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Dietary supplement

Prebiotic Inulin Fiber Ingredients & Drug Interactions

by NOW

Prebiotic Inulin Fiber label
See full label image
Capsule Category: Fiber And Other Nutrients
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Oct 7, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Prebiotic Inulin Fiber against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Moderate

Prebiotic Inulin Fiber is a dietary supplement by NOW with 2 active ingredients. Its ingredients are commonly taken for constipation, diarrhea, high cholesterol.Based on those ingredients, 2,025 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Dietary Fiber. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against Prebiotic Inulin Fiber by NOW

Ask about any prescription or over-the-counter medication and we check it for interactions with Prebiotic Inulin Fiber by NOW — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of Prebiotic Inulin Fiber by NOW

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Oct 8, 2026

What’s inside

Full disclosure
Ingredient Transparency · database check
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 2 of its 2 active ingredients.
  • No proprietary blends here — you can verify the dose of every single component.

The one active ingredient is fructooligosaccharides (FOS), the fiber the product is built around. That makes the active ingredient count one.

Our data also lists two inactive ingredients, polysaccharides and magnesium stearate. The facts don't describe what they do, so we won't guess at their roles.

Does it work?

Couldn't assess
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed
Not assessable

We hold no graded evidence for this product's ingredients for its stated purpose.

Why this rating?
  • The label markets this product for: prebiotic fiber to support intestinal probiotic bacteria.
  • Our graded evidence for these ingredients doesn't cover that particular purpose.

For each purpose we have on file for FOS (food allergies, atopic disease, osteoporosis, pancreatic cancer, constipation, and atopic dermatitis, also called eczema), the rating is insufficient reliable evidence to rate. In plain terms, the evidence isn't established in the data we hold, so we can't say whether FOS works for any of these uses.

The evidence, ingredient by ingredient Black Psyllium Fructo-oligosaccharides (fos)

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 2 of the 2 matched ingredients.
  • Pregnancy & breastfeeding safety ratings cover 2 of 2.
  • General safety write-ups exist for 2 of 2.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Our adverse effect data describes FOS as generally well tolerated. The most common effects are gas, bloating, abdominal pain, and belching, which are generally mild at doses under 10 grams a day.

A meta-analysis of 8 small clinical studies (2.5 to 15 grams daily for up to 8 weeks) found no increase in abdominal pain, bloating, flatulence, or intestinal sounds compared with control groups. Our safety notes advise caution, since supplement-level doses aren't well studied and the product should be used with your doctor's guidance.

Our data holds no pregnancy or breastfeeding entry for FOS, so there isn't enough information to know either way. Please talk with your doctor or pharmacist for personalized advice.

Side effects, ingredient by ingredient Black Psyllium Fructo-oligosaccharides (fos)

Meds to double-check

Moderate interaction found
Known Interaction Concern · database check
Moderate identified

The most serious documented interaction for these ingredients is Moderate. Check your medications for a personalized result.

Why this rating?
  • 1 of the 2 matched ingredients can interact with medications — Black Psyllium.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: heart-rhythm medications; lithium.
  • For scale: 2,026 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

Our data links no medication types to FOS, so no interactions are documented for the ingredient we checked. That is not a guarantee that none exist.

Your own doctor or pharmacist can compare your full medication list against this product.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with no assessable stated purpose. Moderate medication interactions have been identified, and safety information is well characterized.

This product may appeal to people looking for a fiber supplement built on FOS, though the evidence for its uses is not established in our data. If you are pregnant, breastfeeding, or prone to gas and bloating, talk with your doctor before starting.

Review it with your own doctor or pharmacist first, especially if you take ongoing medications.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 2 of 2 active ingredients matched to our full ingredient reviews (monographs). Based on the product label dated Oct 24, 2024.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about Prebiotic Inulin Fiber, straight from the product label.

Brand NOW
Barcode (UPC) 733739029690
Net contents 180 Veg Capsule(s)
Market status On market
Date entered into DSLD Oct 24, 2024
DSLD ID 313984
Product type Fiber And Other Nutrients
Supplement form Capsule
Dietary claims / uses Nutrient, All Other, Structure/Function
Intended target group(s) Vegan, Vegetarian, Adult (18 - 50 Years), Organic, Gluten Free, Dairy Free
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for Prebiotic Inulin Fiber by NOW, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
3 Veg. Capsule(s)
Maximum serving Sizes:
3 Veg. Capsule(s)
Servings per container
60
UPC/BARCODE
733739029690
IngredientAmount% DV
Calories5 Calorie(s)--
Total Carbohydrates2 Gram(s)1%
Dietary Fiber2 Gram(s)7%
Fructooligosaccharides1.95 Gram(s)--

Other ingredients: Polysaccharides, Magnesium Stearate

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
Suggested/Recommended/Usage/Directions

Suggested Usage: Take 3 capsules 2 to 3 times daily.

