Drug & supplement interaction

Glucomannan + Levodopa, Carbidopa

Levodopa, Carbidopa brand name: Duodopa.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 20, 2026
The bottom line No known interaction

We found no known interaction between Glucomannan and Levodopa, Carbidopa in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, there is a timing consideration — Glucomannan can reduce how much Levodopa, Carbidopa you absorb if they are taken together, so they should be spaced apart, and the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Glucomannan and Levodopa, Carbidopa

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Levodopa, Carbidopa and Glucomannan in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Glucomannan safety at a glance

Glucomannan overall Use caution Generally well tolerated when taken with plenty of water, but it can cause choking or blockage if not swallowed properly.
Pregnancy Use caution Not enough reliable safety data; talk to your doctor before using during pregnancy.
Breastfeeding Use caution Little is known about its safety while breastfeeding, so caution is advised.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Levodopa, Carbidopa and Glucomannan? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Levodopa, Carbidopa

Interactions in our licensed database are recorded against drug classes, not just single drug names. Levodopa, Carbidopa is filed under 5 classifications — including dopamine agonists, seizure threshold lowering drugs. Glucomannan has documented interactions with 1 drug class — the most serious being oral drugs (moderate) — and none of Levodopa, Carbidopa’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Glucomannan Does Interact With Other Medications

Glucomannan has 2,022 moderate known drug interactions in our database — Levodopa, Carbidopa isn’t one of them. If you take anything else, check it against the full list below.

Moderate 2,022 No known interaction 808 (incl. Levodopa, Carbidopa)
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.

What to actually watch for

No Interaction Found — But Data Suggests Glucomannan and Levodopa, Carbidopa May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do.

  • Bloating or gas / Constipation / Stomach pain / Diarrhea / Vomiting / Nausea Additional detail

    Glucomannan

    “Orally, glucomannan can cause gastrointestinal disturbances, including abdominal pain, bloating, constipation, diarrhea, flatulence, nausea, and vomiting, especially when taken in doses of more than 3 grams daily. Esophageal and gastrointestinal obstructions have been reported when dry glucomannan-containing products are taken with insufficient fluid.”

    Glucomannan · Natural Medicines adverse-effect record, reported in constipation.

    6 sources cited
    1. 57781. Yoshida, M., Vanstone, C. A., Parsons, W. D., Zawistowski, J., and Jones, P. J. Effect of plant sterols and glucomannan on lipids in individuals with and without type II diabetes. Eur.J Clin Nutr. 2006;60(4):529-537. PubMed
    2. 57784. Wood, R. J., Fernandez, M. L., Sharman, M. J., Silvestre, R., Greene, C. M., Zern, T. L., Shrestha, S., Judelson, D. A., Gomez, A. L., Kraemer, W. J., and Volek, J. S. Effects of a carbohydrate-restricted diet with and without supplemental soluble fiber
    3. 92004. Carabin IG, Lyon MR, Wood S, et al. Supplementation of the diet with the functional fiber PolyGlycoplex is well tolerated by healthy subjects in a clinical trial. Nutr J 2009;8:9. PubMed
    4. 92010. Lyon MR, Reichert RG. The effect of a novel viscous polysaccharide along with lifestyle changes on short-term weight loss and associated risk factors in overweight and obese adults: an observational retrospective clinical program analysis. Altern Med Rev
    5. 92011. Lyon M, Wood S, Pelletier X, et al. Effects of a 3-month supplementation with a novel soluble highly viscous polysaccharide on anthropometry and blood lipids in nondieting overweight or obese adults. J Hum Nutr Diet 2011;24(4):351-9. PubMed
    6. 97935. Han Y, Zhang L, Liu XQ, Zhao ZJ, Lv LX. Effect of glucomannan on functional constipation in children: a systematic review and meta-analysis of randomised controlled trials. Asia Pac J Clin Nutr 2017;26(3):471-7.

    Levodopa, Carbidopa

    Listed in the ADVERSE REACTIONS section of the FDA label for Levodopa, Carbidopa. Read the label on DailyMed ›

  • Stomach upset Additional detail

    Glucomannan

    Recorded for Glucomannan in the same Natural Medicines adverse-effect record shown under Bloating or gas / Constipation / Stomach pain / Diarrhea / Vomiting / Nausea above.

