Fish oil is available as a supplement that manufacturers make from fish. However, the benefits of fish oil are not always clear and can have unexpected side effects.

Certain fish and the oil made from them contain healthy fats that health experts recommend to consume regularly in their diet.

The omega-3s from oily fish and shellfish can play a role in:

The U.S. Department of Agriculture’s 2015-2020 Nutritional Guidelines for Americans recommend eating at least 8 ounces of seafood per week because of these benefits.

Research shows a link between eating fish and health, but studies of fish oil supplements often fail to find such clear benefits.

Read on to learn more about fish oil, the side effects of fish oil supplements, how much is too much, and some of the potential risks.

Share on PinterestIf a person is considering taking fish oil supplements, they should consult their doctor about possible side effects.

The side effects a person can experience from fish oil depend on several factors.

This includes the person’s general health, whether they are taking medications, and whether they have risk factors for fish oil complications.

Most people who take fish oil supplements don’t experience serious side effects.

It’s best to speak to a doctor before taking fish oil supplements, especially if you’re using it for a specific condition.

Bad taste or smell

Fish has a distinctive smell, just like fish oil. Some people report that fish oil tastes bad or leaves an unpleasant taste in the mouth. Others say it causes bad breath or makes their sweat smell bad.

These side effects are the most common that people can associate with fish oil, although there is no evidence that they cause permanent harm.


Fish oil is a natural anticoagulant, which means it can prevent blood from clotting.

This trait can help explain some of its heart health benefits, as thinning of the blood can improve cardiovascular health.

Omega-3 fatty acids can increase the risk of bleeding if a person takes them with certain anticoagulants or medications.

However, a systematic review of 52 previous studies from 2017 found that fish oil reduced blood clotting but did not increase the risk of bleeding in healthy people.

People who use blood thinners such as warfarin should therefore not take fish oil or other dietary supplements with omega-3 fatty acids because of the increased risk of dangerous bleeding.

As with many other dietary supplements and medications, some people experience gastrointestinal problems after taking fish oil. Symptoms can be:

Sometimes reducing the dosage or taking fish oil with food can help. In other cases, a person may need to stop using fish oil supplements.

More rarely, fish oil can cause bleeding in the stomach or intestines and cause or worsen ulcers. This could be because fish oil tends to thin the blood, which increases bleeding.

These serious side effects are more likely to occur with high doses of fish oil or when a person takes the supplement with other medications.

A case study from 2014 focuses on a 60-year-old amateur athlete who consumed 20 grams (g) of omega-3 fatty acids daily. After adding antibiotics and cortisone to the regimen, they developed a bleeding ulcer, although they hadn’t previously had gastrointestinal problems.

The study’s authors said more work was needed to prove the cause.

Allergic reaction

A person can develop an allergy to any food or supplement, including fish oil.

People with allergies to fish or shellfish may be more prone to allergic reactions to fish oil. You should consult your doctor before taking any fish oil supplements.

Prostate cancer

There is mixed evidence for fish oil and prostate cancer.

Some studies have shown that there may be a link between fish oil and prostate cancer risk, while others have come to the opposite conclusion.

A 2013 study of 2,268 older men found that fish oil could slow the progression of prostate cancer. On the other hand, men who ate significant amounts of salted or smoked fish were more likely to develop prostate cancer.

Overall, the researchers found no association between mid-life fish consumption and a person’s risk of prostate cancer.

Share on PinterestThe amount of omega-3 fatty acids a person needs depends on their age and state of health.

There are no specific recommendations on the amount of omega-3 fatty acids a person should be consuming. It depends on a variety of factors, such as your age and health.

Most of the studies on fish oil have looked at small doses of a few grams (g) per day. Higher doses, e.g. B. 20 g per day, can cause more side effects.

People can start on a small amount each day and talk to a doctor before increasing the dose.

If someone notices an offensive odor or other minor side effects, they may want to lower the dosage to see if that helps with the problem.

Anyone who develops serious complications such as allergic reactions, rash, vomiting, or difficulty breathing should stop taking fish oil and seek emergency help.

A 2015 study by the National Institutes of Health estimated that 7.8% of people in the United States take fish oil supplements. Most of them have no serious side effects. Some may even experience significant health improvements.

In addition to the developments fish oil can offer for cardiovascular and brain health, some research suggests that fish oil may aid fetal development during pregnancy. A 2018 study linked fish oil supplements during pregnancy to a lower risk of a child developing allergies.

While data suggesting the benefits of fish oil may seem positive, they are not always conclusive. People looking to improve their health with omega-3 fatty acid supplements should consider adding fish to their diet instead, as the benefits of fresh fish have been more researched.


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