Interactions on record — worth a quick check against your medications. Based on 8 of 12 ingredients. Check your meds →
Dietary supplement

Fiber Smart Ingredients & Drug Interactions

by Renew Life

Fiber Smart label
See full label image
Powder Category: Other Combinations
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 23, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Fiber Smart 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

Fiber Smart is a dietary supplement by Renew Life with 12 active ingredients. Its ingredients are commonly taken for constipation, diarrhea, high cholesterol.Based on those ingredients, 2,185 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Marshmallow, Dietary Fiber, Guar Gum. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

Jump to a section

Check Your Meds Against Fiber Smart by Renew Life

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

Pharmacist-reviewed data Checks every ingredient Answer in seconds
Prefer a human? Send your question to our licensed pharmacists — free, answered by email within 24 hours.

HelloPharmacist Scorecard of Fiber Smart by Renew Life

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 Jul 11, 2026

What’s inside

Low disclosure
Ingredient Transparency · database check
Low

Most active ingredients don't disclose an individual amount — you can't tell how much of each you're getting.

Why this rating?
  • The label discloses an exact amount for 1 of its 13 active ingredients.
  • “Probiotic Blend” is a proprietary blend — the label doesn't break down how much of each component you get.
  • “Fiber Smart Blend” is a proprietary blend — the label gives one combined amount (7,500 mg) without saying how much of each component you get.

Fiber Smart contains 14 ingredients, including two types of dietary fiber (soluble and insoluble) and several other active components. L-glutamine is an amino acid; L. acidophilus and B. bifidum are beneficial bacteria (probiotics); slippery elm, marshmallow, and fennel are herbal ingredients; and guar gum and stevia extract are functional additives.

The product also includes FOS (a prebiotic fiber), triphala (an Ayurvedic blend), B. infantis (another probiotic), organic flax, and a proprietary probiotic blend. There are no inactive fillers or other ingredients listed.

Does it work?

Strong evidence
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
Strong

Clinical evidence supports at least one of this product's ingredients for its stated purpose.

Why this rating?
  • The label markets this product for: digestive wellness and gut health support.
  • We looked for evidence on: Antibiotic-associated diarrhea, Constipation, Diarrhea, Flatulence, Inflammatory bowel disease (IBD), Crohn disease — and 4 related terms.
  • The strongest evidence on file: Black Psyllium is rated "Effective" for Constipation (Natural Medicines).
  • Also on file: Lactobacillus Acidophilus is rated "Possibly Effective" for Antibiotic-associated diarrhea.
  • Also on file: Guar Gum is rated "Possibly Effective" for Constipation.

The evidence base for this product's ingredients varies widely. Guar gum shows the strongest support, with 'Possibly Effective' ratings for high cholesterol, high blood pressure, irritable bowel syndrome, and constipation.

L. acidophilus and B. bifidum are rated 'Possibly Effective' for irritable bowel syndrome, and L. acidophilus is also 'Possibly Effective' for antibiotic-associated diarrhea and bacterial vaginosis. Fennel is 'Possibly Effective' for period pain (dysmenorrhea).

Most other ingredients—slippery elm, marshmallow, triphala, and stevia—lack enough reliable evidence in our data to establish how well they work, rated 'Insufficient Reliable Evidence To Rate.' L-glutamine shows 'Effective' for sickle cell disease and 'Possibly Effective' for some specialized conditions like HIV wasting, but those aren't typical uses for a fiber supplement.

The evidence, ingredient by ingredient Black Psyllium Glutamine Slippery Elm Fennel Marshmallow Lactobacillus Acidophilus Guar Gum Stevia

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 8 of the 9 matched ingredients.
  • Pregnancy & breastfeeding safety ratings cover 9 of 9.
  • General safety write-ups exist for 9 of 9.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Most ingredients in Fiber Smart are generally well tolerated. L-glutamine, L. acidophilus, B. bifidum, slippery elm, marshmallow, guar gum, and stevia extract are all considered well tolerated in healthy adults for short-term use, though long-term human safety data are limited for several of them.

