Drug & supplement interaction

Glucomannan + Oxybutynin

Oxybutynin brand names: Ditropan, Ditropan XL, Oxybutynin, Oxytrol, Anturol, and others.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Glucomannan has a moderate interaction with Oxybutynin. Theoretically, glucomannan may decrease absorption of drugs taken orally.

Read the full interaction report
SeverityModerate
LikelihoodProbable
EvidenceB
What do Severity, Likelihood & Evidence mean?
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Interaction report

Glucomannan and Oxybutynin

Here is the interaction we found between these two, with the evidence behind it.

Moderate

ORAL DRUGS

Why this applies to Oxybutynin

Oxybutynin falls under ORAL DRUGS — the group Glucomannan interacts with.

Theoretically, glucomannan may decrease absorption of drugs taken orally.
Due to its viscosity and bulking effects, there is concern that glucomannan can decrease the absorption of oral drugs. A small clinical study in healthy volunteers shows that taking glyburide 2.5 mg plus glucomannan 3.9 grams with breakfast reduces plasma levels of glyburide when compared with breakfast and glyburide alone. In addition, animal research demonstrates this effect on amoxicillin, but shows increased absorption of metronidazole. This mouse model also demonstrates that metronidazole elimination is prolonged, but amoxicillin elimination is enhanced by 38%; glucomannan may also affect the distribution of some drugs. To avoid changes in absorption, take glucomannan 30-60 minutes after taking oral drugs.
Severity Moderate Likelihood Probable Evidence B

Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the simple version: glucomannan is a thick soluble fiber that turns into a gel in your gut. That gel can physically grab onto pills and slow or reduce how much your body soaks up. With oxybutynin, the worry is that less drug gets absorbed, which could mean your bladder control medicine doesn't work as well. You might notice more of the symptoms you're trying to treat, like urgency, frequent trips to the bathroom, or leaks.

This is mostly a timing issue, and the evidence is fairly modest. An easy fix is to space them out: take your oxybutynin first, then wait about 30 to 60 minutes before your glucomannan. Always take the fiber with plenty of water. Before you combine them, it's worth a quick chat with your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Shima K, Tanaka A, Ikegami H, et al. Effect of dietary fiber, glucomannan, on absorption of sulfonylurea in man. Horm Metab Res 1983;15:1-3. PubMed
  2. Zhang Y, Aldamarany WAS, Song G, et al. Influence of konjac glucomannan and its derivatives on the oral pharmacokinetics of antimicrobial agent in antibiotics cocktails: Keep vigilant on dietary fiber supplement. Int J Biol Macromol 2023;251:126306. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Glucomannan Also Interacts With Other Medications

Glucomannan has 2,021 moderate known drug interactions in our database — the Oxybutynin one above is one of them. If you take anything else, check it against the full list below.

Moderate 2,021 No known interaction 809 (incl. Oxybutynin)
Taking anything else?

Check Another of Your Medications Against Glucomannan

Covers the 2,830 medications we’ve checked against Glucomannan. Pick one to open its full report.

From our Q&A

Questions About Glucomannan or Oxybutynin

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Glucomannan or Oxybutynin, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Oxybutynin

This page covers Glucomannan only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Oxybutynin page lists 165 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Grapefruit (major), Henbane (major), Scopolia (major) and St. John's Wort (major).

By severity: 5 major · 116 moderate · 44 minor.

From our pharmacist’s overview on the Oxybutynin page

“Oxybutynin (Ditropan, Oxytrol, Gelnique) is an anticholinergic for overactive bladder, and its supplement interactions deserve genuine care rather than a quick skim. Most of the list comes down to drug levels: grapefruit juice can push oxybutynin higher and intensify its side effects, while St.”

Reviewed by 2 · Jul 18, 2026

Open the Oxybutynin interaction page

One more smart check

Taking Glucomannan as Part of a Dietary Supplement Product? Check It for Interactions

We hold 467 real supplement products containing Glucomannan, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Glucomannan. Your product may carry other ingredients that interact with Oxybutynin too, on top of Glucomannan — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Glucomannan and Oxybutynin Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Glucomannan
Top 25%

#276 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Oxybutynin
Steady interest

#1,780 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Glucomannan

What is Glucomannan?

Glucomannan
  • Weight loss and appetite control
  • Constipation
  • High cholesterol
  • Blood sugar support
  • Digestive health

Glucomannan is a soluble fiber from the konjac root that swells into a gel in your stomach, which may help with mild weight loss, constipation, and modestly lowering cholesterol. It is generally well tolerated when taken with plenty of water, but it must be taken carefully because it can swell and cause choking or blockage if not swallowed properly. Talk with your pharmacist or doctor before starting it, especially if you have a health condition or take medicines.

Read the full Glucomannan monograph & all interactions
Medication

About Oxybutynin

What Is Oxybutynin Used For?

Brand names: Ditropan, Ditropan XL, Oxybutynin, Oxytrol, Anturol, Gelnique

Oxybutynin treats overactive bladder — including the sudden urge to urinate, leaking before you can reach the bathroom (urge incontinence), and going too frequently. Extended-release tablets (Oxybutynin Chloride) and immediate-release tablets and oral solution (Oxybutynin Chloride) are used for these symptoms. Oxytrol is approved for overactive bladder in men; Oxytrol for Women is approved for overactive bladder in women aged 18 and older.

Extended-release tablets (Oxybutynin Chloride) are also approved for children 6 years and older who have bladder overactivity caused by a neurological condition, such as spina bifida. Immediate-release tablets and oral solution (Oxybutynin Chloride) are indicated for bladder instability symptoms — including urgency, frequency, urinary leakage, and painful urination — in patients with neurogenic bladder conditions.

See full Oxybutynin drug information
Keep checking

Other Drugs & Glucomannan

Browse every other medication we’ve checked against Glucomannan — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
2,021Moderate
0Minor
808No known interaction
2,021 Moderate 808 No interaction
Moderate

2,021 interactions

Showing 60 of 2,021 moderate interactions — see all 2,021 on the Glucomannan page.

No interaction 808 drugs checked — show the list

We also checked Glucomannan against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 808 medications checked with no known interaction — see the full Glucomannan list.

See the full Glucomannan interactions page
See every supplement checked against Oxybutynin, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

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

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

Keep exploring
Glucomannan monograph › Uses, safety, and every drug interaction in one place Oxybutynin supplement interactions › Every supplement checked against Oxybutynin, ranked by severity Oxybutynin drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Glucomannan and Oxybutynin Together: Common Questions

Can you take Glucomannan with Oxybutynin?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Glucomannan and Oxybutynin interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

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

Still Have a Question About Oxybutynin and Glucomannan?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.