What Are the Side Effects of Fish Oil Supplements?

Updated on December 7, 2016

Fish oil supplements have become a highly recommended supplement. It has been suggested that they can help treat dyslexia, ADD, ADHD, heart disease, bipolar disorder, high blood pressure, rheumatoid arthritis, asthma, depression, and even cancer. While some of these claims are well supported by research, not all of them are. Nonetheless, it is clear that there can be benefits to taking fish oil supplements, because none of us gets the full benefit from the foods we eat.

Fish oil comes from the fat of fish. That's pretty simple, but many of us don't eat fish very often. In fact, with today's pollution issues, many of the fish that are supposed to be healthy may not actually be very good for us to eat too often due to the risk of heavy metal poisoning. That leaves supplements as a much safer way to take advantage of fish, without the dangerous heavy metals.

But what are the side effects of taking fish oil supplements?

Consult Your Doctor

Always consult your doctor before taking a new supplement or vitamin.

Very Common Side Effects

Digestion issues is the biggest complaint of people taking fish oil supplements. This can include a wide range of discomforts including diarrhea, upset stomach, burping, acid reflux, heartburn, indigestion, abdominal bloating, abdominal pain, and a fishy after taste. In most cases these aren't serious problems though they do cause discomfort. There are a few things that are recommended to help avoid these issues when you start taking fish oil supplements.

  1. Always take them with a meal. This helps eliminate some of the burping, the fishy after taste, and often helps them digest better (making it less likely that you will experience bloating and abdominal pain).
  2. Start at the lowest dose possible (usually one capsule a day) so that your body gets used to digesting the fish oil and then increase slowly to the amount you desire to take each day.
  3. Choose a capsule form and avoid liquid forms since liquid hits your system all at once and is going to make it harder to digest quickly.
  4. Buying a better quality of fish oil supplement is also supposed to help. Not all supplements are equal.

More Serious Side Effects

While no one wants to deal with indigestion and issues surrounding it, it really isn't serious. There aren't many serious side effects of fish oil, however there are some that occur when large doses of the supplement are consumed. There are also some easy ways to solve these problems and make sure that you don't suffer from them.

Taking too much- Taking too much fish oil supplement is relatively easy to do. There is no "daily allowance" and each company has their own suggestion as to how much you should take. If you do take large doses of fish oil for an extended period of time you are at risk for bleeding problems. You may get nose bleeds or notice blood in your urine. Your platelets will have trouble clotting and you could even end up having a stroke. So, it is important that you don't take too much, especially for too long.

How much is too much? That's the scary part. We really aren't sure because there isn't a maximum amount that you should take. However it is recommended that men take 1600 mg and women take 1100mg a day. Aim for something just under this number. The only time you should take more then that amount is if your doctor tells you to, as he or she will be monitoring your condition.

Vitamin E overdose- Vitamin E is a fat soluble vitamin. The digestion process of fish oil often uses vitamin E and can tax the system and deplete vitamin E resources. To eliminate this issue most fish oil products contain vitamin E. If you are also taking other vitamin E enriched products you can get a vitamin E overdose.

Making sure it doesn't happen to you. Read all labels clearly and know what you are taking with each enriched product. Choose them carefully and know that you are not exceeding recommended levels of Vitamin E. You can find fish oil supplements without Vitamin E or choose your other supplements and vitamins to meet your needs, but not exceed them.

Vitamin A and D overdose- Fish oil made from cod liver (or other fish livers) are often advertised as being even better for you then fish oil. While it is true that fish liver oil has more of the nutrients that are good for you, it also has vitamin A and D. The problem here is that these fat soluble vitamins are a huge part of our daily lives. We get them in the milk we drink, we get Vitamin D from the sun, we get them in our daily multivitamin and with all these sources it is easy to overdose on vitamin A and D.

Making sure it doesn't happen to you. You can avoid a Vitamin A and/or) D overdose by avoiding fish oil supplements made from fish liver.

Are There People Who Shouldn't Take Fish Oil?

Most who support fish oil and its consumption would have you believe that it is the perfect supplement for everyone and will help with a lot of common issues. It is supposed to give you energy and make you feel even better then before. But there are people who should avoid it for a variety of reasons.

Allergies- Those who are allergic or hypersensitive to fish should avoid fish oil. The chances that they will have an allergic reaction to the supplement is very likely and this could be dangerous for some.