The most common side effects are gastrointestinal: L-glutamine may cause belching, bloating, constipation, nausea, vomiting, or diarrhea; probiotics may cause bloating and flatulence; and guar gum often causes abdominal pain, bloating, diarrhea, and gas. Fennel carries more caution—avoid medicinal or concentrated amounts during pregnancy due to hormone-like effects, and use caution while breastfeeding.

Marshmallow should also be avoided in pregnancy and breastfeeding due to insufficient safety data. L-glutamine is rated 'Likely Safe' in pregnancy but not well studied in breastfeeding.

Guar gum must be taken with plenty of water to avoid choking or blockage, especially at higher doses. L. acidophilus is 'Possibly Safe' in pregnancy; data on B. bifidum pregnancy safety are limited but it's rated 'Possibly Safe.'

Side effects, ingredient by ingredient Black Psyllium Glutamine Slippery Elm Fennel Marshmallow Lactobacillus Acidophilus Guar Gum Stevia

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?
  • 9 of the 9 matched ingredients can interact with medications — Black Psyllium, Fennel, Stevia, Marshmallow, Lactobacillus Acidophilus, among others.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs; seizure medications; diabetes medications; heart-rhythm medications; lithium.
  • For scale: 2,186 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.

Before taking Fiber Smart, check with your pharmacist if you take anticonvulsant medications (used for seizures), antibiotics, birth control pills, blood thinners, heart medications like digoxin, diabetes drugs like metformin, the antibiotic ciprofloxacin, the cancer drug tamoxifen, blood pressure medications, or lithium. The probiotics in this product can be killed by antibiotics, and several ingredients may slow how your body absorbs oral medications—timing your doses apart can help.

Additionally, guar gum may reduce blood sugar or blood pressure further if you're already on medications for these conditions.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFormula with limited ingredient disclosure with clinical evidence supporting its stated purpose. Moderate medication interactions have been identified, and safety information is well characterized.

Fiber Smart is a multi-ingredient fiber and probiotic product best suited for people looking to support digestion and manage IBS or constipation. If you take any prescription medications—especially anticonvulsants, antibiotics, birth control, blood thinners, heart medications, diabetes drugs, or mood stabilizers like lithium—check your exact medications with the tool on this page before starting.

People with liver or kidney disease should talk to their doctor first, and those in pregnancy or breastfeeding should discuss it with their healthcare provider.

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

Assessment coverage: 9 of 13 active ingredients matched to our full ingredient reviews (monographs). Based on the product label dated Mar 24, 2017.

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 Fiber Smart, straight from the product label.

Brand Renew Life
Barcode (UPC) 631257534088
Net contents 8 oz.; 227 Gram(s)
Market status On market
Date entered into DSLD Mar 24, 2017
DSLD ID 71878
Product type Other Combinations
Supplement form Powder
Dietary claims / uses Nutrient, All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years), Gluten 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 Fiber Smart by Renew Life, 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:
7.5 Gram(s)
Maximum serving Sizes:
7.5 Gram(s)
Servings per container
30
UPC/BARCODE
631257534088
IngredientAmount% DV
Calories25 Calorie(s)--
Total Carbohydrates3 Gram(s)1%
L-Glutamine0 NP--
Calories from Fat5 Calorie(s)--
Dietary Fiber2.5 Gram(s)10%
Protein2 Gram(s)4%
Total Fat0.5 Gram(s)1%
Soluble Fiber1 Gram(s)--
Insoluble Fiber1.5 Gram(s)--
L. acidophilus0 NP--
Slippery Elm0 NP--
B. bifidum0 NP--
Fennel0 NP--
FOS0 NP--
Marshmallow0 NP--
Triphala0 NP--
B. infantis0 NP--
Probiotic Blend0 NP--
organic Flax0 NP--
Guar Gum0 NP--
Stevia extract0 NP--
Fiber Smart Blend7500 mg--

Other ingredients: None

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.
General Statements

Digestive wellness, naturally

For nearly two decades, we have pioneered superior-quality digestive care supplements to help people achieve optimal health from the inside out.

