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SupplementScience

Fish Oil Side Effects & Safety

Reviewed by·PharmD, BCPS

This content is for informational purposes only and does not constitute medical advice. Consult your healthcare provider before starting any supplement. Full disclaimer

Safety Profile

Overall safety rating: Generally Safe

Potential Side Effects

  • Fishy burps and aftertaste — the most common complaint; reduced by enteric-coated capsules, triglyceride-form oil, refrigeration, or taking with meals
  • GI discomfort (nausea, diarrhea, bloating) — dose-dependent; start at 1g and increase gradually
  • Increased bleeding time — clinically insignificant at doses under 3g; relevant at high doses or with anticoagulants
  • Mild fishy body odor at high doses — uncommon but reported; may indicate oxidized (rancid) product
  • LDL cholesterol increase at very high doses — high-dose DHA (>2g) may modestly raise LDL in some individuals; EPA-only formulations avoid this

Drug & Supplement Interactions

  • Anticoagulants and antiplatelets (warfarin, aspirin, clopidogrel, heparin) — omega-3s have antiplatelet effects; additive bleeding risk at high doses
  • Antihypertensive medications — fish oil may lower blood pressure by 2-5 mmHg; monitor for additive hypotension
  • Orlistat — blocks fat absorption, reducing fish oil uptake; separate doses by 2+ hours
  • Statin medications — fish oil complements statins for triglyceride reduction (REDUCE-IT used fish oil + statin); no negative interaction
  • Cyclosporine — fish oil may alter cyclosporine levels; monitor in transplant patients

Maximum Dose

Do not exceed: 5g combined EPA+DHA/day (FDA considers up to 5g/day safe from supplements; prescription icosapent ethyl uses 4g/day under medical supervision)

Full Fish Oil Guide

References

  1. Bhatt DL, Steg PG, Miller M, Brinton EA, Jacobson TA, Ketchum SB, Doyle RT Jr, Juliano RA, Jiao L, Granowitz C, Tardif JC, Ballantyne CM (2019). Cardiovascular risk reduction with icosapent ethyl for hypertriglyceridemia. New England Journal of Medicine. DOI PubMed
  2. Abdelhamid AS, Brown TJ, Brainard JS, Biswas P, Thorpe GC, Moore HJ, Deane KH, Summerbell CD, Worthington HV, Song F, Hooper L (2020). Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database of Systematic Reviews. DOI PubMed
  3. Liao Y, Xie B, Zhang H, He Q, Guo L, Subramanieapillai M, Fan B, Lu C, McIntyre RS (2019). Efficacy of omega-3 PUFAs in depression: a meta-analysis. Translational Psychiatry. DOI PubMed
  4. Calder PC (2017). Omega-3 fatty acids and inflammatory processes: from molecules to man. Biochemical Society Transactions. DOI PubMed
  5. Goldberg RJ, Katz J (2007). A meta-analysis of the analgesic effects of omega-3 polyunsaturated fatty acid supplementation for inflammatory joint pain. Pain. DOI PubMed
  6. Dyerberg J, Madsen P, Moller JM, Aardestrup I, Schmidt EB (2010). Bioavailability of marine n-3 fatty acid formulations. Prostaglandins, Leukotrienes and Essential Fatty Acids. DOI PubMed
  7. Mocking RJ, Harmsen I, Assies J, Koeter MW, Ruhe HG, Schene AH (2016). Meta-analysis and meta-regression of omega-3 polyunsaturated fatty acid supplementation for major depressive disorder. Translational Psychiatry. DOI PubMed