Do omega-3s cause heart rhythm problems? It’s an important question, especially because omega-3s (EPA and DHA) have one of the strongest track records in natural health for supporting cardiovascular function. We have decades of research and hundreds of clinical trials showing benefits. And yet, between 2021 and 2024, a handful of studies created confusion by suggesting that higher-dose omega-3 supplementation might increase the risk of atrial fibrillation (AFib).

This article breaks down what those studies found, why the results appeared conflicting, what more recent data suggests, and the practical takeaways if you’re using (or considering) omega-3 supplements.

First, what is AFib?

Atrial fibrillation (AFib) is a dysregulation of heart rhythm. It can feel like a fluttering, racing, or irregular heartbeat, and it’s not something anyone wants to develop. AFib can increase the risk of complications like stroke, which is why any suggestion that a supplement might raise AFib risk deserves careful attention.

The controversy: some trials suggested higher-dose omega-3s may increase AFib risk

In 2021, a major analysis looked at randomized controlled trials and found something surprising: omega-3 supplementation, particularly at higher doses, appeared to increase AFib risk in some settings.

The pattern that emerged was dose-related. Trials using high doses (generally over 1 gram per day of combined EPA + DHA) showed a higher relative risk of AFib compared to lower-dose trials. When you translate that into real-world numbers, the increase was reported as roughly a 25% relative risk increase, which corresponded to a small absolute increase (about 0.7%), moving from approximately 3.3% to 4% in overall AFib risk in those trial populations.

That’s enough to raise eyebrows, but it’s also important to recognize the difference between relative risk and absolute risk. A relative increase can sound large, while the absolute change can be modest.

Why this felt so confusing: it clashed with decades of positive cardiovascular research

These findings didn’t exist in a vacuum. They appeared to contradict what we’ve known for a long time: omega-3s have been associated with meaningful cardiovascular benefits across a wide body of research.

In fact, the broader omega-3 literature includes many studies showing improvements in outcomes like:

• Reduced risk of heart attack
• Reduced risk of dying from a heart attack
• Improved cardiovascular risk markers and endpoints

So how could omega-3s be beneficial for the heart, yet potentially increase a heart rhythm issue in some trials?

The UK Biobank data: omega-3 levels were linked to better outcomes

To add another layer, large-scale observational data from the UK Biobank complicated the story in the opposite direction.

The UK Biobank is a massive health dataset, and in a study examining over 200,000 participants (with measured omega-3 levels), researchers found that higher omega-3 blood levels were associated with lower risk of several major outcomes, including:

• Lower all-cause mortality
• Lower heart failure risk
• Lower stroke risk

Earlier UK Biobank analyses also suggested that higher omega-3 levels were linked to lower AFib risk, which looked like the opposite of what some randomized trials were reporting.

Newer clarity: a 2025 UK Biobank analysis found no increased AFib risk with fish oil use

More clarity arrived in December 2025 with an updated analysis using UK Biobank data. In this work, researchers revisited how age and risk were being analyzed and used a more refined approach (treating age as a continuous variable rather than grouping people into simplified categories).

The conclusion: there was no association between fish oil use and an increased risk of AFib. At the same time, the data continued to support a positive relationship between omega-3 status and cardiovascular health, with higher omega-3 levels linked to a lower risk of cardiovascular disease outcomes.

Who may need to be more cautious?

Even with reassuring data, it’s reasonable to take a cautious, individualized approach for certain groups.

Based on the pattern seen in some higher-dose trials, the potential AFib signal appears more relevant when:

• Doses are higher (often discussed as over 1 to 1.5 grams/day of combined EPA + DHA)
• The person is older, especially over 70 to 75+
• There is a history of AFib (or concern about arrhythmia)

If you fall into one of those categories, it doesn’t automatically mean omega-3s are “unsafe” for you. It means the dose and form matter, and it’s worth discussing your specific situation with a healthcare provider.

Form matters: not all omega-3s behave the same

One of the most practical insights from this debate is that some of the studies raising concern used pharmaceutical ethyl ester forms of omega-3s, often at high doses.

Ethyl ester omega-3s can behave differently than more natural forms (such as triglyceride forms). We also don’t fully understand how certain forms and doses might influence heart rhythm. One proposed mechanism is that higher doses could affect the vagus nerve, which can influence rhythm regulation. That doesn’t prove causation, but it’s one reason researchers take the signal seriously enough to keep studying.

So… should you avoid omega-3s?

For most people, omega-3 supplementation still has a strong overall safety profile and a long history of cardiovascular benefits. Many experts who have reviewed the totality of evidence feel that, for people with cardiovascular risk, the benefits of omega-3s outweigh the potential AFib risk, especially when used thoughtfully.

The best middle-ground approach is to focus on appropriate dosing and high-quality forms.

Practical takeaways

1) Aim for a moderate dose range

A moderate daily intake of omega-3s appears to offer cardiovascular support while keeping AFib concerns low for most people. A commonly discussed range is:

• 500 to 1500 mg/day of combined EPA + DHA

2) Choose quality and form carefully

When possible, choose a triglyceride-form omega-3 supplement from a reputable company with strong quality testing standards. Pharmaceutical ethyl ester forms may be appropriate in specific medical contexts, but should generally be used under professional guidance.

3) If you have AFib or are over 70, talk to your provider

If you have a history of AFib, known rhythm concerns, or you’re in an older age group (especially 70 to 75+), it’s worth having a quick risk-benefit conversation with your healthcare provider. In many cases, omega-3s may still be helpful, but dose and monitoring should be personalized.

Bottom line

The omega-3 and AFib conversation is a good reminder that nutrition research can be nuanced. Some high-dose trials raised a legitimate question, but more recent large-scale analyses, including updated work from the UK Biobank, are reassuring and continue to support the broad cardiovascular value of omega-3s.

If you keep the approach practical, use a high-quality triglyceride form, and stay in a moderate dose range, most people can continue to benefit from omega-3s with confidence, while those with AFib risk factors can make a more individualized plan with their clinician.

Educational content only. This article is not medical advice and is not intended to diagnose, treat, cure, or prevent any disease.