This question is relevant given the fact that the American Heart Association (AHA) recommends fish oil supplements in patients with hypertriglyceridemia after consulting with a physician.2  Furthermore, it is important to note that the AHA also goes on to say that patients taking more than 3 grams per day should only do so only under the care of a physician since high doses could cause excessive bleeding.2  The clinical relevance of this interaction is also important given the fact that such patients are also candidates for aspirin use for cardiovascular (CV) prophylaxis.  Therefore, due to the CV benefits of omega-3 fatty acids, recommendations for their use by the AHA and likelihood that their use will occur in patients taking aspirin or other antiplatelet drug therapy, this issue is of importance for outpatient management as well as surgical admissions.

The National Lipid Association's Nonstatin Safety Task Force analyzed 4,357 patients from 19 clinical trials who took 1.6 to 21 grams of DHA/EPA per day in combination with some type of prescription antiplatelet or anticoagulant; only 1 patient developed heme-positive stool and 1 patient experienced a gastrointestinal bleed.3  It is important to note that these 19 studies represented common CV interventions with 15 trials in patients receiving percutaneous transluminal coronary angioplasty (PTCA), 2 trials in patients receiving coronary artery bypass grafting (CABG) and 2 trials in which patients had endarterectomy.3 

Therefore, the clinical trial evidence to date does not support an increased risk for bleeding in patients taking fish oil supplements or prescription omega-3 fatty acids, even when combined with other medications known to increase the risk for bleeding.  Despite these findings, the NLA Nonstatin Safety Task Force made the following recommendations: 1) In patients taking fish oil along with anticoagulants, it is reasonable to monitor patients for potential bleeding adverse experiences; 2) Fish oils should be discontinued during bleeding episodes such as hemorrhagic stroke; 3) The decision to stop fish oil therapy before an invasive procedure where the patient is at higher risk for bleeding complications should be based on weighing the unproved potential increase in bleeding risk versus the potential reduction in atrial fibrillation before certain procedures such as CABG.4

References:

1. Busti AJ, Nuzum DS, Daves BJ, McKeever GC.  How does fish oil (omega-3 fatty acids; EPA; DHA or Lovazaâ) potentially increase the risk for bleeding or affect platelet aggregation?  PW Nat Med Newsl 2009;1(43):1-5. 
2. American Heart Association.  Fish and omega-3 fatty acids.  Last accessed on 11/01/2015.  
3. Harris WS.  Expert opinion: omega-3 fatty acids and bleeding-cause for concern?  Am J Cardiol  2007;99:44C-46C.  
4. Bays HE.  Safety considerations with omega-3 fatty acid therapy.  Am J Cardiol  2007;99:35C-43C.

Fish Oil, Omega 3 Fatty Acids, EPA, DHA, Lovaza, Fish Oil Antiplatelet Effect