Formula

Inulin, a fructooligosaccharide (FOS), is a soluble prebiotic fiber that is resistant to digestion and reaches the large intestine essentially intact. Intestinal probiotic bacteria consume inulin and in turn, produce the short-chain fatty acids (SCFAs) that nourish the cells lining the colon. Inulin thus helps to maintain intestinal health and function. Inulin has a very low glycemic index and will not negatively affect serum glucose levels.

Made with organic inulin

FDA Disclaimer Statement

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.

Precautions

Caution: For adults only. Keep out of reach of children.

May cause mild transient GI discomfort.

Consult physician if pregnant/nursing, taking medication, or have a medical condition.

Not manufactured with yeast, wheat, gluten, soy, milk, egg, fish, shellfish, tree nut or sesame ingredients. Produced in a GMP facility that processes other ingredients containing these allergens.

Formulation

Natural color variation may occur in this product.

Intestinal Support Nourishes friendly bacteria

Made with organic inulin

Non GMO Project Verified nongmoproject.org

Vegetarian/Vegan

Certified Organic by QAI.

Made and quality tested in the USA with globally sourced ingredients.

Not manufactured with yeast, wheat, gluten, soy, milk, egg, fish, shellfish, tree nut or sesame ingredients.

Storage

Store in a cool, dry place after opening.

General Statements

This bottle is made from 100% PCR (post-consumer recycled) resin.

Digestive Family owned since 1968.

Seals/Symbols

GMP Quality Assured

Non GMO Project Verified nongmoproject.org

FDA Statement of Identity

A Dietary Supplement

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

Prebiotic Inulin Fiber by NOW label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

Prebiotic Inulin Fiber label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in Prebiotic Inulin Fiber by NOW

These are the 2 active ingredients this product is made of. Select any to open its full monograph.

Serving size3 Veg. Capsule(s) Dosage formCapsule Servings per container60 Amounts shown are per serving.

Most supplement products combine several ingredients, and a medication can interact with the product through any one of them. Each ingredient below shows whether it has known drug interactions.

Dietary Fiber

Interacts with
2,025 drugs
2 Gram(s) per serving

Black psyllium is a soluble-fiber supplement made from the seeds of a Plantago plant, used mostly to ease constipation and support digestive health. I...

Dietary Fiber monograph & interactions

Fructooligosaccharides

No known
interactions
1.95 Gram(s) per serving Form: Agave, Inulin

Fructo-oligosaccharides (FOS) are a type of soluble fiber that acts as a prebiotic, meaning they feed the helpful bacteria in your gut. They are gener...

Fructooligosaccharides monograph & interactions

Other (inactive) ingredients: Polysaccharides, Magnesium Stearate. These complete the product’s ingredient list but are not active constituents.

Interaction report

Prebiotic Inulin Fiber by NOW Drug Interactions

Want to check YOUR meds against Prebiotic Inulin Fiber?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

 Go to the checker
2,025Drugs
23 Moderate 2,002 Minor

Ingredients driving the most interactions

Dietary Fiber 2,025

Individual Drug Interactions

The ingredients in Prebiotic Inulin Fiber interact with 2,025 drugs. Click any drug to see the details.

1 of the 2 ingredients in Prebiotic Inulin Fiber interact with drugs. Each result below shows which ingredient is responsible. Dietary Fiber

Each ingredient & the kinds of drugs it affects

For each ingredient in Prebiotic Inulin Fiber with known interactions, here are the types of medications it can affect. Open any type for the detail — or search your exact drug in the checker above.

Dietary Fiber7 drug types · 2,025 drugs

Carbamazepine (Tegretol)

Theoretically, black psyllium might reduce the effects of carbamazepine and increase the risk for convulsions.
Theoretically, black psyllium might reduce carbamazepine absorption. A preliminary study using blond psyllium reported decreased carbamazepine bioavailability due to binding of the drug to psyllium, as well as reduction of available fluid in the gut for dissolution of the drug. This interaction may also occur with black psyllium.

Likelihood Probable Evidence D
Lithium

Theoretically, taking black psyllium at the same time as lithium might reduce lithium absorption.
The fiber in black psyllium might reduce lithium absorption and plasma levels. Some case reports describe a reduction in plasma lithium levels with concomitant administration of blond psyllium. This was reversed when psyllium was stopped. This interaction may also occur with black psyllium.

Likelihood Probable Evidence D
Metformin (Glucophage)

Theoretically, black psyllium might increase the therapeutic and adverse effects of metformin.
Animal research shows that concurrent consumption of blond psyllium with metformin slows and increases the absorption of metformin. This interaction may also occur with black psyllium. To avoid changes in absorption, take psyllium 30-60 minutes after metformin.

