Fish oil

What is fish oil used for?

Updated 4 Nov 2026

Short answer

Fish oil is used for heart health, high triglycerides and other conditions.[1] The evidence is clearest for triglycerides, and many other uses have weak or negative results.[2][3]

What the best reviews found:

  • Triglycerides: about 15% lower, with high-certainty evidence, in a Cochrane review.[2]
  • Heart disease: 9% fewer coronary events in the same review, with low-certainty evidence, and little or no effect on all cardiovascular events, stroke or death from any cause.[2]
  • Blood pressure: 2.6 mmHg lower in the top number at 2 to 3 g a day in one review.[4] The Cochrane review found little or no effect.[2]
  • Pregnancy: 11% fewer preterm births in a Cochrane review.[5] A later trial of 5,486 pregnancies saw no fall in early preterm birth.[6]
  • Joints: a small fall in pain from osteoarthritis, and a limited effect in rheumatoid arthritis.[7][8]
  • Depression: a small effect, unlikely to matter in daily life, with very low-certainty evidence.[9]
  • Fatty liver: better GGT, a liver enzyme, and possibly less fat on ultrasound. There was no significant change in two other liver enzymes (AST and ALT) or in fat measured by MRI.[10]

Trials do not support fish oil for preventing memory decline, for slowing macular degeneration, for ADHD in children or for losing weight.[11][3][12][13] Results for dry eyes are mixed, and a 12-month trial of 535 people found no benefit.[3][14]

Sources (14)

  1. Omega-3 Fatty Acids. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury, 2017. PMID 31644217
  2. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Abdelhamid AS, Brown TJ, Brainard JS, Biswas P, Thorpe GC, Moore HJ, et al. Cochrane Database Syst Rev, 2020. PMID 32114706
  3. Omega-3 Fatty Acids: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov
  4. Omega-3 Polyunsaturated Fatty Acids Intake and Blood Pressure: A Dose-Response Meta-Analysis of Randomized Controlled Trials. Zhang X, Ritonja JA, Zhou N, Chen BE, Li X J Am Heart Assoc, 2022. PMID 35647665
  5. Omega-3 fatty acid addition during pregnancy. Middleton P, Gomersall JC, Gould JF, Shepherd E, Olsen SF, Makrides M Cochrane Database Syst Rev, 2018. PMID 30480773
  6. A Randomized Trial of Prenatal n-3 Fatty Acid Supplementation and Preterm Delivery. Makrides M, Best K, Yelland L, McPhee A, Zhou S, Quinlivan J, et al. N Engl J Med, 2019. PMID 31509674
  7. Effect of omega-3 polyunsaturated fatty acids supplementation for patients with osteoarthritis: a meta-analysis. Deng W, Yi Z, Yin E, Lu R, You H, Yuan X J Orthop Surg Res, 2023. PMID 37226250
  8. Efficacy of n-3 fatty acid supplementation on rheumatoid arthritis' disease activity indicators: a systematic review and meta-analysis of randomized placebo-controlled trials. Gkiouras K, Grammatikopoulou MG, Myrogiannis I, Papamitsou T, Rigopoulou EI, Sakkas LI, et al. Crit Rev Food Sci Nutr, 2024. PMID 35900212
  9. Omega-3 fatty acids for depression in adults. Appleton KM, Voyias PD, Sallis HM, Dawson S, Ness AR, Churchill R, et al. Cochrane Database Syst Rev, 2021. PMID 34817851
  10. Omega-3 polyunsaturated fatty acids and nonalcoholic fatty liver disease in adults: A meta-analysis of randomized controlled trials. Kim SJ, Cho SH, Yun JM Clin Nutr, 2025. PMID 40441053
  11. Omega-3, Omega-6, and Polyunsaturated Fat for Cognition: Systematic Review and Meta-analysis of Randomized Trials. Brainard JS, Jimoh OF, Deane KHO, Biswas P, Donaldson D, Maas K, et al. J Am Med Dir Assoc, 2020. PMID 32305302
  12. Polyunsaturated fatty acids (PUFA) for attention deficit hyperactivity disorder (ADHD) in children and adolescents. Gillies D, Leach MJ, Perez Algorta G Cochrane Database Syst Rev, 2023. PMID 37058600
  13. Does Fish Oil Have an Anti-Obesity Effect in Overweight/Obese Adults? A Meta-Analysis of Randomized Controlled Trials. Du S, Jin J, Fang W, Su Q PLoS One, 2015. PMID 26571503
  14. n-3 Fatty Acid Supplementation for the Treatment of Dry Eye Disease. Asbell PA, Maguire MG, Pistilli M, Ying GS, Szczotka-Flynn LB, Hardten DR, et al. N Engl J Med, 2018. PMID 29652551

More about fish oil

What is fish oil?Does fish oil reduce inflammation?How much EPA and DHA is in a fish oil capsule?Is eating fish better than taking fish oil?Should fish oil be taken with food?Does fish oil prevent heart attacks?

For education; not medical advice. Talk to a doctor before you start, stop or change a supplement.