Drug & supplement interaction

Flaxseed Oil + Phenytoin

Phenytoin brand names: Dilantin Kapseals, Dilantin, Di-Phen, Dilantin Infatabs, Phenytek, and others.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 13, 2026
The bottom line No known interaction

We found no known interaction between Flaxseed Oil and Phenytoin 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

Flaxseed Oil and Phenytoin

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 Phenytoin and Flaxseed 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.

Flaxseed Oil safety at a glance

Flaxseed Oil overall Use caution Generally well tolerated for most adults, but quality and dose vary by product.
Pregnancy Possibly Safe When used orally and appropriately for medicinal purposes, short-term. Although flaxseed oil has been used with apparent safety in clinical research in doses of... Read the full pregnancy detail
Breastfeeding Use caution Limited safety information during breastfeeding, so use only with medical advice.

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

Why No Interaction Is Listed for Phenytoin

Interactions in our licensed database are recorded against drug classes, not just single drug names. Phenytoin is filed under 14 classifications — including cytochrome p450 2c8 (cyp2c8) substrates, cytochrome p450 2c9 (cyp2c9) inducers, anticonvulsants. Flaxseed Oil has documented interactions with 3 drug classes — the most serious being anticoagulant/antiplatelet drugs (moderate), antihypertensive drugs (moderate) and ezetimibe (zetia) (moderate) — and none of Phenytoin’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 Oil Does Interact With Other Medications

Flaxseed Oil has 293 moderate known drug interactions in our database — Phenytoin isn’t one of them. If you take anything else, check it against the full list below.

Moderate 293 No known interaction 2,537 (incl. Phenytoin)
Taking anything else?

Check Another of Your Medications Against Flaxseed Oil

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

What to actually watch for

No Interaction Found — But Data Suggests Flaxseed Oil and Phenytoin 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 Oil

    “Orally, flaxseed oil is generally well tolerated. Topically, flaxseed oil seems to be well-tolerated.

    Most Common Adverse Effects:

    Topically: Itching, redness.

    Serious Adverse Effects (Rare):

    Orally: Severe allergic reactions such as anaphylaxis.”

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

    Phenytoin

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

Reported for Flaxseed Oil but not commonly for Phenytoin: diarrhea, stomach upset, dry mouth and itching.

Effects for Phenytoin come from the ADVERSE REACTIONS section of its FDA label; effects for Flaxseed Oil 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 Oil in Pregnancy & Breastfeeding

Pregnancy Possibly Safe

When used orally and appropriately for medicinal purposes, short-term. Although flaxseed oil has been used with apparent safety in clinical research in doses of 1-2 grams daily for up to 6 weeks, some population research has found that consuming flaxseed oil during the second and third trimesters of pregnancy is associated with a four-fold increased risk of premature birth.

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 Flaxseed Oil or Phenytoin

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 Oil or Phenytoin, 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 Phenytoin

This page covers Flaxseed Oil only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Phenytoin page lists 224 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,4-butanediol (major), Activated Charcoal (major), Beer (major), Gamma-hydroxybutyrate (ghb) (major) and Kava (major).

By severity: 9 major · 187 moderate · 28 minor.

From our pharmacist’s overview on the Phenytoin page

“Phenytoin (Dilantin) is a seizure medicine with a narrow therapeutic index, meaning small changes in its blood level can bring seizures back or tip over into toxicity, so I treat its supplement list with real seriousness. The biggest group, 78 ingredients, piles on sedation, and alcohol, kava, and GHB all rate major for exactly that re…”

Reviewed by 2 · Jul 18, 2026

Open the Phenytoin interaction page

One more smart check

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

We hold 1,329 real supplement products containing Flaxseed Oil, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Flaxseed Oil. Even though Flaxseed Oil itself has no known interaction with Phenytoin, 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 Oil and Phenytoin 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 Oil
Top 25%

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

29 days ago today
Medication Phenytoin
Steady interest

#1,757 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 Oil reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Flaxseed Oil and Phenytoin 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 Oil

What is Flaxseed Oil?

  • Source of omega-3 (ALA) fatty acids
  • Heart and cholesterol health
  • Dry skin and inflammation
  • Constipation
  • General wellness

Flaxseed oil is a plant-based source of the omega-3 fatty acid ALA, which the body can partly convert to the omega-3s found in fish oil. It may help support heart health and provide healthy fats, but evidence for most specific health claims is limited or mixed. It is generally well tolerated, but talk to your pharmacist or doctor before starting, especially if you are pregnant or have a bleeding risk.

Linum usitatissimum · Linaceae · Oil pressed from the seeds · Liquid oil, softgel capsules, salad oil

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

Flaxseed Oil: dosing

There is no official standardized dose of flaxseed oil for any health condition. Products vary widely in strength and in how much ALA they provide per serving.The safest approach is to follow the dose printed on the product label and not exceed it without medical advice. To keep the oil fresh, store it as directed (often refrigerated) and avoid using it for cooking at high heat.

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

Read the full Flaxseed Oil monograph & all interactions
Medication

About Phenytoin

What Is Phenytoin Used For?

