Drug & supplement interaction

Carrageenan + Ondansetron

Ondansetron brand name: Zofran.

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 Carrageenan and Ondansetron 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.

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Interaction report

Carrageenan and Ondansetron

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 Ondansetron and Carrageenan 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.

Carrageenan safety at a glance

Carrageenan overall Use caution Food-grade carrageenan is widely used, but its value and safety as a supplement is uncertain and degraded forms may irritate the gut.
Pregnancy Likely Safe When used in food amounts. There is insufficient reliable information available about the safety of using larger amounts; avoid using. Read the full pregnancy detail
Breastfeeding Likely Safe When used in food amounts. There is insufficient reliable information available about the safety of using larger amounts; avoid using. Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Ondansetron and Carrageenan? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Ondansetron

Interactions in our licensed database are recorded against drug classes, not just single drug names. Ondansetron is filed under 7 classifications — including serotonergic drugs, serotonergic drugs, cytochrome p450 1a2 (cyp1a2) substrates. Carrageenan has documented interactions with 1 drug class — the most serious being anticoagulant/antiplatelet drugs (moderate) — and none of Ondansetron’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

Carrageenan Does Interact With Other Medications

Carrageenan has 122 moderate known drug interactions in our database — Ondansetron isn’t one of them. If you take anything else, check it against the full list below.

Moderate 122 No known interaction 2,708 (incl. Ondansetron)
Taking anything else?

Check Another of Your Medications Against Carrageenan

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

What to actually watch for

What Carrageenan Itself Has Been Linked To

This is not an interaction — nothing below involves Ondansetron. It is the side-effect record for Carrageenan on its own, from the licensed Natural Medicines monograph. If something new turns up after you add Carrageenan, this list is the first place to look. One entry is worth acting on rather than waiting out — marked below.

  • Bleeding or bruising Worth acting on Additional detail

    “In one clinical study in males, carrageenan gel applied topically to the penis and anus prior to anal intercourse was reported to cause rectal bleeding that was not directly related to anal intercourse in 8% of patients, compared with 0% of patients using placebo.”

    Carrageenan · Natural Medicines adverse-effect record, reported in bleeding.

    1 source cited
    1. 107851. Laurie C, El-Zein M, Tota JE, et al. Efficacy of a carrageenan gel in preventing anal human papillomavirus (HPV) infection: interim analysis of the Lubricant Investigation in Men to Inhibit Transmission of HPV Infection (LIMIT-HPV) randomised controlled t
  • Itching Additional detail

    “Intravaginally, carrageenan gel has been associated with mild vaginal itching and burning, a vaginal abrasion, bladder fullness, and urinary hesitancy. However, it is unclear if carrageenan was the causal factor of these symptoms.”

    Carrageenan · Natural Medicines adverse-effect record, reported in pruritus.

    2 sources cited
    1. 40044. Coggins, C., Blanchard, K., Alvarez, F., Brache, V., Weisberg, E., Kilmarx, P. H., Lacarra, M., Massai, R., Mishell, D., Jr., Salvatierra, A., Witwatwongwana, P., Elias, C., and Ellertson, C. Preliminary safety and acceptability of a carrageenan gel for
    2. 40068. Elias, C. J., Coggins, C., Alvarez, F., Brache, V., Fraser, I. S., Lacarra, M., Lahteenmaki, P., Massai, R., Mishell, D. R., Jr., Phillips, D. M., and Salvatierra, A. M. Colposcopic evaluation of a vaginal gel formulation of iota-carrageenan. Contracepti PubMed

Everything above comes from the Natural Medicines adverse-effect record for Carrageenan — expand a row for the licensed statement it rests on. We read the ADVERSE REACTIONS section of Ondansetron’s FDA label too, and the two lists don’t meaningfully overlap — which is why no Ondansetron column appears here.

Special populations

Carrageenan in Pregnancy & Breastfeeding

Pregnancy And Lactation Likely Safe

When used in food amounts. There is insufficient reliable information available about the safety of using larger amounts; avoid using.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center

From our Q&A

Questions About Carrageenan or Ondansetron

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Carrageenan or Ondansetron, 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 Ondansetron

This page covers Carrageenan only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Ondansetron page lists 195 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Grapefruit (major), Lithium (major), St. John's Wort (major) and 1,3-dmaa (moderate).

By severity: 4 major · 145 moderate · 46 minor.

From our pharmacist’s overview on the Ondansetron page

“Ondansetron (Zofran) often stands between you and relentless nausea from chemotherapy or surgery, so read this page carefully. Four of the 195 ingredients rate major.”

Reviewed by 2 · Jul 18, 2026

Open the Ondansetron interaction page

One more smart check

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

We hold 31 real supplement products containing Carrageenan, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Carrageenan. Even though Carrageenan itself has no known interaction with Ondansetron, 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 Carrageenan and Ondansetron 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 Carrageenan
Top half

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

29 days ago today
Medication Ondansetron
Steady interest

#2,073 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 Carrageenan reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Carrageenan and Ondansetron 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 Carrageenan

What is Carrageenan?

