8 Little-Known Side Effects of Fish Oil & Why Krill Is Better for You

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Fish oil is well known for a variety of health benefits, and you can find it in most stores. The high content of omega-3 fatty acids makes fish oil a powerful ally in the fight against several serious diseases.

However, taking too much of a good thing can be bad for you, and too much fish oil has been found to cause unpleasant side effects. With krill oil offering the same omega-3 fatty acids in smaller doses, it serves as a great alternative.

What They Don’t Tell You About Fish Oil

Typically to get the benefits in fish oil, larger doses are required, which means it’s easy to take more than is good for you. Understanding the bad side to fish oil will help you keep your doses low and keep you healthy, or lead you towards a healthier alternative.

Elevated Blood Glucose Levels

Supplementing high doses of fish oil can be dangerous for individuals with diabetes, as it has the ability to increase blood glucose levels. The larger doses in fish oil stimulate the production of glucose and after a few weeks, individuals with diabetes register much higher glucose levels.

Acid Reflux

The omega-3s in fish oil are great for boosting heart health, but it can be known to cause heartburn. Acid reflux, along with frequent belching and nausea, are common side effects to fish oil supplements.

Sticking with smaller doses and taking the supplement with a meal helps to reduce these symptoms, but if they persist, you may need to seek an alternative supplement for your omega-3s.


Excess fish oil consumption is known to cause nosebleeds and bleeding gums. High doses have been found to reduce blood clotting ability in healthy adults causing frequent bleeding.

For those taking blood-thinning medications, fish oil should be avoided. You should also stop taking it if you notice frequent bleeding, or lower the dose significantly.


This is a very common side effect of fish oil, especially when taking high doses. It can also cause other digestive troubles such as frequent bloating and flatulence.

Most omega-3 supplements can cause diarrhea, so dosage is important. The smaller the better, and be sure to take the supplement with a meal to ease digestive discomfort.

Low Blood Pressure

While other side effects are unknown, the ability of fish oil to lower blood pressure is well documented. Both systolic and diastolic blood pressure is significantly reduced with fish oil supplementation. This is one of the main reasons people take fish oil, as it helps to lower triglycerides and cholesterol too.

For those with already low blood pressure though, this can be dangerous, and high doses of fish oil supplements should be avoided. It may also interact with blood pressure medications, so be sure to consult with your doctor first.


Despite omega-3s being good at reducing cholesterol and boosting heart health, studies have found that too much can increase your risk of stroke. By decreasing the ability of your blood to clot, too much fish oil can increase your risk for hemorrhagic stroke.

It’s important to note that most studies done so far have been in animals only, but research continues to verify if the risk of stroke is real for people too.

Vitamin A Toxicity

Some fish oil supplements contain vitamin A, and this can be toxic when consumed in large amounts. Most fish oil servings give you 270% of your recommended daily vitamin A.

Vitamin A toxicity presents as nausea, dizziness, joint pain, and skin irritation. In severe cases and over the long term, this vitamin toxicity can cause liver damage and even liver failure.


Small doses of fish oil can help combat insomnia, but too much produces the opposite effect. High doses of fish oil have been found to reduce sleep quality, increase feelings of anxiety, and cause insomnia.

Reduced doses may be beneficial, but again with most fish oil supplements coming in large doses, this can be hard to find.

An Alternative to Fish Oil

With each of these side effects, the problem could be solved in most cases by reducing the fish oil dosage. The trouble with this is that you then limit the amount of beneficial omega-3 fatty acids you get. Higher doses of fish oil are needed to obtain the levels of omega-3s that provide the health benefits you seek. Alternatively, krill oil contains the same essential omega-3 fatty acids in smaller and healthier doses.

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Apart from the smaller but more potent doses, krill oil allows for better absorption of the omega-3s in your body. The fatty acids in fish oil are attached to triglycerides, whereas those in krill oil are attached to phospholipids.

Phospholipids can cross the blood-brain barrier easier and are absorbed into the blood more efficiently, meaning you get the benefits of the omega-3s more promptly. This better absorption is another reason why smaller doses are more powerful.

Krill oil additionally contains a powerful antioxidant known as astaxanthin, which is not found in fish oil. This antioxidant protects the krill oil from turning rancid, which gives it a longer shelf life.

Astaxanthin also works to protect your cells and tissues from oxidative damage and inflammation, which can cause serious disease. The antioxidant also lowers your cholesterol and triglyceride levels, which helps your heart, giving it a further heart-healthy advantage over fish oil.

The Bottom Line

Fish oil has long been known to provide the beneficial omega-3 fatty acids our bodies need. What has not always been known is that there are unpleasant side effects to taking too much fish oil.

Because you don’t want to miss out on the omega-3 benefits, try krill oil instead. The smaller doses give you a healthy amount of omega-3s without the risks that fish oil brings. With the right krill oil supplement, you can have great health, less risk, and you get to avoid that fishy aftertaste too.

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