What Are Potential Fish Oil Side Effects?

On This Page

    Fish oil comes with many benefits. But do they produce side effects? Find out here.

    Fish oil is an abundant source of the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The human body does not produce its own omega-3 fatty acids, but they are essential fats and must be made from foods. Fatty fish such as salmon, tuna, herring, mackerel, and sardines are especially rich in these oils, as are walnuts and flaxseed. They are also sold in supplement form and are available in pharmaceutical grade with a prescription. The primary reason most people take fish oil supplements is for the health benefits linked to omega-3 fatty acids. Though generally considered safe, there can be some potential side effects when taking them.

    Digestive issues

    Digestive issues are not a common side effect with fish oil. A very small percentage of people in certain studies (1%) reported gastrointestinal discomfort such as loose stools or nausea when taking fish oil supplements. A possible explanation is the concentrated fat content when taken on an empty stomach. The best way to boost absorption and avoid digestive discomfort with fish oil supplements is to take them with a meal.

    Bad taste or bad breath

    Much like fish, fish oil can have a distinctive odor that may taste bad and leave an unpleasant taste in the mouths of some who take it. There are also reports of people who claim it causes bad breath or makes their sweat smell bad. While they can be unpleasant, there is no evidence that these side effects are harmful. To avoid any issues with taste, try fish oil in softgels instead of liquid form and always take fish oil with food. If you take several doses of fish oil you can divide the doses throughout the day with different meals. Also look at the other ingredients in your fish oil to make sure there is some form of antioxidants present. Antioxidants such as tocopherols can help maintain freshness and stability of fish oil supplements.


    If you are taking any medication, it is important to talk to your physician about supplements you are planning to take. If you are taking blood thinning medication, fish oil in high doses can be problematic as there is evidence that it can contribute further to thinning the blood.

    This 2013 study demonstrates that fish oil supplementation in healthy individuals reduced platelet aggregation. Platelet aggregation refers to the stickiness of platelets. It is necessary for clotting, most notably in the face of injury. However, too much platelet aggregation at the site of vascular plaques may cause vascular blockage.

    While this 2017 review concluded that the reduction of platelet aggregation was not reflected in increased bleeding risk during or after surgery evaluated in randomized controlled trials, you should always follow your doctor's instructions and discontinue supplementation prior to surgical procedures.

    Allergic reaction

    You should always look at the additional ingredients listed on the label before taking any supplement as potential allergens may be present. If you are allergic to any kind of fish, fish oil is not for you. There are other options that can provide you with a safe alternative source of omega-3s. Care/of’s Veggie Omega is a sustainably sourced vegan product that comes from algae.

    What Is Considered Too Much Fish Oil?

    There are no specific guidelines for the upper limit of omega-3 fatty acids that can be consumed safely. It is recommended that, as a minimum, a healthy adult should consume an 8 ounce portion of fatty fish at least two times each week. When taking fish oil supplements, the U.S. Food and Drug Administration (FDA) found that up to 3 grams daily is “generally recognized as safe” (GRAS). This study did report that there were issues with excess fish oil supplementation during pregnancy, so it is critical to always be aware of how much you are taking in supplement form.

    Fish oil derived from cod liver oil contains high levels of naturally occurring vitamin A, so it is important to monitor intake and be cautious as excess vitamin A can become an issue, especially if pregnant. The tolerable upper limit/intake of vitamin A is reported as 3,000 mcg.

    Care/of has an article, How Much Fish Oil Should I Take, that can answer your questions about supplementing with fish oil.

    Benefits of Fish Oil

    The benefits of fish oil are so numerous that it would seem like a good idea for every person to eat the minimum recommendation of 2 8-ounce servings of fatty fish on a weekly basis. But they don’t, so fish oil supplements are widely used with positive results and good research to back them up. Fish oil supports heart health, brain health, eye health, and joint health.

    Human clinical trials have extensively studied fish oil and how it can help retain healthy triglyceride levels already within normal range while also promoting additional healthy heart markers.

    Fish oil has been studied extensively for its effect on the brain and it appears to be supportive for cognitive health. This study shows that fish oil supplementation improved memory and the reaction time (RT) memory in healthy, young adults whose habitual diets were low in DHA.

    Healthy vision can be supported with high daily doses of omega-3s. This study shows that omega-3s can help to support dry eyes related to computer use. The exact mechanism of action and how omega-3s play a role in tear production need more research.

    Fish oil has been shown to have initial promising results supporting joint health. This 12-month, double-blind, placebo-controlled study found that patients taking 2,600 mg of omega-3 per day experienced less joint discomfort when compared to those taking a placebo.

    How To Manage Side Effects

    Most of the potential side effects that occur when taking fish oil supplements are fairly benign and easily remedied. When combating digestive distress or gastrointestinal issues, it may help to take the fish oil supplement with a meal or at night immediately before bedtime. If that doesn’t work, one might try freezing the fish oil softgels capsules. Sometimes taking a lower dosage and gradually increasing it as it gets more palatable can be helpful, though at other times, stopping supplementing altogether or trying a different brand may be the only thing that helps.

    Care/of has an excellent article, How to Deal With Fish Oil Burping, that explains the cause of this uncomfortable side effect and what to do about it.

    If taking liquid fish oil, try a flavored option or drink some kind of juice to cleanse the palate after intake. It is recommended to also avoid contacting the lips with the oil since that is where the fishy taste can come from.

    Try to make sure there is some kind of antioxidant in your fish oil to maintain freshness and make sure your supplement has not expired.

    Store your fish oil supplement in a cool, dry place.

    The Bottom Line

    Though fish oil supplements are safe, they often come with mild side effects that can be rather unpleasant. Most of them are easily remedied. Try to take fish oil supplements with food if necessary and avoid any ingredients you might be allergic to. Always look for top-quality, premium brands like Care/of’s wild caught Alaskan salmon oil Wild at Heart, a non-GMO, gluten free, C.L.E.A.N. certified, third-party tested fish oil supplement.

    You're unique. Your supplements should be too.

    Take the quiz
    Dr. Carla Montrond Correia ND, CNS
    Medical Content Manager
    Dr. Montrond-Correia is a licensed naturopathic physician and a certified nutrition specialist (CNS). She holds degrees from University of Bridgeport, Georgetown University, and University of Saint Joseph, and supplemented her education with internships in the health and wellness space. She's focused on research, herbal medicine, nutrigenomics, and integrative and functional medicine. She makes time for exercise, artistic activities, and enjoying delicious food.
    Our Editorial Staff
    Freelance Contributor
    The Care/of Editorial Team is made up of writers, experts, and health enthusiasts, all dedicated to giving you the information you need today. Our team is here to answer your biggest wellness questions, read the studies for you, and introduce you to your new favorite product, staying up to date on the latest research, trends, and science. Each article is written by one of our experts, reviewed both for editorial standards by an editor and medical standards by one of our naturopathic doctors, and updated regularly as new information becomes available.