Drug & supplement interaction

Fish Oil + Treprostinil

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Treprostinil falls into 2 drug categories that Fish Oil can interact with; the most serious is rated moderate. Theoretically, taking fish oil with antihypertensive drugs might increase the risk of hypotension.

Read the full interaction report
SeverityModerate
LikelihoodProbable
Interactions2
EvidenceB
What do Severity, Likelihood & Evidence mean?
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Interaction report

Fish Oil and Treprostinil

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Fish Oil interacts with whole categories of medication. Treprostinil falls into 2 of those categories, so it can interact with Fish Oil in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

ANTIHYPERTENSIVE DRUGS

1 of 2

Why this applies to Treprostinil

Treprostinil falls under ANTIHYPERTENSIVE DRUGS — the group Fish Oil interacts with.

Theoretically, taking fish oil with antihypertensive drugs might increase the risk of hypotension.
Clinical evidence indicates that fish oils can modestly lower blood pressure and might have additive effects in patients treated with antihypertensives.
Severity Moderate Likelihood Probable Evidence B

Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the simple version: treprostinil (Orenitram) already lowers blood pressure by relaxing and widening your blood vessels, which is how it helps with pulmonary arterial hypertension. Fish oil, taken in concentrated supplement doses, can nudge blood pressure down a little on its own. Put them together and those effects can add up.

What that might feel like is more lightheadedness, dizziness, headache, flushing, or feeling faint when you stand up. Good news: this isn't a dramatic or dangerous clash, and the evidence behind it is fairly modest. A serving of fish at dinner is very unlikely to matter. Still, since treprostinil dosing is carefully managed, I'd check with your pharmacist or doctor before adding a fish oil supplement so they can keep an eye on your numbers.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Prisco D, Paniccia R, Bandinelli B, et al. Effect of medium-term supplementation with a moderate dose of n-3 polyunsaturated fatty acids on blood pressure in mild hypertensive patients. Thromb Res 1998;1:105-12.
  2. Toft I, Bonaa KH, Ingebretsen OC, et al. Effects of n-3 polyunsaturated fatty acids on glucose homeostasis and blood pressure in essential hypertension. A randomized, controlled trial. Ann Intern Med 1995;123:911-8.
  3. Sacks FM, Hebert P, Appel LJ, et al. Short report: the effect of fish oil on blood pressure and high-density lipoprotein-cholesterol levels in phase I of the trials of hypertension prevention. J Hypertens 1994;12:209-13.
  4. Vandongen R, Mori TA, Burke V, et al. Effects on blood pressure of omega 3 fats in subjects at increased risk of cardiovascular disease. Hypertension 1993;22:371-9. PubMed
  5. Bonaa, K. H., Bjerve, K. S., Straume, B., Gram, I. T., and Thelle, D. Effect of eicosapentaenoic and docosahexaenoic acids on blood pressure in hypertension. A population-based intervention trial from the Tromso study. N Engl J Med 3-22-1990;322(12):795- DOI
  6. Singer, P., Melzer, S., Goschel, M., and Augustin, S. Fish oil amplifies the effect of propranolol in mild essential hypertension. Hypertension 1990;16(6):682-691. PubMed
  7. Knapp, H. R. and FitzGerald, G. A. The antihypertensive effects of fish oil. A controlled study of polyunsaturated fatty acid supplements in essential hypertension. N Engl J Med 4-20-1989;320(16):1037-1043. PubMed
  8. Lungershausen, Y. K., Abbey, M., Nestel, P. J., and Howe, P. R. Reduction of blood pressure and plasma triglycerides by omega-3 fatty acids in treated hypertensives. J Hypertens. 1994;12(9):1041-1045. DOI
  9. Appel, L. J., Miller, E. R., III, Seidler, A. J., and Whelton, P. K. Does supplementation of diet with 'fish oil' reduce blood pressure? A meta-analysis of controlled clinical trials. Arch Intern Med 6-28-1993;153(12):1429-1438. DOI
  10. Morris, M. C., Sacks, F., and Rosner, B. Does fish oil lower blood pressure? A meta-analysis of controlled trials. Circulation 1993;88(2):523-533. PubMed
  11. Morris, M. C., Taylor, J. O., Stampfer, M. J., Rosner, B., and Sacks, F. M. The effect of fish oil on blood pressure in mild hypertensive subjects: a randomized crossover trial. Am J Clin Nutr 1993;57(1):59-64. PubMed
Minor

ANTICOAGULANT/ANTIPLATELET DRUGS

2 of 2

Treprostinil also falls under ANTICOAGULANT/ANTIPLATELET DRUGS.