Advanced fiber for sensitive digestion

For sensitive colons ~ Promotes regularity ~ Supports intestinal health ~ Pleasant taste & gluten free

Quality, purity, and potency guaranteed through expiration.

Packed by weight, not volume. Contents may settle during storage and handling.

Manufactured in USA in a GMP facility.

90019D

Brand IP Statement(s)

At Renew Life, we believe a healthy gut is a happy gut.

Get your daily fiber fix and more with Fiber Smart.

Formula

This high-fiber supplement is ideal for those with sensitive digestion, occasional gas, bloating, and constipation.

Includes L-glutamine, probiotics, and soothing herbs to help boost digestive balance and intestinal health.

Flax Probiotics L-Glutamine

This product may contain mild traces of milk proteins from fermentation ingredients.

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.

FDA Statement of Identity

Fiber Supplement

Suggested/Recommended/Usage/Directions

Directions: Take one scoop in 8 ounces of water or juice. Drink plenty of water while using this product.

Precautions

This product may contain mild traces of milk proteins from fermentation ingredients.

Keep out of reach of children.

Consult your healthcare professional before using this or any product if you are pregnant, nursing, trying to conceive, taking medication, or have a medical condition.

Notice: Using this supplement without at least a full glass of liquid may cause choking. Do not use this supplement if you have difficulty in swallowing, acute cough, or obstructed bowel.

Tamper Evident: Do not use if safety seal is broken or missing.

Formulation

Gluten free Soy free No artificial ingredients

Storage

Store in a dry place at 59-86(0)F (15-30(0)C).

General

#15631 030316

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

See for yourself

Fiber Smart by Renew Life label

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

Fiber Smart 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 Fiber Smart by Renew Life

These are the 12 active ingredients this product is made of. Select any to open its full monograph.

Serving size7.5 Gram(s) Dosage formPowder Servings per container30 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
2.5 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
  • › Soluble Fiber
  • › Insoluble Fiber

Protein

2 Gram(s) per serving

Fiber Smart Blend

7500 mg per serving

Other (inactive) ingredients: None. These complete the product’s ingredient list but are not active constituents.

Interaction report

Fiber Smart by Renew Life Drug Interactions

Want to check YOUR meds against Fiber Smart?

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
2,185Drugs
2,153 Moderate 32 Minor

Ingredients driving the most interactions

Marshmallow 2,040
Dietary Fiber 2,025
Guar Gum 2,025
Slippery Elm 2,022
Fennel 740

Individual Drug Interactions

The ingredients in Fiber Smart interact with 2,185 drugs. Click any drug to see the details.

8 of the 12 ingredients in Fiber Smart interact with drugs. Each result below shows which ingredient is responsible. Marshmallow Dietary Fiber Guar Gum Slippery Elm Fennel Stevia extract Probiotic Blend L-Glutamine

Each ingredient & the kinds of drugs it affects

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

Marshmallow3 drug types · 2,040 drugs

Lithium

Theoretically, due to potential diuretic effects, marshmallow might reduce excretion and increase levels of lithium.
Marshmallow is thought to have diuretic properties. To avoid lithium toxicity, the dose of lithium might need to be decreased when used with marshmallow.

Likelihood Probable Evidence D
Anticoagulant/Antiplatelet Drugs

Theoretically, marshmallow flower might have antiplatelet effects.
Animal research suggests that marshmallow flower extract has antiplatelet effects. However, the root and leaf of marshmallow, not the flower, are the plant parts most commonly found in dietary supplements. Theoretically, use of marshmallow flower with anticoagulant/antiplatelet drugs can have additive effects, and might increase the risk for bleeding in some patients.

