon-Like Peptide-1 Receptor Agonists in Obesity Management: Converging Mechanisms, Interactions, and Strategies for Durable Weight Control. Adv Nutr. 2026. PubMed
- Akhlaghi M, et al. The role of dietary fibers in regulating appetite, an overview of mechanisms and weight consequences. Crit Rev Food Sci Nutr. 2024. PubMed
- Lacy BE, et al. ACG Clinical Guideline: Management of Irritable Bowel Syndrome. Am J Gastroenterol. 2021. PubMed
- McRorie JW Jr, et al. Understanding the Physics of Functional Fibers in the Gastrointestinal Tract: An Evidence-Based Approach to Resolving Enduring Misconceptions about Insoluble and Soluble Fiber. J Acad Nutr Diet. 2017. PubMed
- Niv E, et al. Randomized clinical study: Partially hydrolyzed guar gum (PHGG) versus placebo in the treatment of patients with irritable bowel syndrome. Nutr Metab (Lond). 2016. PubMed
- Onakpoya I, et al. The efficacy of glucomannan supplementation in overweight and obesity: a systematic review and meta-analysis of randomized clinical trials. J Am Coll Nutr. 2014. PubMed
- NIH Office of Dietary Supplements. Weight Loss and Dietary Supplements: Fact Sheet for Health Professionals. ods.od.nih.gov
- Metamucil Therapy for Regularity Drug Facts label, Procter & Gamble. DailyMed. FDA, 21 CFR 201.319, labeling of water-soluble gums. eCFR.
- Testing lists: NSF/ANSI 173 (info.nsf.org) and Informed Choice, searched by brand and product name on the dates shown on our testing page. Each badge above links to its program.
- Fiber intake: USDA What We Eat in America, NHANES 2017 to March 2020; Institute of Medicine, Dietary Reference Intakes, 2002; NIDDK, Eating, Diet and Nutrition for Constipation.