Fish Oil

Side Effects of Cod Liver Oil Capsules

Seven Fish Oil Side Effects

It’s no secret, fish oil is a wildly popular supplement. Almost 18 million Americans have taken a fish oil supplement, and we’d wager if you’re reading this, you’ve either taken it, or are considering it.

Your health care provider may have suggested a fish oil supplement to support your health, especially if you’re needing a boost for your cardiovascular system, but you might still have questions. Together, we’ll talk about what fish oil is, why people take it, and discuss some potential side effects you should know.

Our mission at fatty15 is to make longevity your ally. As such, we’ll talk about how fish oil supports long-term health, and we’ll also talk about an alternative supplement that can support healthy aging, fish-free.

What’s the Scoop With Fish Oil?

Fish oil supplements line the shelves of practically every chain store that has a pharmacy department. With its seemingly endless popularity, it’s easy to assume it’s completely safe and effective. Even if you don’t really know what makes fish oil supplement-worthy, you might find yourself taking it “just because.”

What Is Fish Oil?

Fish oil is exactly what you think it is: oil derived from certain types of fatty fish. Fish like mackerel, salmon, trout, herring, and sardines are all types of fish from which fish oil is harvested and used for making fish oil supplements.

How Fish Oil Harvested

To extract fish oil, fish are heated to near boiling to separate oil, water, and protein. Once these liquid elements have been separated, the oil is centrifuged out, and either cold-pressed or wet-pressed to remove as many impurities as possible. During this process, the “guts” from the fish bodies are removed from the fish oil.

Why Fish Oil Is Used as a Supplement

Discovering how fish oil is extracted is, admittedly, a little off-putting. It will also make you question just why you’re consuming boiled fish parts in the name of good health.

Fish oil is a rich source of omega-3 fatty acids. Omega-3s can help support healthy, low blood triglyceride levels that can lead to a happier, healthier heart. They’re also used to support joint and bone health, helping support patients who suffer from rheumatoid arthritis and other bone and joint disorders.

Lowering triglycerides and improving joint pain can significantly improve a person’s wellbeing if they suffer from these conditions, but it’s worth noting that fish oil is only a supporter and isn’t meant to replace other medications or management methods.

What’s Inside a Fish Oil Supplement?

Fish oil contains two fatty acids, known as docosahexaenoic acid, or “DHA,” and eicosapentaenoic acid, or “EPA.” Neither of these polyunsaturated fatty acids are the essential omega-3, which is alpha-linolenic acid (ALA), but they’re still fairly good for you.

Essential means our bodies need the nutrient to function, but we can’t make enough of that nutrient on our own and need to consume it through diet or supplements.

That said, most of the time, you’ll get omega-3s through the foods you consume. Cod liver oil, flaxseed oil, chia seeds, walnuts, soybeans, oysters, and multiple types of fish contain omega-3 fatty acids.

The problem with many fish oil supplements is that they contain some fishy ingredients. Blends of different fish oils, questionable preservatives, and some synthetically created oils marketed as fish oil are all apt to find their way into your medicine cabinet. This may leave you wondering whether taking a fish oil supplement is worth the risk.

Seven Side Effects of Fish Oil Supplements

Before you decide whether or not fish oil is a good fit for your health stack, you should be aware of the risk of side effects. Although fish oil supplements can support heart health and tender joints, too much fish oil can actually have a negative impact on your health.

1. High Blood Sugar

High doses of omega-3s have been linked to an increase in blood sugar levels. Omega-3s trigger the release of glucose, so in a patient who already has elevated blood sugar levels, this could be incredibly problematic and make it difficult for them to regulate their blood sugar efficiently.

Unchecked, high blood sugar levels can contribute to insulin resistance and affect diabetes management.

2. Gastrointestinal Upset

It’s widely known that fish oil capsules can give you a fishy aftertaste in your mouth, fish breath, and the dreaded fish burps. Even capsules marketed as “burpless” aren’t really able to conceal that they do, in fact, still have the potential to create gastrointestinal upset. Generally, capsules that can upset your stomach are synthetically created.

Taking higher doses of fish oil can result in digestive issues like:


Heartburn and indigestion

Excessive burping

Stomach discomfort



If you experience any of these side effects, it’s recommended to stop taking your supplement and contact your doctor.

3. Low Blood Pressure

If you have high blood pressure, the thought of lowering your numbers through the use of a supplement sounds like a win. However, if you have healthy blood pressure to begin with, lowering your blood pressure may not be the best route to take. If you have low blood pressure, you could risk experiencing dizziness, fainting, and lethargy.

4. Bleeding

A few weeks into taking your fish oil supplement, you suddenly develop a nosebleed for the first time since grade school. Is it related? Possibly, and worth considering as bleeding gums and nosebleeds are known side effects of taking a fish oil supplement.

