Fish Oil and Atrial Fibrillation: What Trials Found About Rhythm Risk
A plain reading of the meta-analysis and trials that linked marine omega-3 supplements to a higher risk of atrial fibrillation, including what the dose comparison does and does not show.
Content last updated . This page has not been medically reviewed.
Atrial fibrillation (AF) is an irregular heart rhythm. A 2021 meta-analysis of seven large trials found that people assigned to marine omega-3 supplements had a higher rate of newly recorded AF than people assigned to comparison groups. [1] The signal was larger in trials that tested more than 1 g per day. [1] This page describes those findings. It is information, not advice. If you have AF, a family history of it, palpitations, or take heart rhythm or blood-thinning medicines, a clinician or pharmacist should help you decide about any omega-3 product.
Get urgent help (911 in the US) for chest pain, fainting, sudden shortness of breath, or face, arm or speech changes. These can signal a heart attack or stroke, not a supplement question.
How to read the labels on this page
"Established" means a regulator or large body states it. "Mixed" means results differ by product or group. "Insufficient evidence" means too little to say. "Proper evidence not found" means we searched and found nothing usable. Atrial fibrillation here is a clinical outcome; a lab number is not.
What the meta-analysis found
| Question | What the source found | Strength |
|---|---|---|
| Is marine omega-3 linked to more AF in large trials? | The meta-analysis of 7 trials (81,210 patients, weighted average follow-up 4.9 years) reported a hazard ratio of 1.25 for AF (95% CI 1.07 to 1.46). [1] | Mixed to moderate: pooled randomized data, but AF was often an adverse event, not the main goal |
| Does the amount matter? | Hazard ratio 1.49 in trials testing more than 1 g per day versus 1.12 in trials testing 1 g per day or less. [1] | Suggestive; compares trials, not people |
| Per extra gram? | The authors' meta-regression gave 1.11 per 1 g higher dose. [1] | Suggestive |
The authors included trials with at least 500 patients and a median follow-up of at least a year. They left out shorter trials on people who already had AF or AF after heart surgery. [1] So these results do not cover those situations.
What individual trials reported
- REDUCE-IT (purified EPA as icosapent ethyl, 2 g twice daily, in people on statins with high triglycerides): more patients in the treated group than in the placebo group were hospitalized for atrial fibrillation or flutter (3.1% versus 2.1%). [2] The same trial also reported fewer cardiovascular events, so benefits and risks sit side by side. [2]
- OMEMI (1.8 g per day of EPA plus DHA versus corn oil for two years, ages 70 to 82, after a heart attack): a later analysis found new AF or short "micro-AF" episodes in 11.9% of the omega-3 group and 6.5% of the placebo group. [3] The authors reported that change in blood EPA, but not DHA, explained 65% of that association. [3]
- STRENGTH and VITAL: the STRENGTH abstract we read does not report AF, and the VITAL abstract we read reports no excess of bleeding or serious adverse events at 1 g per day. [4] [5] Proper evidence not found: we searched PubMed for the VITAL Rhythm main omega-3 result and could not retrieve it, so we do not state it here.
Limits and uncertainty
- The trials tested different products: purified EPA, EPA plus DHA, carboxylic-acid forms and over-the-counter fish oil. Results should not be carried from one to another.
- The dose comparison is between trials, which differ in people, products and follow-up.
- Why omega-3 may affect rhythm is not settled in the sources we read. The OMEMI authors point to EPA as a possible mediator, which is a hypothesis from one trial. [3]
- The 2017 American Heart Association advisory predates several of these trials. It rated omega-3 supplements as "not indicated" for secondary prevention of AF in people with prior AF and made no recommendation for primary prevention of AF. [6]
Safety and who should ask first
- Tell a clinician if you have AF, palpitations, heart failure, or have had heart surgery, before using any omega-3 product. Ask a pharmacist about medicines that thin blood or control rhythm: medication interactions.
- Do not stop a prescribed medicine, including a prescription omega-3, without your prescriber.
- Tell the surgical team about supplements before procedures: supplements before surgery.
- Product amounts vary by brand and form; see how to read a fish oil label and quality testing.
- For the wider safety picture see omega-3 safety and interactions and prescription omega-3 vs supplements.
Frequently asked questions
Does fish oil cause atrial fibrillation?
A pooled analysis of large trials found a higher rate of AF in people assigned to marine omega-3. [1] A trial result shows an association in those groups; it does not tell any one person's risk.
Is a lower amount safer?
The pooled hazard ratio was smaller in trials testing 1 g per day or less (1.12) than in those above 1 g per day (1.49), but it was still above 1 in the lower group. [1]
Does eating fish carry the same signal?
Proper evidence not found: the trials we read tested supplements, not meals. See oily fish for food information.
Should I stop my omega-3 if I have AF?
The sources do not make that decision for you. Ask the clinician who manages your heart rhythm or your pharmacist. Do not stop a prescribed medicine on your own.
Did the large trials also show heart benefits?
Results differ by product. REDUCE-IT found fewer ischemic events with purified EPA, while a Cochrane review found little or no effect of EPA and DHA on cardiovascular events overall. [2] [7] See omega-3 evidence by use.
References
- Gencer B et al., Effect of Long-Term Marine ɷ-3 Fatty Acids Supplementation on the Risk of Atrial Fibrillation in Randomized Controlled Trials of Cardiovascular Outcomes: A Systematic Review and Meta-Analysis. Circulation 2021. Read 2026-10-22.
- Cardiovascular risk reduction with icosapent ethyl for hypertriglyceridemia (REDUCE-IT). N Engl J Med 2019. Read 2026-10-22.
- Omega-3 fatty acid supplements and risk of atrial fibrillation and 'micro-atrial fibrillation': a secondary analysis from the OMEMI trial. Clin Nutr 2023. Read 2026-10-22.
- Effect of high-dose omega-3 fatty acids vs corn oil on major adverse cardiovascular events in patients at high cardiovascular risk (STRENGTH). JAMA 2020. Read 2026-10-22.
- Marine n-3 fatty acids and prevention of cardiovascular disease and cancer (VITAL). N Engl J Med 2019. Read 2026-10-22.
- Siscovick DS et al., Omega-3 polyunsaturated fatty acid (fish oil) supplementation and the prevention of clinical cardiovascular disease: a science advisory from the American Heart Association. Circulation 2017 (full text read on PubMed Central). Read 2026-10-22.
- Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database Syst Rev 2018. Read 2026-10-22.