Fish oil may have antiplatelet effects and may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs. However, evidence is conflicting.
While fish oil may not be a potent inhibitor of platelet function, high doses of fish oil might have antiplatelet effects. Theoretically, concomitant use of fish oil with anticoagulant or antiplatelet drugs may increase the risk of bleeding. However, the most rigorous research shows that short-term doses of fish oil 10 grams daily or long-term doses of 1.5 grams daily for up to 52 weeks does not increase the risk of bleeding or affect coagulation parameters in chronically ill and vulnerable patients. Other controlled research shows that fish oil does not affect platelet function or increase the risk of bleeding. Some research even suggests that perioperative fish oil use decreases bleeding risk. Some research suggests fish oil does not have additive antiplatelet effects when combined with aspirin, but other clinical evidence suggests that adding fish oil to low-dose aspirin treatment increases antiplatelet effects in patients who are aspirin-resistant. Also, some clinical research seems to show that fish oil has additive antiplatelet effects when used with aspirin and clopidogrel compared to aspirin and clopidogrel alone.
Severity Minor Likelihood Unlikely Evidence B

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the thing about combining fish oil with treprostinil (Orenitram): treprostinil itself is a prostacyclin medicine used for pulmonary arterial hypertension, and one of its built-in effects is that it relaxes blood vessels and can also mildly reduce how well platelets stick together. Fish oil, especially at higher concentrated doses, may add a little to that platelet-thinning effect. So the small concern here is a slightly higher chance of bruising or bleeding, like nosebleeds or gums bleeding when you brush.

That said, this is rated minor and unlikely, and the better-quality studies haven't shown meaningful bleeding from fish oil at typical doses. Eating fish is not a worry. If you take a high-dose supplement, just mention it to your pharmacist or doctor before starting or stopping anything.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  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. Svaneborg N, Kristensen SD, Hansen LM, et al. The acute and short-time effect of supplementation with the combination of n-3 fatty acids and acetylsalicylic acid on platelet function and plasma lipids. Thromb Res 2002;105:311-6. PubMed
  5. Kwak SM, Myung SK, Lee YJ, Seo HG. Efficacy of omega-3 fatty acid supplements (eicosapentaenoic acid and docosahexaenoic acid) in the secondary prevention of cardiovascular disease: a meta-analysis of randomized, double-blind, placebo-controlled trials. A PubMed
  6. Armaganijan L, Lopes RD, Healey JS, et al. Do omega-3 fatty acids prevent atrial fibrillation after open heart surgery? A meta-analysis of randomized controlled trials. Clinics (Sao Paulo) 2011;66:1923-8.
  7. von Houwelingen R, Nordøy A, van der Beek E, et al. Effect of a moderate fish intake on blood pressure, bleeding time, hematology, and clinical chemistry in healthy males. Am J Clin Nutr. 1987 Sep;46(3):424-36. PubMed
  8. Goodnight SH Jr, Harris WS, Connor WE. The effects of dietary omega 3 fatty acids on platelet composition and function in man: a prospective, controlled study. Blood. 1981 Nov;58(5):880-5. DOI
  9. Gajos G1, Rostoff P, Undas A, et al. Effects of polyunsaturated omega-3 fatty acids on responsiveness to dual antiplatelet therapy in patients undergoing percutaneous coronary intervention: the OMEGA-PCI (OMEGA-3 fatty acids after pci to modify responsive
  10. Lev EI, Solodky A, Harel N, et al. Treatment of aspirin-resistant patients with omega-3 fatty acids versus aspirin dose escalation. J Am Coll Cardiol. 2010 Jan 12;55(2):114-21. DOI
  11. Salvig, J. D. and Lamont, R. F. Evidence regarding an effect of marine n-3 fatty acids on preterm birth: a systematic review and meta-analysis. Acta Obstet.Gynecol.Scand. 2011;90(8):825-838. PubMed
  12. Zucker, M. L., Bilyeu, D. S., Helmkamp, G. M., Harris, W. S., and Dujovne, C. A. Effects of dietary fish oil on platelet function and plasma lipids in hyperlipoproteinemic and normal subjects. Atherosclerosis 1988;73(1):13-22. PubMed
  13. Demke, D. M., Peters, G. R., Linet, O. I., Metzler, C. M., and Klott, K. A. Effects of a fish oil concentrate in patients with hypercholesterolemia. Atherosclerosis 1988;70(1-2):73-80. PubMed
  14. Mozaffarian D, Wu JH, de Oliveira Otto MC, Sandesara CM, Metcalf RG, Latini R, Libby P, Lombardi F, O'Gara PT, Page RL, Silletta MG, Tavazzi L, Marchioli R. Fish oil and post-operative atrial fibrillation: a meta-analysis of randomized controlled trials. PubMed
  15. Xin W, Wei W, Lin Z, Zhang X, Yang H, Zhang T, Li B, Mi S. Fish oil and atrial fibrillation after cardiac surgery: a meta-analysis of randomized controlled trials. PLoS One 2013;8(9):e72913. PubMed
  16. Jeansen S, Witkamp RF, Garthoff JA, van Helvoort A, Calder PC. Fish oil LC-PUFAs do not affect blood coagulation parameters and bleeding manifestations: Analysis of 8 clinical studies with selected patient groups on omega-3-enriched medical nutrition. Cli PubMed
  17. Fradet S, Pelletier JF, Singbo N, et al. Effects of omega-3 fatty acids supplementation on perioperative blood loss and complications after radical prostatectomy. Clin Nutr ESPEN 2022;47:221-226. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Fish Oil Also Interacts With Other Medications

