Drug & supplement interaction

Flaxseed + Granisetron

Granisetron brand names: Kytril, Sustol.

No Known Interaction
The bottom line No known interaction

We found no known interaction between Flaxseed and Granisetron 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 label for Granisetron states a food rule worth keeping to, 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

Flaxseed and Granisetron

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 Granisetron and Flaxseed 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.

Flaxseed safety at a glance

Flaxseed overall Use caution Generally safe as a food, but drink plenty of water and start with small amounts to reduce bloating and gas.
Pregnancy Possibly Unsafe When used orally. Flaxseed can have mild estrogenic effects. Theoretically, this might adversely affect pregnancy; however, there is no reliable clinical eviden... Read the full pregnancy detail
Breastfeeding Use caution Not enough reliable safety information exists for supplement doses while breastfeeding, so use caution.

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 Granisetron and Flaxseed? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Granisetron

Interactions in our licensed database are recorded against drug classes, not just single drug names. Granisetron is filed under 3 classifications — serotonergic drugs, serotonergic drugs, oral drugs. Flaxseed has documented interactions with 5 drug classes — the most serious being antibiotic drugs (moderate), anticoagulant/antiplatelet drugs (moderate) and antidiabetes drugs (moderate) — and none of Granisetron’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

Flaxseed Does Interact With Other Medications

Flaxseed has 597 moderate known drug interactions in our database — Granisetron isn’t one of them. If you take anything else, check it against the full list below.

Taking anything else?

Check Another of Your Medications Against Flaxseed

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

What to actually watch for

No Interaction Found — But Data Suggests Flaxseed and Granisetron 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. 2 of them are worth acting on rather than waiting out — marked below.

  • A severe allergic reaction / An allergic reaction Worth acting on Additional detail

    Flaxseed

    “Orally, flaxseed is usually well-tolerated.

    Most Common Adverse Effects:

    Orally: Bloating, diarrhea, gastrointestinal complaints.

    Serious Adverse Effects (Rare):

    Orally: Severe allergic reactions such as and anaphylaxis.”

    Flaxseed · Natural Medicines adverse-effect record, reported in diarrhea.

    Granisetron

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

  • Constipation / Stomach pain / Nausea Additional detail

    Flaxseed

    “Integrating flaxseed in the diet can cause digestive symptoms similar to other sources of dietary fiber including bloating, fullness, flatulence, abdominal pain, diarrhea, constipation, dyspepsia, and nausea. Higher doses are likely to cause more gastrointestinal side effects. Flaxseed can significantly increase the number of bowel movements and the risk for diarrhea.”

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

    6 sources cited
    1. 12910. Dodin S, Lemay A, Jacques H, et al. The effects of flaxseed dietary supplement on lipid profile, bone mineral density, and symptoms in menopausal women: a randomized, double-blind, wheat germ placebo-controlled clinical trial. J Clin Endocrinol Metab 2005 PubMed
    2. 16761. Demark-Wahnefried W, Polascik TJ, George SL, et al. Flaxseed supplementation (not dietary fat restriction) reduces prostate cancer proliferation rates in men presurgery. Cancer Epidemiol Biomarkers Prev 2008;17:3577-87. PubMed
    3. 16765. Thompson LU, Chen JM, Li T, et al. Dietary flaxseed alters tumor biological markers in postmenopausal breast cancer. Clin Cancer Res 2005;11:3828-35. PubMed
    4. 21198. Cockerell KM, Watkins AS, Reeves LB, et al. Effects of linseeds on the symptoms of irritable bowel syndrome: a pilot randomised controlled trial. J Hum Nutr Diet 2012;25:435-43. PubMed
    5. 21200. Colli MC, Bracht A, Soares AA, et al. Evaluation of the efficacy of flaxseed meal and flaxseed extract in reducing menopausal symptoms. J Med Food 2012;15:840-5. PubMed
    6. 22176. Simbalista RL, Sauerbronn AV, Aldrighi JM, Areas JA. Consumption of a flaxseed-rich food is not more effective than a placebo in alleviating the climacteric symptoms of postmenopausal women. J Nutr 2010;140:293-7. PubMed

    Granisetron

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

  • Diarrhea Additional detail

    Flaxseed

    Recorded for Flaxseed in the same Natural Medicines adverse-effect record shown under A severe allergic reaction / An allergic reaction above.

    Granisetron

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

Reported for Flaxseed but not commonly for Granisetron: a bowel blockage, bloating or gas and stomach upset.

Effects for Granisetron come from the ADVERSE REACTIONS section of its FDA label; effects for Flaxseed 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.