Likelihood Unlikely Evidence D
Oral Drugs

Theoretically, mucilage in marshmallow might impair absorption of oral drugs.
Marshmallow contains mucilage which can affect oral drug absorption. To avoid changes in absorption, take marshmallow 30-60 minutes after oral medications.

Likelihood Possible Evidence D
Marshmallow full monograph & interactions

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

Guar Gum5 drug types · 2,025 drugs

Ethinyl Estradiol

Theoretically, guar gum might reduce the absorption of ethinyl estradiol, potentially decreasing its effectiveness.
Animal research shows that taking guar gum with ethinyl estradiol decreases ethinyl estradiol absorption. However, this effect has not been reported in humans.

Likelihood Possible Evidence D
Metformin (Glucophage)

Guar gum might reduce the absorption of metformin, potentially decreasing its effectiveness.
A small study in healthy volunteers shows that guar gum reduces the absorption rate of metformin.

Likelihood Probable Evidence B
Oral Drugs

Guar gum might reduce the absorption of some oral drugs, potentially decreasing their effectiveness.
Clinical research shows that guar gum reduces or slows absorption of medications such as penicillin and metformin. To avoid changes in absorption, take guar gum 30-60 minutes after oral medications.

Likelihood Possible Evidence B
Penicillin

Guar gum might reduce the absorption of penicillin, potentially decreasing its effectiveness.
A small clinical study in healthy volunteers shows that taking guar gum with penicillin results in decreased penicillin absorption and reduced penicillin levels.

Likelihood Probable Evidence B
Digoxin (Lanoxin)

Guar gum might slow digoxin absorption, but it does not seem to impact how much digoxin is absorbed overall.
Two small studies in healthy volunteers show no change in the overall extent of digoxin absorption, although early absorption was slowed, when taken with guar gum.

Likelihood Possible Evidence B
Guar Gum full monograph & interactions

Slippery Elm1 drug type · 2,022 drugs

Oral Drugs

Theoretically, slippery elm may slow the absorption and reduce serum levels of oral drugs.
Slippery elm inner bark contains mucilage, which may interfere with the absorption of orally administered drugs.

Likelihood Possible Evidence D
Slippery Elm full monograph & interactions

Fennel6 drug types · 740 drugs

Anticoagulant/Antiplatelet Drugs

Theoretically, fennel might increase the risk of bleeding when used with antiplatelet or anticoagulant drugs.

Animal research suggests that fennel oil has antithrombotic and antiplatelet effects.

Likelihood Possible Evidence D
Ciprofloxacin (Cipro)

Theoretically, fennel might decrease the levels and clinical effects of ciprofloxacin.

Animal research shows that fennel reduces ciprofloxacin bioavailability by nearly 50%, possibly due to the metal cations such as calcium, iron, and magnesium contained in fennel. This study also found that fennel increased tissue distribution and slowed elimination of ciprofloxacin.

Likelihood Probable Evidence D
Contraceptive Drugs

Theoretically, taking large amounts of fennel might decrease the effects of contraceptive drugs due to competition for estrogen receptors.

Some constituents of fennel have estrogenic activity.

Likelihood Possible Evidence D
Cytochrome P450 3A4 (Cyp3A4) Substrates

Theoretically, fennel might increase levels of drugs metabolized by CYP3A4.

In vitro research suggests that fennel inhibits CYP3A4 enzyme activity. This effect has not been reported in humans.

Likelihood Possible Evidence D
Estrogens

Theoretically, taking large amounts of fennel might interfere with hormone replacement therapy due to competition for estrogen receptors.

Some constituents of fennel have estrogenic activity.

Likelihood Possible Evidence D
Tamoxifen (Nolvadex)

Theoretically, taking large amounts of fennel might decrease the antiestrogenic effect of tamoxifen.

Some constituents of fennel have estrogenic activity, which may interfere with the antiestrogenic activity of tamoxifen.

