Drug & supplement interaction

Krill Oil + 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 Krill Oil 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. Additionally, although there is no interaction, 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

Krill Oil 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 Krill Oil 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.

Krill Oil safety at a glance

Krill Oil overall Use caution Generally well tolerated, but avoid if you have a shellfish allergy and use caution if you have a bleeding disorder.
Pregnancy Use caution Not enough reliable safety data; talk to your doctor before using during pregnancy.
Breastfeeding Use caution Not enough reliable safety data; talk to your doctor before using while breastfeeding.

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

Still wondering about combining Ondansetron and Krill Oil? 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. Krill Oil has documented interactions with 2 drug classes — the most serious being anticoagulant/antiplatelet drugs (moderate) and antidiabetes 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

Krill Oil Does Interact With Other Medications

Krill Oil has 208 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 208 No known interaction 2,622 (incl. Ondansetron)
Taking anything else?

Check Another of Your Medications Against Krill Oil

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

What to actually watch for

No Interaction Found — But Data Suggests Krill Oil and Ondansetron May Share a Side Effect

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. One of them is worth acting on rather than waiting out — marked below.

  • Raised blood pressure Worth acting on Additional detail

    Krill Oil

    “Orally, krill oil may cause hypertension, but this effect has only been observed for one patient in one clinical trial.”

    Krill Oil · Natural Medicines adverse-effect record, reported in hypertension.

    1 source cited
    1. 91600. Berge K, Musa-Veloso K, Harwood M, Hoem N, Burri L. Krill oil supplementation lowers serum triglycerides without increasing low-density lipoprotein cholesterol in adults with borderline high or high triglyceride levels. Nutr Res 2014;34(2):126-33. PubMed

    Ondansetron

    Listed in the ADVERSE REACTIONS section of the FDA label for Ondansetron. Read the label on DailyMed ›

Reported for Krill Oil but not commonly for Ondansetron: stomach upset, reduced appetite, sore throat and bloating or gas.

Effects for Ondansetron come from the ADVERSE REACTIONS section of its FDA label; effects for Krill Oil come from the Natural Medicines adverse-effect record, quoted above. Where a percentage is shown, it is the share of 121,840 voluntary FDA FAERS reports for Ondansetron that mention that effect — a reporting proportion, not an incidence rate and not evidence the drug caused it. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Overlapping uses

What Ondansetron Is Prescribed For, and What Krill Oil Has Been Studied For

These two come up together because they touch the same health topic — not because they do the same job. Ondansetron is a prescription medicine with approved uses on its FDA label. Krill Oil is a supplement: what follows is what researchers have looked at it for, and how strong that evidence is.

Ondansetron is prescribed for: 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.

Krill Oil has been studied for:

  • Cancer studied, not established Krill Oil has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows

    Krill Oil for cancer

    Although there has been interest in using oral krill oil for cancer prevention, there is insufficient reliable information about the clinical effects of krill oil for this condition.

Effectiveness ratings and the research summaries above are the verbatim record from the Natural Medicines database, which grades evidence from “Effective” down to “Insufficient Reliable Evidence To Rate”. A rating below the top of that scale means researchers have looked at it — not that it works, and never that it can stand in for a prescribed medicine. Do not stop or replace Ondansetron on your own; if you are taking Krill Oil for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

From our Q&A

Questions About Krill Oil 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 Krill Oil 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 Krill Oil 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 Krill Oil as Part of a Dietary Supplement Product? Check It for Interactions

We hold 605 real supplement products containing Krill Oil, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Krill Oil. Even though Krill Oil 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 Krill Oil 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 Krill Oil
Top 25%

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

29 days ago today
Medication Ondansetron
Steady interest

#1,687 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 Krill Oil reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Krill Oil 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 Krill Oil

What is Krill Oil?

Krill Oil
  • Heart and cholesterol support
  • High triglycerides
  • Joint pain and inflammation
  • Brain and eye health
  • PMS symptoms
  • General omega-3 supplementation

Krill oil is a source of omega-3 fatty acids (EPA and DHA) bound to phospholipids, which may help absorption. It is most studied for lowering triglycerides and supporting heart health, but the evidence for many other uses is limited. It is generally well tolerated, but people with shellfish allergy should avoid it, and anyone pregnant, breastfeeding, or on blood thinners should check with a pharmacist or doctor first.

Euphausia superba · Euphausiidae · Oil extracted from the whole krill · Softgel capsules, liquid

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

Krill Oil: dosing

There is no single official or standardized dose of krill oil. Products vary in how much EPA and DHA they provide per capsule, so two products may not be equal even at the same number of capsules.The best approach is to follow the directions on the product label and to choose a reputable brand.