It’s worth noting that people who experience bleeding from fish oil supplementation are usually taking extremely high doses. Because of the effect fish oil has on blood clotting, your doctor will advise you to stop taking it if you have an upcoming surgery.

5. Toxicity

Some fish oil supplements are high in vitamin A. Cod liver oil, for instance, is a rich source of both omega-3 and vitamin A. Taking too much of a vitamin A supplement can result in vitamin A toxicity.

Symptoms of vitamin A toxicity include:



Joint pain

Rash or hives

If you’re using a cod liver oil supplement long-term, be sure to discuss your liver health with your doctor. High levels of vitamin A can be damaging to your liver health.

6. Insomnia

Sleeplessness may not seem like a big deal if you only miss a night or two of good sleep. Long term, though, the effects of not getting enough sleep can be incredibly detrimental to your health. As such, it’s critical to ensure you’re not taking a supplement that could interfere with your sleep hygiene.

Taking too much fish oil can interfere with sleep, and if you already have sleep issues, it may make them worse.

7. Stroke

While many people begin taking fish oil supplements to support their hearts after a diagnosis of coronary heart disease, there’s some debate as to whether or not too much fish oil could cause weakened blood vessels that could lead to stroke.

Whether or not high levels of fish oil can lead to stroke is still in research, but if you are at high risk of stroke, it may be better to talk to your doctor about taking a different heart-healthy supplement.

A Better-Backed Supplement

So much fish, so many side effects. Wouldn’t it be great if you could support your health with a less fishy supplement? The good news: you can.

C15:0, also known as pentadecanoic acid, is an odd-chain, saturated fatty acid that science supports as the first essential fatty acid to have been discovered since the omegas.

Elevate your cells. Elevate your self. Buy Now

Where Does C15:0 Come From?

C15:0 is found mostly in whole-fat dairy products, like full fat butter and whole milk, as well as some types of fish and plants. That means you may not be getting much of it in your diet. Outdated dietary guidelines (from the 1970’s) have had us avoiding dietary fat, but as it turns out, not all fats are bad. In fact, some fats, like C15:0, are really good for us.

What Does C15:0 Do?

C15:0 is a sturdy essential fatty acid that helps support our bodies on the cellular level.* By supporting our cells, C15:0 gives them a fighting chance against aging.

Here’s how it works:*

Cell membrane support. As we age, our cell membranes become weak, leaving our cells vulnerable to external stress. C15:0 integrates itself into our cells’ membranes, fortifying them and keeping them strong and protected. Improved mitochondrial function. Our mitochondria power our cells to carry out everyday cell processes. As we age, our mitochondrial function naturally declines. C15:0 boosts mitochondrial function by up to 45%, helping to give us back the feelings of menergy we had when we were younger. Improved cellular signaling. By activating special receptors in our body called PPARs, C15:0 helps support homeostatic functions like sleep, mood, appetite, and metabolism, helping to put your body back into balance so you can feel your best every day.

Every system, organ, and tissue in your body is made of cells. When your cells are healthy, your body is healthy. Taking C15:0 to improve your cellular health is a scientifically backed way to support your overall health, and it takes just one capsule a day.*

How To Get C15:0

There are a few reasons why taking a supplement to obtain this essential fatty acid may be beneficial.

First, it's made ready-to-absorb. In milk (and other foods), C15:0 is attached to branches of lipids called triacylglycerides. That means our gut has to use digestive enzymes to break down these triacylglycerides to release C15:0 as a free fatty acid. Once C15:0 is released, it is ready to be absorbed.

These multiple steps can make our absorption of C15:0 from foods less efficient.

In contrast, FA15™ in fatty15 is our proprietary pure, powder C15:0 ingredient already in free fatty acid form. Less work for the gut, more good C15:0 for our bodies.

It's not mixed with bad saturated fats. While the good C15:0 fatty acid is present in whole fat dairy products in trace levels, there are much higher levels of “bad” even-chain saturated fatty acids that continue to be associated with poorer health. That is probably why studies evaluating the effects of milk on our health are mixed (some say dairy fat is bad for us, while others say it is good for us).

Fatty15 provides just the good fat without the bad fats.

It skips the cows and calories. Whole fat dairy products provide a wallop of calories, including sugars (aka lactose), that also require, well, cows. The calories in whole fat milk likely explain why a large-scale recent study showed that adults who drink more dairy milk are more likely to have a higher body weight.

Further, the movement to more plant-based milk and meat replacements are driven by a desire for more animal-free products, as well as a desire to veer from cows and cattle because of concerns around methane production. Interestingly, plant-based milk replacements lack C15:0 altogether.

Fatty15 offers a vegan-friendly C15:0, with only 1 calorie per dose.

