Study on fish oil and blood-thinning medication in the American Journal of Cardiology. 2007 Mar 19;99(6A):44C-46C. Epub 2006 Nov 29.  Expert opinion: omega-3 fatty acids and bleeding-cause for concern? Harris WS. Sanford School of Medicine of University of South Dakota, Sioux Falls, South Dakota 57105, USA. bill.harris@usd.edu. Omega-3 fatty acid ethyl esters have well-known triglyceride-lowering properties and were shown >30 years ago to inhibit platelet function. With the recent US Food and Drug Administration (FDA) approval of these agents for treating severe triglyceride elevations, concerns about excess bleeding naturally arise. However, an objective assessment of the evidence for clinically significant bleeding reveals that such concerns are unfounded. As such, the benefits of triglyceride lowering with omega-3 fatty acids more than outweigh any theoretical risks for increased bleeding.

Martie's bottom line: Apparently fish oil works in an different way than the “blood thinners” and the compounding effect some guessed might occur with the drugs didn't materialize. You may need to take this information to your doctor as they may not be aware and otherwise might act out of misplaced concern.

Comment by another expert: Am J Cardiol. 2007 Mar 19;99(6A):44C-46C. Safety considerations with omega-3 fatty acid therapy, Bays HE. Louisville Metabolic and Atherosclerosis Research Center , Louisville , Kentucky 40213 , USA . hbaysmd@aol.com  It has been suggested that the potential antithrombotic effect of fish oils may theoretically increase the risk for bleeding, which may be a safety concern for individual patients. However, clinical trial evidence has not supported increased bleeding with omega-3 fatty acid intake, even when combined with other agents that might also increase bleeding (such as aspirin and warfarin). Another potential safety concern is the susceptibility of omega-3 fatty acid preparations to undergo oxidation, which contributes to patient intolerance and potential toxicity. Finally, large amounts of fish consumption may result in adverse experiences due to the potential presence of environmental toxins such as mercury, polychlorinated biphenyls, dioxins, and other contaminants. The risks of exposure to environmental toxins and hypervitaminosis with fish consumption are substantially reduced through purification processes used to develop selected concentrated fish oil supplements and prescription preparations. Thus, in choosing which fish oil therapies to recommend, clinicians should be aware of available information to best assess their relative safety, which includes the US Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) advisory statement regarding fish consumption, the meaning of certain labeling (such as "verification" through the US Pharmacopeia) and the differences in FDA regulatory requirements between nonprescription fish oil supplements and prescription fish oil preparations, and how all of this is important to the optimal treatment of patients.

Martie's bottom line: Clearly it pays to get a fresh, purified fish oil. That is why I take and recommend Nordic Naturals.