Likelihood Possible Evidence D
Fennel full monograph & interactions

Stevia extract3 drug types · 259 drugs

Lithium

Theoretically, stevia might decrease clearance and increase levels of lithium.
Animal research suggests that stevia extracts might have diuretic activity. Theoretically, increased reabsorption of lithium along with sodium might reduce excretion and increase levels of lithium.

Likelihood Possible Evidence D
Antidiabetes Drugs

Theoretically, stevia might increase the risk for hypoglycemia when combined with antidiabetes drugs.
Preliminary clinical research in patients with type 2 diabetes suggests that taking a single dose of stevia extract 1000 mg reduces postprandial blood glucose levels when taken with a meal. However, other clinical research in patients with type 1 or type 2 diabetes suggests that taking stevioside 250 mg three times daily does not significantly affect blood glucose levels or glycated hemoglobin (HbA1C) after three months of treatment.

Likelihood Possible Evidence D
Antihypertensive Drugs

Theoretically, combining stevia or stevia constituents with antihypertensive agents might increase the risk of hypotension.
Stevia extract and stevioside might lower blood pressure in patients with hypertension. However, other clinical research suggests that stevioside does not significantly lower blood pressure in patients with hypertension.

Likelihood Possible Evidence D
Stevia extract full monograph & interactions

Probiotic Blend1 drug type · 182 drugs

Antibiotic Drugs

Theoretically, taking Lactobacillus acidophilus with antibiotic drugs might decrease the effectiveness of L. acidophilus.
L. acidophilus preparations usually contain live and active organisms. Therefore, simultaneously taking antibiotics might kill a significant number of the organisms. Tell patients to separate administration of antibiotics and L. acidophilus preparations by at least two hours.

Likelihood Probable Evidence D
Probiotic Blend full monograph & interactions

L-Glutamine1 drug type · 50 drugs

Anticonvulsants

Theoretically, glutamine might antagonize the effects of anticonvulsant medications.
Glutamine is metabolized to the excitatory neurotransmitter glutamate. Glutamate might have antagonistic effects with anticonvulsant drugs. However, this interaction has not yet been reported in humans.

Likelihood Possible Evidence D
L-Glutamine full monograph & interactions
The maker

Brand information

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

Renew Life

Name
Renew Life Formulas
City
Palm Harbor
State
FL
ZipCode
34683
Phone Number
1-800-830-1800
Web Address
www.renewlife.com
Pharmacist Counseling Corner

Fiber Smart by Renew Life: Common Questions

Does Fiber Smart by Renew Life interact with any medications?
Yes. Based on its ingredients, Fiber Smart has a known interaction with 2,185 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Fiber Smart contains 12 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.
Can I take Fiber Smart if I'm on antibiotics?
Not at the same time. The live probiotic organisms in Fiber Smart (L. acidophilus and B. bifidum) can be killed by antibiotics, which defeats their purpose. Separate doses by at least a few hours—ask your pharmacist for the best timing specific to your antibiotic.
Is Fiber Smart safe during pregnancy?
Most ingredients lack enough pregnancy safety data, and fennel should be avoided in pregnancy due to hormone-like effects. Marshmallow is also best avoided in pregnancy. Talk to your doctor or midwife before taking this product while pregnant.
What are the most common side effects?
Gastrointestinal symptoms are most common: bloating, gas, constipation, diarrhea, nausea, and abdominal discomfort. These often improve as your body adjusts. Start with a smaller dose and increase gradually to minimize these effects.
Should I take Fiber Smart with my other medications?
No—several ingredients in Fiber Smart can reduce how much of your oral medications your body absorbs. Take Fiber Smart at least 30–60 minutes after your other medications. Check the medication checker on this page for your specific drugs.
Is this product safe for people with weakened immune systems?
The probiotics in Fiber Smart should be used cautiously by people with weakened immune systems. While generally considered low risk, there are rare reports of probiotic infections in critically ill patients. Check with your doctor first.
Does Fiber Smart help with IBS?
Several ingredients—guar gum, L. acidophilus, and B. bifidum—are rated 'Possibly Effective' for IBS in our data. However, evidence is preliminary, and results vary from person to person. Talk to your doctor about whether it's right for your symptoms.