Brand names: Dilantin Kapseals, Dilantin, Di-Phen, Dilantin Infatabs, Phenytek, Dilantin injection

Phenytoin is used to treat and prevent seizures. The specific types covered depend on the formulation. Oral extended-release capsules (including Phenytek), chewable tablets (including Dilantin Infatabs and Phenytoin Infatabs), and oral suspension (including Dilantin-125) are used for tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures; most oral forms also cover prevention and treatment of seizures occurring during or after neurosurgery. Chewable tablets and some capsule formulations also cover complex partial seizures.

Parenteral (injectable) phenytoin sodium is used for generalized tonic-clonic status epilepticus (a prolonged, life-threatening seizure emergency) and for prevention and treatment of seizures during neurosurgery. The IV form can also substitute short-term for oral phenytoin when a patient cannot take it by mouth.

Most-Reported Side Effects for Phenytoin

From FAERS, the FDA’s public side-effect reporting system (40,278 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Convulsion 3,522 reports
Seizure 3,095 reports
Toxicity to various agents 1,888 reports
Fall 1,604 reports
Dizziness 1,539 reports
See full Phenytoin drug information
Keep checking

Other Drugs & Flaxseed Oil

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

0Major
293Moderate
0Minor
2,536No known interaction
293 Moderate 2,536 No interaction
Moderate

293 interactions

Showing 60 of 293 moderate interactions — see all 293 on the Flaxseed Oil page.

No interaction 2,536 drugs checked — show the list

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

Showing the 60 most looked-up of 2,536 medications checked with no known interaction — see the full Flaxseed Oil list.

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

Flaxseed Oil References

The 21 references that drive our Flaxseed 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. 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. 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
  4. 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.
  5. 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
  6. Bloedon LT, Szapary PO. Flaxseed and cardiovascular risk. Nutr Rev 2004;62:18-27. DOI
  7. Laaksonen DE, Laukkanen JA, Niskanen L, et al. Serum linoleic and total polyunsaturated fatty acids in relation to prostate and other cancers: a population-based cohort study. Int J Cancer 2004;111:444-50.. PubMed
  8. Brouwer IA, Katan MB, Zock PL. Dietary alpha-linolenic acid is associated with reduced risk of fatal coronary heart disease, but increased prostate cancer risk: a meta-analysis. J Nutr 2004;134:919-22.
  9. Paschos GK, Magkos F, Panagiotakos DB, et al. Dietary supplementation with flaxseed oil lowers blood pressure in dyslipidaemic patients. Eur J Clin Nutr 2007;61:1201-6. PubMed
  10. Harper CR, Edwards MC, Jacobson TA. Flaxseed oil supplementation does not affect plasma lipoprotein concentration or particle size in human subjects. J Nutr 2006;136:2844-8. PubMed
  11. University of Montreal. Pregnant Women Consuming Flaxseed Oil Have High Risk Of Premature Birth.ScienceDaily, October 29, 2008. Available at: www.sciencedaily.com/releases/2008/10/081027140817.htm (Accessed May 14, 2009).
  12. Allman, M. A., Pena, M. M., and Pang, D. Supplementation with flaxseed oil versus sunflowerseed oil in healthy young men consuming a low fat diet: effects on platelet composition and function. Eur.J Clin.Nutr. 1995;49(3):169-178.
  13. Ursoniu S, Sahebkar A, Andrica F, Serban C, Banach M; Lipid and Blood Pressure Meta-analysis Collaboration Group. Effects of flaxseed supplements on blood pressure: a systematic review and meta-analysis of controlled clinical trial. Clin Nutr. 2016 Jun;3 PubMed
  14. Taghizadeh M, Jamilian M, Mazloomi M, Sanami M, Asemi Z. A randomized-controlled clinical trial investigating the effect of omega-3 fatty acids on vitamin E co-supplementation on markers of insulin metabolism and lipid profiles in gestational diabetes. J
  15. Blackwood DP, LaVallee RK, Al Busaidi A, Jassal DS, Pierce GN. A randomized trial of the effects of ezetimibe on the absorption of omega-3 fatty acids in cardiac disease patients: a pilot study. Clin Nutr ESPEN. 2015 Oct;10(5):e155-e159. 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 Oil and Phenytoin Together: Common Questions

Is it safe to take Flaxseed Oil with Phenytoin?
We do not list a known interaction between Flaxseed Oil and Phenytoin. 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 Oil and Phenytoin have any of the same side effects?
Yes — our sources link each of them separately to 2 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 was the Flaxseed Oil and Phenytoin combination checked?
Interactions in our licensed database are recorded against drug classes. Phenytoin is filed under 14 classifications, and Flaxseed Oil has documented interactions with 3 drug classes — none of Phenytoin'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 Oil interact with any other medications?
Yes. Flaxseed Oil has 293 documented drug interactions in our database — Phenytoin 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 Phenytoin interact with any supplements?
Yes. Phenytoin has documented interactions with 224 supplements in our database — Flaxseed Oil is not one of them. The Phenytoin 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

Flaxseed Oil monograph Uses, safety profile, and every drug interaction in one place Phenytoin drug information The full plain-English guide to this medication Phenytoin supplement interactions Every supplement checked against Phenytoin, 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 21 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Phenytoin and Flaxseed 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.