What Are the Side Effects of Too Much Fish Oil?

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The human body is amazing. But, it needs continual support to stay healthy. One nutrient that can lend to that support is omega-3 fatty acids. These acids are needed by the body to perform necessary functions such as muscle activity and cell growth, but your body cannot produce this fatty acid on its own.

Fortunately, omega-3s are readily available in most types of fish as well as in some nuts, seeds, and vegetable oils. Plus, there are a growing number of supplements available to support your body’s needs when you are unable to get enough omega-3s from natural sources.

Many people use fish oil to get the omega-3s that they need. And while there are a number of benefits to taking fish oil, it also can produce some mild—and sometimes embarrassing—side effects. Here's what you need to know about the benefits of fish oil, its possible side effects, and how to take it safely.

What You Need to Know About Fish Oil

Fish oil, which typically contains omega-3 fatty acids, is one of the most widely-used supplements in the United States. In fact, according to the 2012 National Health Interview Survey, nearly 8% of adults (18.8 million) and 1% of children ages 4 to 17 (664,000) had taken a fish oil supplement in the previous 30 days.

Most people who take fish oil are doing so because of the numerous health benefits that proponents of fish oil claim the supplement offers. However, the effectiveness, as well as benefits of fish oil, are still being studied.

That said, taking fish oil could help improve symptoms of rheumatoid arthritis and high doses of omega-3s may reduce triglyceride levels. The supplement also has been said to impact mood disorders, prevent heart disease, and slow the progression of eye diseases.

But, for most of these conditions for which omega-3 supplements have been studied, the results are still inconclusive, according to the National Center for Complementary and Integrative Health.

It is also important to note that the Food and Drug Administration (FDA) has prohibited the labels of dietary supplements from including daily intake recommendations higher than 2g. It also has cautioned against consuming more than 3g per day.

If you are considering taking fish oil, speak to a healthcare provider first to determine if this supplement is right for you. You also should be aware of the potential side effects and be mindful of how much you are taking.

Possible Side Effects of Taking Fish Oil

Although fish oil has been touted as having a number of benefits, it also can cause a few side effects. Most of these side effects are mild—and possibly even embarrassing—but usually not harmful. Here are some common side effects of taking fish oil supplements.

Unpleasant Taste

Fish oil is, after all, from fish. If you’re not a fan of the smell or taste of seafood, you may find a liquid fish oil supplement to be unappetizing. To avoid this side effect, you can take supplements in capsule or pill form, but some people even report a fishy aftertaste from these forms as well.

Bad Breath

Similar to the taste, some people claim that fish oil leaves a lasting impact on the odor of their breath, which some people find embarrassing. Freezing capsules can help because it takes longer to break down in the stomach. Taking it with a meal instead of alone also can minimize this possible side effect.

Smelly Sweat

In the same vein as the previous two side effects, people have said that consuming fish oil can give their sweat a noticeable scent. If you work out a lot or tend to perspire easily, you may find this side effect annoying. You can try changing the timing of when you take your fish oil supplement so that it is less noticeable during a workout or reduce the amount you're taking to see if that helps.


Some people have reported headaches as a side effect of taking fish oil, but studies have also shown that omega-3s can be a headache reliever. In fact, taking a fish oil supplement is often a recommendation for people who suffer from chronic migraines. If you experience headaches while taking fish oil, you may want to tell a healthcare provider. 


Due to its fat content, fish oil can trigger heartburn, particularly if you are already prone to acid reflux. Taking fish oil with meals also helps to mitigate the risk of heartburn. Meanwhile, those who have gastroesophageal reflux disease should talk to a healthcare professional before starting a fish oil supplement regimen.

Nausea and Gastrointestinal Discomfort

As a concentrated form of fat, fish oil can disrupt your digestive tract, especially if taken on an empty stomach. General gastrointestinal discomfort, including nausea, is a commonly reported side effect of taking fish oil. Try taking the supplement with food or reducing how often or how much you take to see if that provides some relief.


One review found that the most common side effect of fish oil consumption is diarrhea. Taking it with meals will help to curb this side effect. But, if it continues, lowering your dosage might be a good idea. If you continue to be plagued with diarrhea, talk to a healthcare provider for suggestions, especially if they have recommended the supplements.

Safety and Precautions

One of the biggest cautions against consuming too much fish oil is that it is a natural anticoagulant, which means it prevents blood from clotting. This characteristic can increase the risk of bleeding, and cause your blood to thin.

For this reason, you should be mindful of how much fish oil you are taking as well as consider what other medications you are taking alongside it. Talk to a healthcare provider before taking fish oil to determine if it is right for you. You want to be sure that the fish oil you are consuming does not interfere with your other medications and supplements.

Taking fish oil also can cause you to develop a skin rash. Anyone with an allergy or general sensitivity to fish or shellfish should talk to a healthcare professional before taking this supplement. Even in pill form, fish oil could still trigger an allergic response. 

Talk to a Healthcare Professional

If you have a history of bleeding issues or are on medications that may have similar side effects, like blood thinners, talk to a healthcare provider before adding fish oil to your vitamin and supplement regimen. 

You also should contact a doctor if you develop a rash or any unusual symptoms while taking fish oil. A healthcare provider can help you determine if taking fish oil is right for you.

A Word From Verywell

If you have added a fish oil supplement to your regimen, you may find that you are experiencing some mild—yet annoying—side effects like fishy-smelling breath and sweat. If these side effects are bothersome you can try reducing the amount you consume or try taking them with meals. Sometimes even taking them at different times a day can be helpful.

Also, be sure to talk to a healthcare provider if your side effects are bothersome or get worse. They can help you determine if taking fish oil is right for you.

5 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Center for Integrative and Complementary Health. Omega-3 supplements in depth.

  2. National Institute of Health, Office of Dietary Supplements. Omega-3 fatty acids.

  3. Burch R. Dietary omega 3 fatty acids for migraineBMJ. Published online June 30, 2021:n1535. doi:10.1136/bmj.n1535

  4. Bradberry JC, Hilleman DE. Overview of omega-3 fatty acid therapiesP T. 2013;38(11):681-691. PMID:24391388

  5. National Center for Complementary and Integrative Medicine. 5 things to know about omega-3s for heart disease.

Additional Reading

By Meredith Hirt
Meredith is a writer and brand strategist with expertise in trends forecasting and pop culture. In addition to writing for Verywell Fit, Playbook, and Forbes Advisor, she consults with trend agencies to use data-driven storytelling and actionable insights to help brands solve problems and engage consumers.