What side effects can fish oil cause? Dosage and safety

What side effects can fish oil cause? Dosage and safety

Fish oil comes as a supplement provided by manufacturers from fish. The advantages of fish oil, however, are not always apparent, and can have unintended side effects.

Some fish and the oil from them contain healthy fats that health experts suggest in their diets for people to eat regularly.

The fatty omega-3 acids from fatty fish and shellfish could play a role in:

Because of these benefits, the United States Department of Agriculture’s 2015–2020 Americans Dietary Guidelines suggest eating at least 8 ounces of seafood per week.

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

Read on to learn more about fish oil, the side effects of supplementation of fish oil, how much is too much and some possible dangers.

Side effects of fish oil

Fish oil supplement
If a person is thinking about taking fish oil supplements, they should consult their doctor about any possible side effects.

Several factors depend on the side effects a person may experience from the fish oil.

These include the general health of the person, whether they are taking any drugs and whether they have any risk factors for problems with fish oil.

Most people who take fish oil supplements do not experience any significant side effects.

Before taking fish oil supplements, it is best to talk with a doctor, especially if you are using it for a particular medical condition.

Bad taste or smell

Meat has a distinctive scent, and fish oil, too. Some people complain that fish oil has a bad taste or leaves a nasty taste in their mouth. Others say that it causes bad breath or that its sweat smell is bad.

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


Fish oil is a natural anticoagulant which means that it can prevent clotting of the blood.

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

Omega-3s may increase the risk of bleeding if a person is taking them with a particular anticoagulant or medication.

However, a systematic review of 52 prior research in 2017 found that fish oil decreased blood clotting but did not increase healthy people’s risk of bleeding.

Thus people who use blood thinners, such as warfarin, should not take fish oil or other supplements with omega-3 fatty acids due to the increased risk with serious bleeding.

Gastrointestinal symptoms

Some people may experience nausea when taking fish oil.
Some people may experience nausea when taking fish oil.

Since consuming fish oil, some people experience stomach issues as in many other supplements and medicines. Might include signs of:

Sometimes it can help to lower the dosage, or to take fish oil with food. In other cases , a person might need to stop using additional fish oil.

Fish oil can cause bleeding in the stomach or intestines less often, and can cause or exacerbate ulcers. This may be because fish oil appears to dilute the blood, resulting in increased bleeding.

These severe side effects are more likely to occur with high doses of fish oil, or when someone is taking the supplement with other medicines.

A 2014 case study focuses on an amateur athlete 60 years old who ingested 20 grams (g) of omega-3 fatty acids daily. They also developed a bleeding ulcer after introducing antibiotics and cortisone to the regimen, even though they have no prior gastrointestinal problems.

Study authors said it needed further work to prove the cause.

Allergic reactions

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

People who have allergies to fish or shellfish may be more vulnerable to allergic reactions to fish oil. Before taking fish oil supplements they should consult their doctor.

Prostate cancer

The evidence for fish oil and prostate cancer is conflicting.

Some studies have indicated that there might be a correlation between fish oil and the risk of prostate cancer, whereas others have concluded the opposite.

A 2013 study of 2,268 older men found fish oil could delay prostate cancer progression. By comparison, men who ate large quantities of salted or smoked fish were more likely to develop prostate cancer.

Overall, the researchers found no link between midlife consumption of fish and a person’s risk of prostate cancer.

Fish oil dosage and safety

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

No clear recommendations are made regarding the amount of omega-3 fatty acids that a person should take. It depends upon a variety of factors, such as their age and health status.

Most fish oil studies have looked at small doses of just a few grams ( g) a day. Larger doses, such as 20 g, could cause more side effects per day.

People should start each day with a small dose and speak to a doctor until the dosage rises.

If someone feels an uncomfortable odor or other mild side effects, they may want to lower the dose and see if it helps with the problem.

Anyone who experiences extreme symptoms such as an allergic reaction, rash, vomiting or trouble breathing should avoid taking fish oil and seek emergency assistance.


A 2015 study by the National Institutes of Health estimates that 7.8 per cent of people in the U.S. are taking supplements of fish oil. Many come without significant side effects. Some may even encounter significant improvements in health.

Apart from the cardiovascular and brain health developments that fish oil can bring, some research suggests that fish oil can promote fetal development during pregnancy. A 2018 study ties fish oil supplements to a lower risk of developing allergies in a child during pregnancy.

While there may seem positive data pointing to the benefits of fish oil, it is not always conclusive. People who want to boost their health with omega-3 fatty acid supplements should consider instead adding fish to their diet, as more research is being done on the benefits of fresh fish.