Fish Oil has 206 moderate, 120 minor known drug interactions in our database — the Treprostinil one above is among them. If you take anything else, check it against the full list below.

Moderate 206 Minor 120 No known interaction 2,504 (incl. Treprostinil)
Taking anything else?

Check Another of Your Medications Against Fish Oil

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

From our Q&A

Questions About Fish Oil or Treprostinil

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

This page covers Fish Oil only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Treprostinil page lists 291 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), American Mistletoe (major), Danshen (major) and Piracetam (major).

By severity: 6 major · 258 moderate · 27 minor.

Open the Treprostinil interaction page

One more smart check

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

We hold 4,777 real supplement products containing Fish Oil, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Fish Oil. Your product may carry other ingredients that interact with Treprostinil too, on top of Fish Oil — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Fish Oil and Treprostinil 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 Fish Oil
Top 5%

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

29 days ago today
Medication Treprostinil
Steady interest

#2,470 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.

Supplement

About Fish Oil

What is Fish Oil?

Fish Oil
  • High triglycerides
  • Heart health
  • Joint pain and inflammation
  • Brain and eye health
  • Dry eyes

Fish oil provides omega-3 fatty acids (EPA and DHA) that are best known for lowering high triglyceride levels. The evidence for other heart and health benefits is mixed, and it is generally well tolerated. Talk with your pharmacist or doctor before starting it, especially if you take blood thinners or have a fish allergy.

Read the full Fish Oil monograph & all interactions
Medication

About Treprostinil

What Is Treprostinil Used For?

Treprostinil treats pulmonary arterial hypertension (PAH; WHO Group 1) — high blood pressure in the arteries of the lungs. Depending on the product and route, it is used to improve exercise ability, delay disease progression, or reduce symptoms tied to physical activity. Remodulin and treprostinil injection products are also indicated for patients who need to transition away from another PAH medicine called epoprostenol.

Tyvaso, Tyvaso DPI, and Yutrepia (inhaled forms) are additionally approved to treat pulmonary hypertension associated with interstitial lung disease (PH-ILD; WHO Group 3) — lung-pressure problems caused by scarring or inflammation in the lung tissue itself. Orenitram (extended-release oral tablet) is specifically indicated to delay disease progression and improve exercise capacity in PAH.

See full Treprostinil drug information
Keep checking

Other Drugs & Fish Oil

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

0Major
206Moderate
120Minor
2,503No known interaction
206 Moderate 120 Minor 2,503 No interaction
Moderate

206 interactions

Showing 60 of 206 moderate interactions — see all 206 on the Fish Oil page.

Minor

120 interactions

Showing 60 of 120 minor interactions — see all 120 on the Fish Oil page.

No interaction 2,503 drugs checked — show the list

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

Showing the 60 most looked-up of 2,503 medications checked with no known interaction — see the full Fish Oil list.

See the full Fish Oil interactions page
See every supplement checked against Treprostinil, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Fish Oil monograph › Uses, safety, and every drug interaction in one place Treprostinil supplement interactions › Every supplement checked against Treprostinil, ranked by severity Treprostinil drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Fish Oil and Treprostinil Together: Common Questions

Can you take Fish Oil with Treprostinil?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Fish Oil and Treprostinil?
Treprostinil belongs to more than one drug category, and Fish Oil interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Fish Oil and Treprostinil interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

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

Still Have a Question About Treprostinil and Fish 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.