Fatty15: A Fish-Free Approach to Your Health Stack

Fatty15 is the once-a-day supplement that contains the pure, vegan-friendly version of C15:0, and nothing else. Just one simple ingredient is enough to support your cells, restore your essential C15:0 levels, and help you feel healthier and age smarter.*

Get started with fatty15 today and support more than just your heart, fish burps-free.


Omega-3 Supplements: In Depth | NCCIH

The Slippery Facts about Fish Oil|Review of

Elevated plasma glucose and lowered triglyceride levels from omega-3 fatty acid supplementation in type II diabetes|PubMed

Fish Oil Diet Associated with Acute Reperfusion Related Hemorrhage, and with Reduced Stroke-Related Sickness Behaviors and Motor Impairment|PubMed

Fish Oil Side Effects: 4 Tips To Avoid Them

Want the secret to getting the most out of Omega-3s? Get our free report

OK – you tried fish oil because it’s good for you.

Now you’re experiencing some minor fish oil side effects.

This is normal.

Especially if you just started taking fish oil for the first time.

The most common fish oil side effects are belching and fishy aftertaste.

List of common fish oil side effects:

Fishy burps or belching

Stomach upset



Unpleasant taste in mouth

List of uncommon fish oil side effects:

Skin rash

Back pain

Flu-like symptoms

Minor infection

All of the side effects listed above are temporary.

Do not take fish oil supplements if you are allergic to fish or soy.

Why soy? Because some of the other ingredients in the pill may be made from soy. OmegaVia does not contain soy.

If you notice difficulty breathing, hives, swelling of tongue, lips or throat, get emergency medical help at once. These are signs of allergy. You may be having an allergic reaction to fish oil or something else that you just ate.

How common are these fish oil side effects?

Most people will notice burping or belching when they first start taking fish oil. This can be minimized if you take your fish oil with food. It also helps if you take only one pill per day at first and increase the number of pill gradually.

About 30% of people taking fish oil pills will experience one of the minor fish oil side effects.

About 4% of people stop taking fish oil because of side effects.

About 3% experience an unpleasant taste in their mouth.

About 8% experience an upset stomach.

About 2% experience back pain.

About 3% experience minor flu like symptoms.

About 5% experience minor infection.

In a clinical study, 41 people took 6 fish oil pills a day for almost 3 years. Of the 41, only 3 dropped out because of the side effects.

The Food and Drug Administration (FDA) says it is safe to take 3 grams (usually 3 pills) per day.

If you take blood-thinners or anti-coagulants like Coumadin®, talk to your doctor as high doses of fish oil can act as a natural blood-thinner.

Overall, fish oil side effects are minor and harmless. Benefits of taking fish oil supplement far outweigh any of the side effects.

4 Tips to reduce fish oil side effects

Take only ultra-concentrated fish oil. One ultra-concentrated fish oil pill has as much Omega-3 as three regular fish oil pills. With ultra-concentrated fish oil, you get more benefits with fewer pills. And fewer pills mean fewer side effects.

Shopping tip: How do you know if your fish oil is ultra-concentrated?

Look at the Omega-3 content. It should be above 75 or 80% Omega-3. Most fish oils sold in retail stores are not ultra-concentrated. Retail fish oils are usually only 30% Omega-3. The other 70% is miscellaneous fat that is not listed on the product label. Some retail fish oil can be as high as 50% Omega-3 but the other 50% is just fat. Start small. If you are just starting to take fish oil, take one pill per day. After a few weeks, increase dosage to two per day to feel more benefits. If your body is not used to fish oil, taking too many pills at once can cause diarrhea. Take with meals. This always helps with reducing side effects like burping and belching. Some people also find that freezing the pills reduces burps. Buy Enteric-coated fish oil. Enteric coating prevents the pill from dissolving in the stomach. The pill stays intact well into the intestines. Once fish oil is in the intestine, you can’t burp it back up.

Bottom-line: you may experience some minor fish oil side effects but there are ways to reduce the effects. The overall benefits of fish oil are so great that it is worth understanding and coping with the occasional small discomforts.


GISSI Prevenzione Trials

Medline Plus – US National Library of Medicine

Side Effects of Cod Liver Oil Capsules

Common cod liver oil side effects include bad breath, an upset stomach, headaches and a metallic taste in your mouth. Image Credit: Photo by Cathy Scola/Moment/GettyImages

Cod liver oil capsules are dietary supplements rich in vitamin D, vitamin A and omega-3 fatty acids. They are a great source of supplemental nutrition, but can also cause some mild side effects, like bad breath and nausea.


Tip Common cod liver oil side effects include bad breath, an upset stomach, headaches and a metallic taste in your mouth. If you experience more severe side effects, like an allergic reaction, seek out medical attention immediately.

There is also the potential for more serious cod liver oil side effects like an allergic reaction or changes to your vision. Plus, cod liver oil pills may interact with medications you are taking. If you experience severe side effects, stop taking the supplement and seek medical attention right away.

