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Types of Fish Oil: Forms & Bioavailability

Evidence:Strong
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This content is for informational purposes only and does not constitute medical advice. Statements about dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease. Individual results may vary — consult your healthcare provider before starting any supplement. Full disclaimer

Forms Comparison

FormBioavailabilityBest For
Triglyceride Form (rTG)HighOptimal absorption — re-esterified triglyceride form is 70% better absorbed than ethyl esters; the gold standard for consumer fish oil supplements
Ethyl Ester Form (EE)ModerateConcentrated EPA/DHA per capsule — allows higher potency but lower bioavailability; must be taken with a high-fat meal; form used in most clinical trials including REDUCE-IT
Liquid Fish OilHighHigh-dose supplementation without swallowing multiple capsules — flavored versions mask taste; allows precise dose titration
Enteric-Coated SoftgelsHighEliminating fishy burps — coating prevents capsule dissolution in the stomach, releasing omega-3s in the small intestine instead; slightly delayed absorption

Triglyceride Form (rTG)

Bioavailability: High. Best for: Optimal absorption — re-esterified triglyceride form is 70% better absorbed than ethyl esters; the gold standard for consumer fish oil supplements.

Ethyl Ester Form (EE)

Bioavailability: Moderate. Best for: Concentrated EPA/DHA per capsule — allows higher potency but lower bioavailability; must be taken with a high-fat meal; form used in most clinical trials including REDUCE-IT.

Liquid Fish Oil

Bioavailability: High. Best for: High-dose supplementation without swallowing multiple capsules — flavored versions mask taste; allows precise dose titration.

Enteric-Coated Softgels

Bioavailability: High. Best for: Eliminating fishy burps — coating prevents capsule dissolution in the stomach, releasing omega-3s in the small intestine instead; slightly delayed absorption.

Find the best Fish Oil for your needs
Ranked by form, bioavailability, and value
Full Fish Oil Guide

References

  1. RCTBhatt 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. Meta-analysisAbdelhamid 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. Meta-analysisLiao 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. Meta-analysisMocking 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
  5. Silveira JM, Ribeiro TS, Guilarducci MJ, Reis MG, et al. (2024). Effect of fish-oil supplementation on the glycemic and lipidemic profiles of pregnant women: a systematic review and meta-analysis.. Nutrition reviews. DOI PubMed
  6. Khoshnoudi-Nia S, Forghani Z, Jafari SM (2022). A systematic review and meta-analysis of fish oil encapsulation within different micro/nanocarriers.. Critical reviews in food science and nutrition. DOI PubMed
  7. Zhou J, Tang G, Tang S, Yuan W (2022). The effect of fish oil on inflammation markers in adult patients undergoing hemodialysis: A meta-analysis.. Seminars in dialysis. DOI PubMed
Show 1 more reference
  1. Kasawara KT, et al. (2024). The effect of Omega-3 supplementation and fish oil on preeclampsia: A systematic review and meta-analysis.. Prostaglandins, leukotrienes, and essential fatty acids. DOI PubMed