    Levodopa, Carbidopa

    Listed in the ADVERSE REACTIONS section of the FDA label for Levodopa, Carbidopa. Read the label on DailyMed ›

Reported for Glucomannan but not commonly for Levodopa, Carbidopa: liver problems and wheezing.

Effects for Levodopa, Carbidopa come from the ADVERSE REACTIONS section of its FDA label; effects for Glucomannan come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Timing matters

No Interaction — But Take Glucomannan and Levodopa, Carbidopa a Few Hours Apart

Levodopa, Carbidopa is a Parkinson's medication, and it is absorbed best on its own. Glucomannan can bind to it in the stomach so that less of the medicine reaches your bloodstream. That is not an interaction in the usual sense — nothing harmful happens when they meet — but taken at the same time, your dose can effectively become a smaller one.

The fix is simple: separate the two by about 4 hours. Take Levodopa, Carbidopa first, on its own, and keep Glucomannan for later in the day.

Where this comes from: this is HelloPharmacist editorial guidance, not a licensed interaction record — it applies established absorption pharmacology to Parkinson's medications, whose FDA labels state a separation requirement of their own. Reviewed by the HelloPharmacist pharmacy team. If you already take them together, do not change your medicine on your own; ask your pharmacist how to space them.

Everything else you take

See Every Supplement That Interacts With Levodopa, Carbidopa

This page covers Glucomannan only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Levodopa, Carbidopa page lists 26 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Branched-chain Amino Acids (bcaa) (major), Cowhage (major), Indian Snakeroot (major), Magnesium (major) and Phenylalanine (major).

By severity: 7 major · 17 moderate · 2 minor.

From our pharmacist’s overview on the Levodopa, Carbidopa page

“Cowhage is the first thing to know here. It naturally contains levodopa, sometimes 75 to 400 mg per dose, so stacking it on Levodopa, Carbidopa (Duodopa) risks levodopa excess.”

Reviewed by 2 · Jul 18, 2026

Open the Levodopa, Carbidopa 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. Even though Glucomannan itself has no known interaction with Levodopa, Carbidopa, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Glucomannan and Levodopa, Carbidopa 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%

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

29 days ago today
Medication Levodopa, Carbidopa
Top 25%

#622 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.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Glucomannan reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Glucomannan and Levodopa, Carbidopa records this page draws on were last updated July 10, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
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.

Amorphophallus konjac · Araceae · Root (tuber/corm) · Capsules, tablets, powder, drink mixes; also used as a food ingredient (konjac noodles, shirataki noodles)

An interaction check asks whether these two react with each other — it does not ask whether Glucomannan is a good idea for someone in your situation. Here is what our Glucomannan record says about it on its own.

Glucomannan: dosing

There is no single official standardized dose of glucomannan, and the right amount can vary by product and purpose. Because it is a concentrated fiber, the way you take it matters as much as the amount.The best advice is to follow the directions on the product label and to take each dose with a full glass of water (and drink fluids throughout the day).

From our Glucomannan monograph — the full record covers uses, side effects and every documented interaction.

Read the full Glucomannan monograph & all interactions
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
2,022Moderate
0Minor
807No known interaction
2,022 Moderate 807 No interaction
Moderate

2,022 interactions

Showing 60 of 2,022 moderate interactions — see all 2,022 on the Glucomannan page.

No interaction 807 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 807 medications checked with no known interaction — see the full Glucomannan list.

See the full Glucomannan interactions page
See every supplement checked against Levodopa, Carbidopa, ranked by severity
Evidence & sources