  • Food thickener and stabilizer
  • Digestive complaints (traditional use)
  • Cough and sore throat (traditional use)
  • Laxative or bowel-related uses
  • Antiviral (laboratory interest)

Carrageenan is a fiber-like substance taken from red seaweed and is mostly used as a thickener and gelling agent in foods. There is little solid human evidence supporting it as a health supplement, and some forms (especially degraded carrageenan) have raised digestive and inflammation concerns, so it should not be relied on to treat any condition.

Extracted polysaccharide from red seaweed (Rhodophyceae) · Food additive (thickener/gel), capsules, and occasional supplement blends

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

Carrageenan: dosing

There is no established standard supplement dose of carrageenan. In foods, it is used in small amounts purely as a texture ingredient, not as a measured health dose.If you choose to use a product that contains carrageenan, follow the directions on the label and do not exceed them.

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

Read the full Carrageenan monograph & all interactions
Medication

About Ondansetron

What Is Ondansetron Used For?

Brand name: Zofran

Ondansetron is used to prevent nausea and vomiting in several situations. Oral forms (tablets, orally disintegrating tablets, and oral solution) are approved to prevent nausea and vomiting from highly or moderately emetogenic (nausea-causing) cancer chemotherapy, from radiation therapy to the abdomen or whole body, and from surgery.

Ondansetron injection (given intravenously or intramuscularly in a clinical setting) is approved to prevent nausea and vomiting from emetogenic cancer chemotherapy — including high-dose cisplatin — in adults and children as young as 6 months old, as well as to prevent postoperative nausea and vomiting.

Most-Reported Side Effects for Ondansetron

From FAERS, the FDA’s public side-effect reporting system (121,840 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Nausea 14,459 reports
Fatigue 10,275 reports
Diarrhea 9,488 reports
Vomiting 8,777 reports
Dyspnea 5,971 reports
See full Ondansetron drug information
Keep checking

Other Drugs & Carrageenan

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

0Major
122Moderate
0Minor
2,707No known interaction
122 Moderate 2,707 No interaction
Moderate

122 interactions

Showing 60 of 122 moderate interactions — see all 122 on the Carrageenan page.

No interaction 2,707 drugs checked — show the list

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

Showing the 60 most looked-up of 2,707 medications checked with no known interaction — see the full Carrageenan list.

See the full Carrageenan interactions page
See every supplement checked against Ondansetron, ranked by severity
Evidence & sources

Carrageenan References

The 6 references that drive our Carrageenan 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. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Food, Drugs and Cosmetics. 2nd ed. New York, NY: John Wiley & Sons, 1996.
  2. Fetrow CW, Avila JR. Professional's Handbook of Complementary & Alternative Medicines. 1st ed. Springhouse, PA: Springhouse Corp., 1999.
  3. Coggins, C., Blanchard, K., Alvarez, F., Brache, V., Weisberg, E., Kilmarx, P. H., Lacarra, M., Massai, R., Mishell, D., Jr., Salvatierra, A., Witwatwongwana, P., Elias, C., and Ellertson, C. Preliminary safety and acceptability of a carrageenan gel for
  4. Tobacman, J. K., Wallace, R. B., and Zimmerman, M. B. Consumption of carrageenan and other water-soluble polymers used as food additives and incidence of mammary carcinoma. Med.Hypotheses 2001;56(5):589-598. PubMed
  5. Elias, C. J., Coggins, C., Alvarez, F., Brache, V., Fraser, I. S., Lacarra, M., Lahteenmaki, P., Massai, R., Mishell, D. R., Jr., Phillips, D. M., and Salvatierra, A. M. Colposcopic evaluation of a vaginal gel formulation of iota-carrageenan. Contracepti PubMed
  6. Laurie C, El-Zein M, Tota JE, et al. Efficacy of a carrageenan gel in preventing anal human papillomavirus (HPV) infection: interim analysis of the Lubricant Investigation in Men to Inhibit Transmission of HPV Infection (LIMIT-HPV) randomised controlled t

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 Carrageenan and Ondansetron Together: Common Questions

Is it safe to take Carrageenan with Ondansetron?
We do not list a known interaction between Carrageenan and Ondansetron. 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.
How was the Carrageenan and Ondansetron combination checked?
Interactions in our licensed database are recorded against drug classes. Ondansetron is filed under 7 classifications, and Carrageenan has documented interactions with 1 drug class — none of Ondansetron'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 Carrageenan interact with any other medications?
Yes. Carrageenan has 122 documented drug interactions in our database — Ondansetron 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 Ondansetron interact with any supplements?
Yes. Ondansetron has documented interactions with 195 supplements in our database — Carrageenan is not one of them. The Ondansetron 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

Carrageenan monograph Uses, safety profile, and every drug interaction in one place Ondansetron drug information The full plain-English guide to this medication Ondansetron supplement interactions Every supplement checked against Ondansetron, 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 6 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Ondansetron and Carrageenan?

Our pharmacists answer your medication & supplement questions — free.

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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.