Special populations

Flaxseed in Pregnancy & Breastfeeding

Pregnancy Possibly Unsafe

When used orally. Flaxseed can have mild estrogenic effects. Theoretically, this might adversely affect pregnancy; however, there is no reliable clinical evidence about the effects of flaxseed on pregnancy outcomes.

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

How to take them

Some Granisetron Products Have a Food Rule — Flaxseed Should Not Break It

At least one FDA label for a product containing Granisetron says to take it on an empty stomach. Most supplements — Flaxseed included — are taken with a meal, so the easy mistake is swallowing both together at breakfast. Where that rule applies, keep Granisetron on its own and move Flaxseed to a meal later in the day.

This may not be true of your version. Food instructions belong to the product, not the ingredient: two Granisetron products can carry different directions, and extended-release forms often differ from immediate-release ones. The label we read is quoted below — check the directions on your own box or bottle, or ask your pharmacist, for how to take the exact product you were given.

Recommended Dosage ( 2.2 ): The recommended dosage in adults is 10 mg administered as a single subcutaneous injection at least 30 minutes before the start of emetogenic chemotherapy on Day 1.

From the Dosage and Administration section of the FDA label we read for Granisetron — where that label names a specific product, the instruction is that product's. Read the label on DailyMed ›

A food rule is not an interaction — it is about how much of the medicine you absorb. The directions that came with your own product, and your pharmacist, outrank anything on this page.

From our Q&A

Questions About Flaxseed or Granisetron

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

This page covers Flaxseed only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Granisetron page lists 38 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Lithium (major), 5-htp (moderate), Acetyl-l-carnitine (moderate) and Ayahuasca (moderate).

By severity: 2 major · 25 moderate · 11 minor.

From our pharmacist’s overview on the Granisetron page

“Granisetron (Kytril, Sustol) blocks serotonin signals to stop nausea from chemotherapy and surgery, and this is a list that warrants real caution before you add a supplement to it. Most of the entries raise serotonin themselves, and stacking them on a serotonin-acting drug can push toward serotonin syndrome, a dangerous overload of tha…”

Reviewed by 2 · Jul 18, 2026

Open the Granisetron interaction page

One more smart check

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

We hold 236 real supplement products containing Flaxseed, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Flaxseed. Even though Flaxseed itself has no known interaction with Granisetron, 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 Flaxseed and Granisetron 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 Flaxseed
Top half

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

29 days ago today
Medication Granisetron
Steady interest

#2,677 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 Flaxseed reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Flaxseed and Granisetron records this page draws on were last updated July 11, 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 Flaxseed

What is Flaxseed?

Flaxseed
  • Constipation and digestive health
  • High cholesterol
  • Heart health
  • Menopausal symptoms
  • Blood sugar support

Flaxseed is a nutritious food rich in fiber, omega-3 fats (ALA), and plant compounds called lignans. It is most reliably helpful for constipation and may modestly lower cholesterol, but evidence for many other uses is mixed or limited. It is generally safe as a food, but talk to your pharmacist or doctor before using it as a supplement, especially if you are pregnant or breastfeeding.

Linum usitatissimum · Linaceae · Seeds and seed oil · Whole seeds, ground meal, oil, capsules, powder

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

Flaxseed: dosing

There is no single official dose for flaxseed, and the right amount depends on why you are using it and the form you choose. Ground (milled) flaxseed is generally better absorbed than whole seeds, which can pass through undigested.The best approach is to follow the directions on the product label and start with a small amount, increasing slowly while drinking plenty of water.

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

Read the full Flaxseed monograph & all interactions
Medication

About Granisetron

What Is Granisetron Used For?

Brand names: Kytril, Sustol

Granisetron is used to prevent nausea and vomiting linked to emetogenic (nausea-causing) cancer chemotherapy — including high-dose cisplatin — and radiation therapy, including total body irradiation and fractionated abdominal radiation. Granisetron hydrochloride tablets and Granisol oral solution are approved for both the chemotherapy and radiation indications. Sancuso skin patch is approved for prevention of nausea and vomiting in adults receiving moderately and/or highly emetogenic chemotherapy regimens of up to 5 consecutive days.

Granisetron hydrochloride injection (intravenous) is also used to prevent and treat postoperative nausea and vomiting in adults. Sustol (subcutaneous injection) is used in combination with other anti-nausea medicines in adults specifically for the prevention of acute and delayed nausea and vomiting associated with moderately emetogenic chemotherapy or anthracycline and cyclophosphamide combination chemotherapy regimens.

See full Granisetron drug information
Keep checking

Other Drugs & Flaxseed

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

0Major
597Moderate
0Minor
2,232No known interaction
Moderate

597 interactions

Showing 60 of 597 moderate interactions — see all 597 on the Flaxseed page.