Likelihood Possible Evidence D
Olanzapine (Zyprexa)

Theoretically, taking black psyllium at the same time as olanzapine might reduce olanzapine absorption.
The fiber in black psyllium might decrease the absorption of olanzapine. A single case report describes a reduction in the effectiveness of olanzapine when it was concomitantly administered with an unspecified type of psyllium 3 grams orally twice daily. This effect was reversed when psyllium was stopped.

Likelihood Possible Evidence D
Digoxin (Lanoxin)

Theoretically, taking black psyllium at the same time as digoxin might reduce digoxin absorption and decrease digoxin levels.
Psyllium might bind digoxin in the gut. However, some clinical evidence suggests that psyllium does not impact digoxin absorption.

Likelihood Unlikely Evidence B
Ethinyl Estradiol

Theoretically, taking black psyllium at the same time as ethinyl estradiol might alter levels of estradiol.
Concurrent use of blond psyllium with ethinyl estradiol results in a slight increase in the extent of ethinyl estradiol absorption and a slower rate of absorption. This is unlikely to be clinically significant.

Likelihood Unlikely Evidence D
Oral Drugs

Theoretically, psyllium might increase, decrease, or have no effect on the absorption of oral drugs.
Psyllium seems to have variable effects on drug absorption. To avoid changes in absorption, take psyllium 30-60 minutes after oral medications. Animal research shows that blond psyllium delays and increases the absorption of metformin and ethinyl estradiol. Case reports and animal research suggest that blond psyllium might reduce absorption of lithium, digoxin, olanzapine, and carbamazepine. Finally, some pharmacokinetic studies show that psyllium does not affect the absorption of levothyroxine or warfarin. Although many of these studies evaluated blond psyllium, the fiber content in black psyllium may have similar effects.

Likelihood Possible Evidence B
Dietary Fiber full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Prebiotic Inulin Fiber, from the product label.

NOW

See all NOW products
Name
NOW FOODS
Street Address
395 S. Glen Ellyn Rd.
City
Bloomingdale
State
IL
ZipCode
60108
Web Address
nowfoods.com
Pharmacist Counseling Corner

Prebiotic Inulin Fiber by NOW: Common Questions

Does Prebiotic Inulin Fiber by NOW interact with any medications?
Yes. Based on its ingredients, Prebiotic Inulin Fiber has a known interaction with 2,025 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Prebiotic Inulin Fiber contains 2 active ingredients, and an interaction can come from any of them. We check every ingredient, combine the results into one list per medication, and show which ingredient and mechanism is responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
Does this product cause gas or bloating?
Gas, bloating, and abdominal pain are the most common effects listed for FOS. They are generally mild at doses under 10 grams a day, and a meta-analysis of 8 small studies found no increase in these symptoms compared with control groups.
Is this supplement effective for constipation?
Constipation is one of the uses we have on file for FOS, and its rating is insufficient reliable evidence to rate. That means the evidence isn't established in our data, so we can't say it works for this purpose.
Can I take this if I'm pregnant or breastfeeding?
Our data holds no pregnancy or breastfeeding entry for FOS, so there isn't enough information to know either way. Please talk with your doctor or pharmacist for personalized advice before taking it.
What are the inactive ingredients in this capsule?
Our data lists polysaccharides and magnesium stearate as inactive ingredients. The facts don't describe their specific roles in the product.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Not sure if Prebiotic Inulin Fiber is safe with your meds?

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Ask a pharmacist

Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

Prebiotic Inulin Fiber label
Go deeper

The Full Monographs Behind Prebiotic Inulin Fiber’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Black Psyllium

Interacts with 2,025 drugs

Black psyllium is a soluble-fiber supplement made from the seeds of a Plantago plant, used mostly to ease constipation and support digestive health. It is best known and most studied for rel...

Read the full Black Psyllium monograph → Herb & supplement monograph

Fructo-oligosaccharides (fos)

Fructo-oligosaccharides (FOS) are a type of soluble fiber that acts as a prebiotic, meaning they feed the helpful bacteria in your gut. They are generally considered safe for most people in...