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

Read the full Krill Oil 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 & Krill Oil

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

0Major
208Moderate
0Minor
2,621No known interaction
208 Moderate 2,621 No interaction
Moderate

208 interactions

Showing 60 of 208 moderate interactions — see all 208 on the Krill Oil page.

No interaction 2,621 drugs checked — show the list

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

Showing the 60 most looked-up of 2,621 medications checked with no known interaction — see the full Krill Oil list.

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

Krill Oil References

The 13 references that drive our Krill Oil 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. Leaf A. On the reanalysis of the GISSI-Prevenzione. Circulation 2002;105:1874-5. PubMed
  2. Connor WE. n-3 Fatty acids from fish and fish oil: panacea or nostrum? Am J Clin Nutr 2001;74;415-6. PubMed
  3. Calder PC. N-3 polyunsaturated fatty acids, inflammation and immunity: pouring oil on troubled waters or another fishy tale? Nutr Res 2001;21:309-41. DOI
  4. Bunea R, El Farrah K, Deutsch L. Evaluation of the effects of Neptune Krill Oil on the clinical course of hyperlipidemia. Altern Med Rev 2004;9:420-8.
  5. Sampalis F, Bunea R, Pelland MF, et al. Evaluation of the effects of Neptune Krill Oil on the management of premenstrual syndrome and dysmenorrhea. Altern Med Rev 2003;8:171-9.
  6. Harris WS, Miller M, Tighe AP, et al. Omega-3 fatty acids and coronary heart disease risk: clinical and mechanistic perspectives. Atherosclerosis 2008;197:12-24. PubMed
  7. Tandy S, Chung RW, Wat E, et al. Dietary krill oil supplementation reduces hepatic steatosis, glycemia, and hypercholesterolemia in high-fat-fed mice. J Agric Food Chem 10-14-2009;57:9339-45. PubMed
  8. Maki, K. C., Reeves, M. S., Farmer, M., Griinari, M., Berge, K., Vik, H., Hubacher, R., and Rains, T. M. Krill oil supplementation increases plasma concentrations of eicosapentaenoic and docosahexaenoic acids in overweight and obese men and women. Nutr.R PubMed
  9. Albert BB, Derraik JG, Brennan CM, et al. Supplementation with a blend of krill and salmon oil is associated with increased metabolic risk in overweight men. Am J Clin Nutr 2015;102(1):49-57.
  10. Berge K, Musa-Veloso K, Harwood M, Hoem N, Burri L. Krill oil supplementation lowers serum triglycerides without increasing low-density lipoprotein cholesterol in adults with borderline high or high triglyceride levels. Nutr Res 2014;34(2):126-33. PubMed
  11. Lobraico JM, DiLello LC, Butler AD, Cordisco ME, Petrini JR, Ahmadi R. Effects of krill oil on endothelial function and other cardiovascular risk factors in participants with type 2 diabetes, a randomized controlled trial. BMJ Open Diabetes Res Care. 2015 PubMed
  12. van der Wurff ISM, von Schacky C, Bergeland T, Zeegers MP, Kirschner PA, de Groot RHM. Krill oil supplementation's effect on school grades in typically developing adolescents. Prostaglandins Leukot Essent Fatty Acids 2023;191:102553. PubMed
  13. van der Wurff ISM, von Schacky C, Bergeland T, et al. Effect of 1 year krill oil supplementation on cognitive achievement of Dutch adolescents: A double-blind randomized controlled trial. Nutrients. 2019;11(6):1230. 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 Krill Oil and Ondansetron Together: Common Questions

Is it safe to take Krill Oil with Ondansetron?
We do not list a known interaction between Krill Oil 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.
Do Krill Oil and Ondansetron have any of the same side effects?
Yes — our sources link each of them separately to one 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.
Are Krill Oil and Ondansetron used for the same thing?
They overlap in purpose, which usually means the real question is whether you need both rather than whether they are safe together. This page lists the shared uses and how strong the evidence is for Krill Oil in each. That is a conversation for your prescriber, especially if Ondansetron is being adjusted to a target.
How was the Krill Oil and Ondansetron combination checked?
Interactions in our licensed database are recorded against drug classes. Ondansetron is filed under 7 classifications, and Krill Oil has documented interactions with 2 drug classes — 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 Krill Oil interact with any other medications?
Yes. Krill Oil has 208 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 — Krill Oil 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

Krill Oil 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 13 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Ondansetron and Krill Oil?

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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.