No interaction 2,232 drugs checked — show the list
Evidence & sources

Flaxseed References

The 37 references that drive our Flaxseed 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. Kolonel LN, Nomura AM, Cooney RV. Dietary fat and prostate cancer: current status. J Natl Cancer Inst 1999;91:414-28. PubMed
  2. Ramon JM, Bou R, Romea S, et al. Dietary fat intake and prostate cancer risk: a case-control study in Spain. Cancer Causes Control 2000;11:679-85. PubMed
  3. Thompson LU, Rickard SE, Cheung F, et al. Variability in anticancer lignan levels in flaxseed. Nutr Cancer 1997;27:26-30. PubMed
  4. Nordstrom DC, Honkanen VE, Nasu Y, et al. Alpha-linolenic acid in the treatment of rheumatoid arthritis. A double-blind, placebo-controlled and randomized study: flaxseed vs. safflower seed. Rheumatol Int 1995;14:231-4. PubMed
  5. Cunnane SC, Ganguli S, Menard C, et al. High alpha-linolenic acid flaxseed (Linum usitatissimum): some nutritional properties in humans. Br J Nutr 1993;69:443-53.
  6. Clark WF, Parbtani A, Huff MW, et al. Flaxseed: a potential treatment for lupus nephritis. Kidney Int 1995;48:475-80. PubMed
  7. Cunnane SC, Hamadeh MJ, Liede AC, et al. Nutritional attributes of traditional flaxseed in healthy young adults. Am J Clin Nutr 1995;61:62-8. PubMed
  8. De Stefani E, Deneo-Pellegrini H, Boffetta P, et al. Alpha-linolenic acid and risk of prostate cancer: a case-control study in Uruguay. Cancer Epidemiol Biomarkers Prev 2000;9:335-8.
  9. Giovannucci E, Rimm EB, Colditz GA, et al. A prospective study of dietary fat and risk of prostate cancer. J Natl Cancer Inst 1993;85:1571-9. PubMed
  10. Clark WF, Kortas C, Heidenheim P, et al. Flaxseed in lupus nephritis: a two-year nonplacebo-controlled crossover study. J Am Coll Nutr 2001;20:143-8. PubMed
  11. Serraino M, Thompson LU. The effect of flaxseed supplementation on early risk markers for mammary carcinogenesis. Cancer Lett 1991;60:135-42. PubMed
  12. Rickard SE, Yuan YV, Thompson LU. Plasma insulin-like growth factor I levels in rats are reduced by dietary supplementation of flaxseed or its lignan secoisolariciresinol diglycoside. Cancer Lett 2000;161:47-55. PubMed
  13. Mousavi Y, Adlercreutz H. Enterolactone and estradiol inhibit each other's proliferative effect on MCF-7 breast cancer cells in culture. J Steroid Biochem Mol Biol 1992;41:615-9.. PubMed
  14. Adlercreutz H, Fotsis T, Bannwart C, et al. Determination of urinary lignans and phytoestrogen metabolites, potential antiestrogens and anticarcinogens, in urine of women on various habitual diets. J Steroid Biochem 1986;25:791-7.. PubMed
  15. Rose DP. Dietary fiber and breast cancer. Nutr Cancer 1990;13:1-8.. 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 Flaxseed and Granisetron Together: Common Questions

Is it safe to take Flaxseed with Granisetron?
We do not list a known interaction between Flaxseed and Granisetron. 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 Flaxseed and Granisetron have any of the same side effects?
Yes — our sources link each of them separately to 6 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.
Should I take Flaxseed and Granisetron at the same time of day?
At least one FDA label for a product containing Granisetron says to take it on an empty stomach, and supplements are usually taken with a meal — so taking them together at breakfast is the easy mistake. Where that applies, keep Granisetron on its own and move Flaxseed to a meal later in the day. Food instructions belong to the product rather than the ingredient, so check the directions on your own box. This is about absorption, not an interaction.
How was the Flaxseed and Granisetron combination checked?
Interactions in our licensed database are recorded against drug classes. Granisetron is filed under 3 classifications, and Flaxseed has documented interactions with 5 drug classes — none of Granisetron'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 Flaxseed interact with any other medications?
Yes. Flaxseed has 597 documented drug interactions in our database — Granisetron 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 Granisetron interact with any supplements?
Yes. Granisetron has documented interactions with 38 supplements in our database — Flaxseed is not one of them. The Granisetron interaction page linked on this page lists every one, ranked by severity.

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

Still Have a Question About Granisetron and Flaxseed?

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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.