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Bad Side Effects of Omega 3 Supplements

author image Bethany Fong, R.D.
Bethany Fong is a registered dietitian and chef from Honolulu. She has produced a variety of health education materials and worked in wellness industries such as clinical dietetics, food service management and public health.
Bad Side Effects of Omega 3 Supplements
Omega-3 supplements can be beneficial but may cause side effects. Photo Credit: peangdao/iStock/Getty Images

According to the U.S. Food and Drug Administration (FDA), consumption of EPA and DHA omega-3 fatty acids may reduce the risk of coronary heart disease; more research is needed, however. Still, omega-3 fatty acids can benefit heart health, diabetes, lupus, osteoporosis, depression, psychological disorders, skin disorders, eye health, asthma and certain cancers. Omega-3s can be found in foods such as fish, flaxseed and flaxseed oil and walnuts. Bad side effects can occur with omega-3 supplementation despite its many benefits.

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Individuals with bleeding disorders or who take blooding-thinning medications such as coumadin should be cautious when taking omega-3 supplements, according to the University of Maryland Medical Center (UMMC). Medline Plus, a website of the National Institutes of Health, says omega-3 fatty acids increase the risk of bleeding and high doses have been associated with nosebleeds and bloody urine.

Intestinal Discomfort

“Circulation," a magazine of the American Heart Association, published an article about omega-3s in 2003. According to the report, intestinal discomfort, nausea and a bad aftertaste are common side effects of omega-3 supplements, especially in the form of fish oil. Other intestinal side effects of omega-3 supplements are diarrhea, burping, acid reflux and heartburn, bloating and abdominal pain. Medline Plus recommends taking omega-3 supplements with meals to minimize side effects and starting with a lose dose that gradually increases.


According to Medline Plus, multiple studies have shown that omega-3 supplements can cause hypotension, a decrease in blood pressure. Individuals with high blood pressure may benefit from the blood pressure-lowering capabilities of omega-3 supplements but people with existing hypotension or who take medications to lower blood pressure should be cautious.

High Blood Sugar

The UMMC says fish oil supplements high in omega-3s can increase blood sugar and interact with diabetic medications that lower blood sugar. According to Medline Plus, current evidence does not suggest any long-term effects on blood sugar. Still, diabetics should consult a physician prior to taking any supplement.


Fish oil supplements are a source of omega-3s but people with allergies or sensitivities to fish should not take them, according to Medline Plus. Other side effects of fish oil supplements can include rash, abnormal liver function and psychological disorders.

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