Low blood pressure or on blood pressure medications- Those who struggle with low blood pressure or those on blood pressure lowering medications should avoid fish oil. One of its side effects (or benefits depending on who you are) is that it lowers blood pressure. If you have low blood pressure or are on medications to lower your blood pressure it is possible to cause it to drop too low.

High cholesterol- Fish oil causes an increase in Lipoprotein Levels (bad cholesterol). Because of this it isn't recommended for those with high cholesterol levels.

Diabetics- While there is some research that shows that fish oil is safe for diabetics it does seem to cause a rise in blood sugar levels, at least at first. While it may be safe for them to take it, it should be cautioned.

Children- There are a few different issues that are a problem for giving fish oil supplements to children. First, dosing should be done by weight and getting it right can be hard to do. Overdose can be easy and problematic. Additionally, while research shows that the process for obtaining fish oil eliminates most heavy metals (if not all) there is still a chance that there will be low doses of heavy metals in the fish oil which can be a much larger problem for children then adults.

Pregnant and breastfeeding women- Similarly because there is a risk of some heavy metals occurring in fish oil supplements they should be avoided by pregnant and breastfeeding women.

Abnormal heart rhythms- Finally those with abnormal heart rhythms should avoid fish oil because it is unsure as to how it will affect them and could do so dangerously.

Overall, the National Institute of Health has stated that low doses of fish oil supplements are "generally regarded as safe". Nonetheless, if you have any of the above you should probably skip out on the "magic pill". Additionally, whether you are healthy or not it is a good idea to talk with your doctor before beginning any vitamin, dietary supplement, or herbal remedy.

Not All Supplements Are Equal

If you go to the vitamin and supplement aisle of your local store you may feel a little overwhelmed by bottle after bottle of choices. Choosing one can be difficult. There are some who go in and feel that whatever they pick up is going to do what they want. However, supplements aren't something that are regulated by the FDA. This means that you could be choosing something dangerous. So, when looking at all those bottles how do you choose the one that is the best and that is right for you? Follow these tips for choosing a good supplement.

  1. USP Certified! The USP certification stamp (or US Pharmacopedia stamp) shows that the product and company have been tested by a third party (the US Pharmacopedia themselves). They are stating that the bottle contains what is listed on the label (not all supplements do), it doesn't contain any harmful contaiminents (some supplements do), it will break down in the system and release the supplement to the body, and that the product was manufactured with good practices. Always choose a product that has the USP certified stamp.
  2. The product should also contain a list of ingredients. If there is a recommended daily allowance it should include a percentage of that daily allowance. With fish oil there isn't, so you should look for an amount that each dose has (pay attention to your dosage size because it could be as many as 2-4 capsules). That way you can make sure you aren't going to overdose.
  3. Ignore all medical claims made on the bottle. Many of these are just advertisements and not supported by research. One bottle of fish oil supplements isn't going to be better then another because of the claims on the bottle.
  4. Check the shelf life and make sure you are getting a product that will last all the way through. Try getting one that has at least a year left. Never use supplements past their shelf date.
  5. While fish oil is available in a capsule and a liquid form it is often easier for most to handle in a capsule form. It causes a lot less issues. Under normal circumstances you should choose a chewable form of the supplement as the best option because it breaks down best in the system.

Be Careful With Your Research

Researching supplements and other "home remedies" is always a good idea before you actually begin taking them. However, it is important to know where your information is coming from. There are many sites out there that look like good places for information. They will tell you all the benefits of a supplement (in this case, fish oil), and they will tell you that there are no side effects or that the only side effect is "a fishy aftertaste". Usually these pages conclude with a link to where you can buy the supplement. Always be a little wary of a page that ends with a link. That means they are making money selling you the supplement. It also means that they are advertising and trying to get you to buy it, rather then dishing out the truth, the whole truth, and nothing but the truth.

Final Thoughts

Fish oil supplements are good for a lot of people. You just need to take some precautions, have a little knowledge under your belt, and make sure that you don't fall into a group of people who should avoid them. It is always a good idea to talk to your doctor about taking supplements before you do it. This can help you avoid interactions with your medications, with other supplements you are taking, and will let your doctor know what you are doing to help your health. He or she can also help make sure that everything is going well.

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.


Submit a Comment
  • daviddwarren22 profile image


    8 years ago

    Hi aiden- Never knew about side effects of using fish oil before.Thanks for this great information.

  • profile image


    8 years ago

    I put the approved bottle of fish oil capsules in the freezer and this stops the fish taste burp which I didn't like. My respected cardiologist has me on 4,000 mg a day -something that he himself takes.

  • aidenofthetower profile imageAUTHOR


    8 years ago

    @S. A. Smith...

