Is It Safe to Mix Fish Oil and Blood Thinners?

By Stephen T. Sinatra, M.D., F.A.C.C., F.A.C.N., C.N.S., C.B.T.

I make no bones about how much I love fish oil. I’ve recommended it for more than 20 years and have seen some great results in people who take it—including improvements in atrial fibrillation, blood pressure, heart rate variability, a racing heart and other arrhythmias. The omega-3 essential fatty acids that fish oil contains help neutralize the effects of Lp(a), reduce arterial inflammation, improve endothelial function, and promote healthier circulation and clotting.

I’ve even been known to say that taking fish oil is “like wrapping the heart in a warm blanket.” Who wouldn’t want that?

But as perfect as fish oil may seem, I’m often asked by people who take prescription blood thinners if it’s safe to combine fish oil with their Plavix or warfarin (Coumadin). They worry that the blood thinning effects of fish oil will interact with their medications and put them at risk for excessive bleeding.

Increased Fish Oil Use Raises Drug Interaction Fears

This is not a new concern, and it was raised again after a study that looked at the use of prescription drugs, OTC drugs, and nutritional supplements appeared in JAMA Internal Medicine.

In 2005–2006, researchers monitored a nationally representative sample of more than 2,000 adults, ages 57–85, to learn how many medications each person, on average, was taking and for what drug interactions the study group was most at risk. (“Medications” were defined as prescription drugs, OTC drugs, and supplements.) In 2010–2011, the researchers repeated the survey with a similar demographic group and compared the findings.

Not surprisingly, they discovered that more people are taking more prescription drugs, with statistically significant increases in the use of statins and antiplatelet blood thinners. They also found an increase in the use of supplements, with a statistically significant uptick in the number of people taking fish oil.

The percentage of people at risk for potential major drug interactions was found to have almost doubled, from 8.4 to 15.1—a jump the research team strongly implied could be due to the increased use of fish oil and blood thinners.

Common Blood Thinners and Anticoagulant Drugs

Fish Oil and Blood Thinner Interaction Realities

I don’t disagree that fish oil and blood thinners—particularly antiplatelet blood thinners—need to be handled with care. The omega-3 fatty acids in fish oil help make blood platelets less likely to clot; antiplatelet blood thinners do the same thing. Too much of both can increase the risk for excessive bleeding from minor, everyday cuts or from the gastrointestinal side effects of drugs like aspirin or NSAIDs, as well as bruising or injuries that may occur as the result of a fall. Blood that is too thin also raises the risk of hemorrhagic stroke, especially in patients over age 85.

Still, the study did not provide any evidence that people taking both fish oil and blood thinners are in imminent danger. In fact, there are no studies that I know of to support such a claim.

There are, however, many studies that demonstrate the cardiovascular benefits of fish oil and omega-3 essential fatty acids on blood pressure, arrhythmias, triglycerides, and arterial health.

How to Safely Take Fish Oil and Blood Thinners

So back to our original question: Is it safe to mix fish oil and blood thinning drugs?

I believe it is, as long as the dosages of all drugs (including fish oil) are managed properly.

Modest amounts of fish oil, say 1–2 grams daily, generally can be tolerated even if you are taking prescription blood thinners. However, doing this is not without some risk—so it’s absolutely essential that you be up front with your doctor about the fish oil products you’re taking and how much, to avoid unsafe drug interactions. I cannot emphasize this enough. You must work collaboratively with your physician and regularly monitor the clotting agents in your blood. (Prepare for the conversation by reading how to talk to your doctor about supplements.) It’s also crucial that you don’t replace a blood thinning therapy that your doctor has prescribed with fish oil, unless that doctor says it’s okay.

Remember, too – blood thinners aren’t limited to prescription medications. Aspirin is also an antiplatelet therapy. If your doctor has prescribed an aspirin regimen for you, you also must tell him or her about your fish oil use. Other supplements can have blood thinning effects, too. These include garlic, nattokinase, vitamin E, ginger, and bromelain.

If you find that fish oil causes your blood to thin too much, use it as an opportunity to ask about reducing the dosage of your prescription blood thinner. But don’t give up your fish oil, unless you absolutely have to. The benefits are simply too great to forego.

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