Glucomannan References

The 15 references that drive our Glucomannan monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Henry DA, Mitchell AS, Aylward J, et al. Glucomannan and risk of oesophageal obstruction. Br Med J 1986;292:591-2. PubMed
  2. 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
  3. Villaverde, A. F., Benlloch, S., Berenguer, M., Miguel, Rayon J., Pina, R., and Berenguer, J. Acute hepatitis of cholestatic type possibly associated with the use of glucomannan (amorphophalus konjac). J Hepatol. 2004;41(6):1061-1062. PubMed
  4. Yoshida, M., Vanstone, C. A., Parsons, W. D., Zawistowski, J., and Jones, P. J. Effect of plant sterols and glucomannan on lipids in individuals with and without type II diabetes. Eur.J Clin Nutr. 2006;60(4):529-537. PubMed
  5. Wood, R. J., Fernandez, M. L., Sharman, M. J., Silvestre, R., Greene, C. M., Zern, T. L., Shrestha, S., Judelson, D. A., Gomez, A. L., Kraemer, W. J., and Volek, J. S. Effects of a carbohydrate-restricted diet with and without supplemental soluble fiber
  6. Vanderbeek, P. B., Fasano, C., O'Malley, G., and Hornstein, J. Esophageal obstruction from a hygroscopic pharmacobezoar containing glucomannan. Clin Toxicol.(Phila) 2007;45(1):80-82. PubMed
  7. Bernstein, J. A., Crandall, M. S., and Floyd, R. Respiratory sensitization of a food manufacturing worker to konjac glucomannan. J Asthma 2007;44(8):675-680. PubMed
  8. Shichijo, K., Kobayashi, Y., Fueki, R., Shimoyama, K., and Masaya, M. [2 cases of konjac bronchial asthma found outside the "konnyaku" producing district]. Arerugi 1969;18(2):97-100.
  9. Carabin IG, Lyon MR, Wood S, et al. Supplementation of the diet with the functional fiber PolyGlycoplex is well tolerated by healthy subjects in a clinical trial. Nutr J 2009;8:9. PubMed
  10. Lyon MR, Reichert RG. The effect of a novel viscous polysaccharide along with lifestyle changes on short-term weight loss and associated risk factors in overweight and obese adults: an observational retrospective clinical program analysis. Altern Med Rev
  11. Lyon M, Wood S, Pelletier X, et al. Effects of a 3-month supplementation with a novel soluble highly viscous polysaccharide on anthropometry and blood lipids in nondieting overweight or obese adults. J Hum Nutr Diet 2011;24(4):351-9. PubMed
  12. Han Y, Zhang L, Liu XQ, Zhao ZJ, Lv LX. Effect of glucomannan on functional constipation in children: a systematic review and meta-analysis of randomised controlled trials. Asia Pac J Clin Nutr 2017;26(3):471-7.
  13. Health Canada Safety Alert. Health Canada Advises Canadians that natural health products containing glucomannan may cause serious choking if used with insufficient fluid. January 29, 2010. Alert # RA-110003825. https://healthycanadians.gc.ca/recall-alert-
  14. Mortensen A, Aguilar F, Crebelli, et al. EFSA Panel on Food Additives and Nutrient Sources added to Food. Re-evaluation of konjac gum (E 425 i) and konjac glucomannan (E425 ii) as food additives. EFSA Journal 2017;15(6):4864.
  15. 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

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Glucomannan and Levodopa, Carbidopa Together: Common Questions

Is it safe to take Glucomannan with Levodopa, Carbidopa?
We do not list a known interaction between Glucomannan and Levodopa, Carbidopa. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Do Glucomannan and Levodopa, Carbidopa have any of the same side effects?
Yes — our sources link each of them separately to 7 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
How far apart should I space Glucomannan and Levodopa, Carbidopa?
Glucomannan can bind Levodopa, Carbidopa in the gut and reduce how much of it you absorb, so they should not be swallowed together. The separation this page recommends is in the timing section above. Spacing them is about absorption — it is not a warning that they react with each other.
How was the Glucomannan and Levodopa, Carbidopa combination checked?
Interactions in our licensed database are recorded against drug classes. Levodopa, Carbidopa is filed under 5 classifications, and Glucomannan has documented interactions with 1 drug class — none of Levodopa, Carbidopa's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Glucomannan interact with any other medications?
Yes. Glucomannan has 2,022 documented drug interactions in our database — Levodopa, Carbidopa is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Levodopa, Carbidopa interact with any supplements?
Yes. Levodopa, Carbidopa has documented interactions with 26 supplements in our database — Glucomannan is not one of them. The Levodopa, Carbidopa interaction page linked on this page lists every one, ranked by severity.

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

Where next

Keep Exploring

Glucomannan monograph Uses, safety profile, and every drug interaction in one place Levodopa, Carbidopa supplement interactions Every supplement checked against Levodopa, Carbidopa, ranked by severity Supplement interaction checker Check any supplement or product against your medications Browse medications A–Z Every drug we’ve checked against herbs & supplements References The 15 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

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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.