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

Not sure if Fiber Smart is safe with your meds?

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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.

Fiber Smart label
Go deeper

The Full Monographs Behind Fiber Smart’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

Glutamine

Interacts with 50 drugs

Glutamine is the most abundant amino acid in the body and is usually made in your muscles. A prescription form is FDA-approved to help reduce sickle cell disease complications, but for most...

Read the full Glutamine monograph → Herb & supplement monograph

Slippery Elm

Interacts with 2,022 drugs

Slippery elm is a traditional herbal remedy made from the inner bark of a North American elm tree, used mainly to soothe sore throats and irritated digestive tracts. Its mucilage can coat an...

Read the full Slippery Elm monograph → Herb & supplement monograph

Fennel

Interacts with 740 drugs

Fennel is a Mediterranean herb widely used as a food and spice, and traditionally taken for digestive complaints, colic, and menstrual cramps. Some small studies suggest possible benefit for...

Read the full Fennel monograph → Herb & supplement monograph

Marshmallow

Interacts with 2,040 drugs

Marshmallow root is a traditional herb rich in soothing, gel-like fibers called mucilage, which is why it has long been used for coughs, sore throats, and stomach irritation. Evidence for th...

Read the full Marshmallow monograph → Herb & supplement monograph

Lactobacillus Acidophilus

Interacts with 182 drugs

Lactobacillus acidophilus is a 'friendly' bacterium used as a probiotic to support gut and vaginal health. It is generally well tolerated in healthy people, and there is reasonable evidence...

Read the full Lactobacillus Acidophilus monograph → Herb & supplement monograph

Guar Gum

Interacts with 2,025 drugs

Guar gum is a soluble, gel-forming fiber from the guar bean that may modestly help with cholesterol, blood sugar, and bowel regularity. It is generally safe in food amounts, but concentrated...

Read the full Guar Gum monograph → Herb & supplement monograph

Stevia

Interacts with 259 drugs

Stevia is a plant-based, calorie-free sweetener that is widely used as a sugar alternative and is considered safe in normal food amounts by major regulators. Purified stevia extracts have a...

Read the full Stevia monograph →
Sources

Sources & How We Checked

Fiber Smart'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 112 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.

Glutamine 11 references
  1. Miller AL. Therapeutic considerations of L-glutamine: a review of the literature. Altern Med Rev 1999;4:239-48..
  2. Bozzetti F, Biganzoli L, Gavazzi C, et al. Glutamine supplementation in cancer patients receiving chemotherapy: a double-blind randomized study. Nutrition 1997;13:748-51.. PubMed
  3. Mebane AH. L-Glutamine and mania. Am J Psychiatry 984;141:1302-3.
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Black Psyllium 18 references
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Lactobacillus Acidophilus 15 references
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Slippery Elm 3 references
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Bifidobacterium Bifidum 7 references
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  5. Badehnoosh B, Karamali M, Zarrati M, et al. The effects of probiotic supplementation on biomarkers of inflammation, oxidative stress and pregnancy outcomes in gestational diabetes. J Matern Fetal Neonatal Med. 2018 May;31(9):1128-1136.
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See these in context on the Bifidobacterium Bifidum monograph →

Fennel 17 references
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See these in context on the Fennel monograph →

Marshmallow 5 references
  1. Monographs on the medicinal uses of plant drugs. Exeter, UK: European Scientific Co-op Phytother, 1997.
  2. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Food, Drugs and Cosmetics. 2nd ed. New York, NY: John Wiley & Sons, 1996.
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See these in context on the Marshmallow monograph →

Guar Gum 26 references
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Stevia 10 references
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  2. Melis MS. A crude extract of Stevia rebaudiana increases the renal plasma flow of normal and hypertensive rats. Braz J Med Biol Res 1996;29:669-75.
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See these in context on the Stevia monograph →

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