"Smidt Heart Institute researchers have found that taking high doses of fish oil supplements—specifically one gram or more per day—may increase the risk of developing atrial fibrillation, an abnormal heart rhythm disturbance with potentially serious complications. The new study was published today in the peer-reviewed journal of the American Heart Association Circulation.

Atrial fibrillation is the most common type of abnormal heart rhythm, causing the heart to contract irregularly and, sometimes, too quickly. It is estimated to affect 33 million people worldwide and can lead to blood clots, stroke, heart failure and other heart-related complications."

https://www.cedars-sinai.org/newsroom/omega-3-supplements-could-elevate-risk-of-atrial-fibrillation/