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Cod Liver Oil Pills

Cod liver oil pills are dietary supplements that provide vitamin A, vitamin D and omega-3 fatty acids. These nutrients occur naturally in food and play a variety of important roles in the body. However, since dietary supplements are not regulated by the U.S. Food & Drug Administration, it's not a given that the capsules contain what the ingredients list says, and health claims may not be true.


Vitamin A helps build and maintain healthy skin, teeth, mucus membranes, soft tissue and skeletal tissue. It also plays a role in eyesight.

Vitamin D helps the body absorb calcium, which is used to build and maintain bones. Low vitamin D levels have been linked to an increased risk of high blood pressure, heart attack, heart failure, stroke and diabetes. In pregnant people, low vitamin D is associated with pre-eclampsia and gestational diabetes.


Omega-3 fatty acids are used in cell membranes and help with making various hormones that regulate blood clotting and how the walls of your arteries contract and expand. They may also decrease inflammation. The Harvard T.H. Chan School of Public Health explains that your body cannot make or store omega-3 fatty acids, which necessitates regular dietary intake.

The three main omega-3s are alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). According to the National Institutes of Health Office of Dietary Supplements, ALA is found in plant oils while DHA and EPA are found in fish and seafood.


Cod Liver Oil Benefits

One teaspoon of cod liver oil provides 41 calories, 1,350 micrograms of vitamin A retinol activity equivalents (RAE) and 450 international units of vitamin D. It also provides 4.5 grams of fat, of which over 1 gram is polyunsaturated and over 2 grams are monounsaturated. Many people prefer to take cod liver oil capsules rather than taking it by the spoonful, due to the oily, fishy taste.



Many of the purported benefits of cod liver oil are due to the presence of omega-3 fatty acids. However, the National Institutes of Health Office of Dietary Supplements says the link between omega-3 fatty acids and cardiovascular health is complicated. While increased consumption of seafood may lower cardiovascular health risks, supplemental omega-3s may not provide those same benefits.

A meta-analysis of omega-3 fatty acid supplement use, published in the March 2018 ​JAMA Cardiology​, reviewed 10 clinical trials involving 77,917 participants. It found no significant association between omega-3 fatty acid supplements and fatal coronary heart disease, nonfatal coronary heart disease and major vascular events.


The meta-analysis found no support that omega-3 fatty acid supplements could help people who have coronary heart disease. Instead, the American Heart Association recommends consuming omega-3s from fish and other seafood.

​Read more:​ Benefits of Cod Liver Oil

Cod Liver Oil Side Effects

The Mayo Clinic says that fish oil is generally safe when taken as recommended. When taking cod liver oil, side effects range from mild to severe. The common side effects typically don't require medical attention, unless they last much longer than expected or begin to bother you. These include:


Bad breath



A metallic taste in the mouth

An upset stomach

There are some more serious side effects. The Cleveland Clinic recommends speaking to a doctor as soon as possible if you experience any of the following after taking cod liver oil capsules:

Allergic reactions such as skin rash, hives, itching, or swelling of the lips, face or tongue

Yellowing of your skin or eyes

Bleeding or bruising

Dark urine

Vision changes



​Read more:​ Benefits and Risks of Fish Oil Supplements

Cod Liver Oil and Medication

Another potential side effect: Cod liver oil may interact with medications you are taking to treat other health conditions. According to MedlinePlus, be cautious about potential interactions with:

Antihypertensive drugs, taken to decrease high blood pressure. Cod liver oil may also decrease your blood pressure, causing it to become too low. Common medications for high blood pressure include amlodipine, captopril, diltiazem, enalapril, hydrochlorothiazide, losartan and valsartan.

Anticoagulant medications, taken to slow down blood clotting. Because cod liver oil can also slow down blood clotting, it may increase bruising or bleeding when combined with medications like aspirin, clopidogrel, diclofenac, dipyridamole, enoxaparin, heparin, ibuprofen and more.

If you take prescription medications, it's a good idea to speak with your doctor before adding any dietary supplements like cod liver oil to your regimen. You can ask about any potential drug interactions or side effects.

Breath and Cod Liver Oil

There are a few different things you can try if you experience bad breath after taking cod liver oil pills. One option is to take the cod liver oil capsules with food, either with a meal or a healthy snack. In particular, a meal with healthy fats like avocado or nuts may help you digest the capsules more quickly, preventing fishy breath or burping.

If taking the capsules with meals makes no difference, you might try a different brand of cod liver oil or a lower dose. You can also stop taking the supplements entirely and try to get sufficient omega-3 fatty acids from dietary sources.

Foods rich in the omega-3s eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) include:






Sea bass


In addition, seaweed and algae are two of the few plant foods that contain EPA and DHA. That makes them an excellent dietary addition for vegetarians and vegans who cannot eat fish or seafood.


Eric Carter