Read the full Fructo-oligosaccharides (fos) monograph →
Sources

Sources & How We Checked

Prebiotic Inulin Fiber's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

The 24 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Black Psyllium 18 references
  1. McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, LLC 1997.
  2. Gruenwald J, Brendler T, Jaenicke C. PDR for Herbal Medicines. 1st ed. Montvale, NJ: Medical Economics Company, Inc., 1998.
  3. Covington TR, et al. Handbook of Nonprescription Drugs. 11th ed. Washington, DC: American Pharmaceutical Association, 1996.
  4. Etman M. Effect of a bulk forming laxative on the bioavailablility of carbamazepine in man. Drug Dev Ind Pharm 1995;21:1901-6.
  5. Perlman BB. Interaction between lithium salts and ispaghula husk. Lancet 1990;335:416.
  6. Vaswani SK, Hamilton RG, Valentine MD, Adkinson NF. Psyllium laxative-induced anaphylaxis, asthma, and rhinitis. Allergy 1996;51:266-8. PubMed
  7. Lantner RR, Espiritu BR, Zumerchik P, Tobin MC. Anaphylaxis following ingestion of a psyllium-containing cereal. JAMA 1990;264:2534-6. DOI
  8. Kaplan MJ. Anaphylactic reaction to "Heartwise." N Engl J Med 1990;323:1072-3. DOI
  9. Nordstrom M, Melander A, Robertsson E, Steen B. Influence of wheat bran and of a bulk-forming ispaghula cathartic on the bioavailability of digoxin in geriatric in-patients. Drug Nutr Interact 1987;5:67-9..
  10. Robinson DS, Benjamin DM, McCormack JJ. Interaction of warfarin and nonsystemic gastrointestinal drugs. Clin Pharmacol Ther 1971;12:491-5. PubMed
  11. Garcia JJ, Fernandez N, Diez MJ, et al. Influence of two dietary fibers in the oral bioavailability and other pharmacokinetic parameters of ethinyloestradiol. Contraception 2000;62:253-7. PubMed
  12. Fernandez N, Lopez C, Díez R, et al. Drug interactions with the dietary fiber Plantago ovata husk. Expert Opin Drug Metab Toxicol 2012;8(11):1377-86.
  13. Semen plantaginis in: WHO Monographs on Selected Medicinal Plants, volume 1. World Health Organization, Geneva, 1999. Available at http://apps.who.int/medicinedocs/en/d/Js2200e/. Accessed November 26, 1026.
  14. Code of Federal Regulations, Title 21 (21CFR 101.17). Food labeling warning, notice, and safe handling statements. Available at www.ecfr.gov/cgi-bin/text-idx?SID=20f647d3b74161501f46564b915b4048&mc=true&node=se21.2.101_117&rgn=div8. Accessed December 3, 2
  15. Code of Federal Regulations, Title 21 (21CFR 201.319). Specific labeling requirements - water-soluble gums, hydrophilic gums, and hydrophilic mucilloids. Available at www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=201.319. Accessed Dece
  16. Diez R, Garcia JJ, Diez MJ, Sierra M, Sahagun AM, Fernandez N. Influence of Plantago ovata husk (dietary fiber) on the bioavailability and other pharmacokinetic parameters of metformin in diabetic rabbits. BMC Complement Altern Med. 2017 Jun 7;17(1):298. PubMed
  17. Chiu AC, Sherman SI. Effects of pharmacological fiber supplements on levothyroxine absorption. Thyroid. 1998;8(8):667-71. PubMed
  18. Merrick C, Madden CA, Capurso NA. A Case of Blunted Orally Disintegrating Olanzapine Effect Due to Coadministered Psyllium. J Clin Psychiatry 2021;82(2):20cr13633. PubMed

See these in context on the Black Psyllium monograph →

Fructo-oligosaccharides (fos) 6 references
  1. Briet F, et al. Symptomatic response to varying levels of fructo-oligosaccharides consumed occasionally or regularly. Eur J Clin Nutr 1995;49:501-7.
  2. Bouhnik Y, Vahedi K, Achour L, et al. Short-chain fructo-oligosaccharide administration dose-dependently increases fecal bifidobacteria in healthy humans. J Nutr 1999;129:113-6. PubMed
  3. Cummings JH, Macfarlane GT, Englyst HN. Prebiotic digestion and fermentation. Am J Clin Nutr 2001;73:415S-420S. PubMed
  4. Souza DDS, Tahan S, Weber TK, Araujo-Filho HB, de Morais MB. Randomized, double-blind, placebo-controlled parallel clinical trial assessing the effect of fructooligosaccharides in infants with constipation. Nutrients. 2018;10(11). pii: E1602. PubMed
  5. Andermann TM, Fouladi F, Tamburini FB, et al. A Fructo-Oligosaccharide Prebiotic Is Well Tolerated in Adults Undergoing Allogeneic Hematopoietic Stem Cell Transplantation: A Phase I Dose-Escalation Trial. Transplant Cell Ther 2021;27(11):932. PubMed
  6. Dou Y, Yu X, Luo Y, Chen B, Ma D, Zhu J. Effect of Fructooligosaccharides Supplementation on the Gut Microbiota in Human: A Systematic Review and Meta-Analysis. Nutrients 2022;14(16):3298. PubMed

See these in context on the Fructo-oligosaccharides (fos) monograph →

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

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