Fish Oil Thins Your Blood: True Or False? A Nutrition Scientist Explains

December 28, 2021 — 11:33 AM

When discussing fish oil myths, a few common misconceptions tend to creep up in conversation: Fish oil supplements taste fishy (not if it’s high-quality!); fish oil makes you burp (it shouldn’t!); and you only need 500 milligrams of EPA + DHA per day (actually, research suggests that’s just your baseline, and that 1,000 milligrams [aka 1 gram] and up of EPA and DHA per day offer proportionately greater heart-health benefits*). 

Another common tale? Too much fish oil thins your blood. Here, our director of scientific affairs and in-house nutritionist, Ashley Jordan Ferira, Ph.D., RDN, helps separate fact from fiction. 

It’s a question Ferira previously discussed when it comes to fish oil supplements: Can you get too many omega-3s? It’s a common concern—even propagated by many health care professionals—that extremely high omega-3 intake may contribute to blood thinning and reduce blood clotting.

But according to Ferira, at normal intake levels (like from a fish oil supplement) and even very high levels none of us are consuming, this is nothing more than an old wives’ tale: “The fact is, a quick look at the body of epidemiologic and clinical trial research over the past 30 years demonstrates, from multiple systematic reviews and meta-analyses, that there is, in fact, no increased risk for bleeding when people consume a total daily amount of EPA + DHA as low as 500 milligrams and as high as 10 grams (10,000 milligrams!),” she says regarding omega-3 supplements.

Ferira goes on to say that, “Even if you wanted to be incredibly conservative and apply a random safety factor of 2, and make that daily max 5 grams (5,000 milligrams) of EPA plus DHA, those are not omega-3 levels that supplements provide. Period.”

You see, this link between fish oil and blood thinning began decades ago, due to the fact that omega-3s interact with platelets—which are cell fragments in the blood that play an integral role in clotting.* Over the years, this role with platelets has been blown way out of proportion: “In this case, a textbook physiological mechanism, that omega-3s can impact platelets, has been used to broadly fearmonger against completely safe doses of omega-3s found in supplements,” says Ferira.

“In reality, the blood-thinning effect of fish oil actually occurs at absurdly high levels of EPA plus DHA, 10 grams and up, which by the way, no supplement even comes close to containing. Omega-3 supplements are playing in the 200- to 1,800-milligram range of EPA plus DHA 99% of the time.”

While it is technically possible to get too much of a good thing (even water!), there shouldn’t be too much of a concern with fish oil supplements, especially at clinically efficacious doses. “It’s time somebody debunked this myth that is genuinely scaring people away from using a truly helpful tool (i.e., fish oil supplementation) for whole-body health,”* Ferira adds.