Drug & supplement interaction

Fish Oil + Heparin

Heparin brand name: Heparin.

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

Fish Oil has a minor interaction with Heparin. Fish oil may have antiplatelet effects and may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.

Read the full interaction report
SeverityMinor
LikelihoodUnlikely
EvidenceB
What do Severity, Likelihood & Evidence mean?
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Interaction report

Fish Oil and Heparin

Here is the interaction we found between these two, with the evidence behind it.

Minor

ANTICOAGULANT/ANTIPLATELET DRUGS

Why this applies to Heparin

Heparin falls under ANTICOAGULANT/ANTIPLATELET DRUGS — the group Fish Oil interacts with.

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 simple version. Heparin is a strong blood thinner that keeps clots from forming, and fish oil can act a little like a mild blood thinner of its own by making your platelets slightly less sticky. Put them together and, in theory, you could be a touch more prone to bleeding. Think easier bruising, nosebleeds, bleeding gums, or a small cut that takes longer to stop.

The good news is that the evidence here is weak and the worry is mostly theoretical. Solid studies show fish oil at normal doses (around 1 to 4 grams a day) usually doesn't meaningfully change bleeding or clotting numbers. Since heparin is closely monitored anyway, this is a minor concern. Still, let your doctor or pharmacist know you take fish oil so they keep an eye on things.

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 207 moderate, 119 minor known drug interactions in our database — the Heparin one above is one of them. If you take anything else, check it against the full list below.

Moderate 207 Minor 119 No known interaction 2,504 (incl. Heparin)
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 Heparin

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 Heparin, 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 Heparin

This page covers Fish Oil only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Heparin page lists 202 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Danshen (major), Piracetam (major), Aconite (moderate), Allspice (moderate) and Aloe (moderate).

By severity: 2 major · 183 moderate · 17 minor.

From our pharmacist’s overview on the Heparin page

“Heparin exists to keep clots from forming, and all 202 supplements on this list touch that same clotting machinery, so treat these pairings with real care. Nearly all lean the same way, adding antiplatelet or anticoagulant activity that can push a therapeutic dose toward bruising and bleeding.”

Reviewed by 2 · Jul 18, 2026

Open the Heparin 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 Heparin 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 Heparin 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%

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

29 days ago today
Medication Heparin
Top half

#796 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 Heparin Injection

What Is Heparin Injection Used For?

Brand name: Heparin

Heparin Sodium Injection is used to prevent and treat blood clots in the veins and lungs (venous thrombosis and pulmonary embolism), including after major abdominal or chest surgery. It is also used for atrial fibrillation (an irregular heart rhythm) when there is a risk of clots breaking off and traveling through the body, and to treat disseminated intravascular coagulation (DIC), a serious condition where the blood clots abnormally throughout the body.

It is also used to prevent clotting during heart and artery surgery, to treat peripheral arterial embolism (a clot blocking blood flow to the limbs), and as an anticoagulant during blood transfusions, heart-lung bypass (extracorporeal circulation), and dialysis procedures.

See full Heparin Injection 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
207Moderate
119Minor
2,503No known interaction
207 Moderate 119 Minor 2,503 No interaction
Moderate

207 interactions

Showing 60 of 207 moderate interactions — see all 207 on the Fish Oil page.

Minor

119 interactions

Showing 60 of 119 minor interactions — see all 119 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 Heparin, 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 Heparin supplement interactions › Every supplement checked against Heparin, ranked by severity Heparin Injection 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 Heparin Together: Common Questions

Can you take Fish Oil with Heparin?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Fish Oil and Heparin interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

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

Still Have a Question About Heparin and Fish Oil?

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.