    The first thing I want to say is that you should talk about all your symptoms and your concerns with your doctor. I have done a lot of research on fish oil, but am not qualified to give you real medical advice. You should make sure your doctor knows you are taking fish oil and find out if it could be causing your issues or it could be interfering with your medication. Indigestion is very common when taking fish oil and it really could be causing it. If your doctor isn't the one who told you to take fish oil supplements then I would recommend discontinuing use and talking with your doctor about it. Do not stop taking your other medications. Even if fish oil is increasing your cholesterol levels you should take your medication until you have talked with your doctor.

  • profile image

    S. A. Smith 

    8 years ago

    Hi--I started taking fish oil a while back (two 1000 mil. per day). In March, I was diagnosed with high cholesterol, acid reflux, and arthritis. The doc put me on Zocor for the cholesterol, Nexium (for 30 days) for the indigestion, and Aleve for the arthritis pain. As long as I took the Nexium, the indigestion was non-existant, but since then, the indigestion has come back. After reading your article, I am wondering if I am a candidate for stopping fish oil use. Could the fish oil possibly be causing the high cholesterol reading and the indigestion?? I have tried taking it with food. I also had rhuematic fever as a child without any heart involvement, but lately I have noticed that my heart rhythm seems a little off at times.

  • marimccants profile image


    9 years ago

    NIce hub! Lots of useful information. Thanks for posting.

  • AKN-London profile image


    9 years ago from UK

    I use to think that Fish oil is healthy because of Omega 3 with no side effects but now i believe don't start any medication without asking your doctor! Thanks for that!

  • profile image

    Car Donations 

    9 years ago

    Hey, great hub. I have some advice. If you have ever burped after taking fish oil, you probably get a nasty taste in your mouth. I keep my fish oil in the refrigerator. It seems to reduce the odd taste. It works. Try it. No more burps that taste like vomit. lol

  • Dr. Wendy profile image

    Dr. Wendy 

    9 years ago from Kentucky

    Excellent hub. Very informative!

  • profile image


    9 years ago

    Thank you. I will be seeing him in a week and will ask then

  • aidenofthetower profile imageAUTHOR


    9 years ago


    I have never heard of this being an issue. However, you could have a sensitivity to it or even an allergy. I would highly (highly) recommend talking to your doctor about it. With his or her help you should be able to find out why you are having problems and what you should do. Because you are taking fish oil for a very serious problem by the orders of your doctor I wouldn't recommend discontinuing use! You should keep taking them as recommended and call your doctor as soon as possible.



  • profile image


    9 years ago

    I remember reading about nondigestable oils being used to cook fried foods with the ultimate result being they passed through your body and leaked out through your anus. They apparently were too small to be held by your body. I have noticed something happening to me that seems related to this phenomenum. I am taking 4000 mgs of fish oil daily on drs orders to help control high blood pressure. Is this something that is a problem that has been reported before or should I look for some other cause?

  • profile image


    10 years ago

    This is a good post

  • DynamicS profile image

    Sandria Green-Stewart 

    10 years ago from Toronto, Canada

    aidenofthetower, thanks for this useful information. I did not know that I could get vitamin e & d overdose taking fish oil. I currenlty take 1000 unit of vitamin d during the winter, but i'll ne sure not to take both vit d and fish oil together.

    Great hub!

  • SandyMcCollum profile image


    10 years ago

    A great piece! Good information and well written. I give fish oil to my dog as part of his skin treatments. Noticed a BIG difference quickly! Write on!

  • Sexy jonty profile image

    Sexy jonty 

    10 years ago from India

    Very well written hub .....

    very much informative ......

    Thank you very much for your great hub, for good advice, good wishes and support. Thanks for sharing your experience with all of us.

  • JPSO138 profile image


    10 years ago from Cebu, Philippines, International

    I know that anything taken in excess will surely create problems. Surely you have clarified this matter. Great hub.

  • profile image

    Dorrene R 

    10 years ago

    Thanks for the information. This is very helpful.

  • aidenofthetower profile imageAUTHOR


    10 years ago


    You are not alone in wondering that. However, the benefits of fish oil supplements are definitely there and if you don't have a reason you shouldn't take them and you don't get carried away with how much you take there is no reason you shouldn't take them. Plus eating more salmon and other cold water fish can lead to heavy metals poisoning because of pollution in the waters.

  • Patti Ann profile image

    Patti Ann 

    10 years ago from Florida

    I take fish oil supplements because I read about all of the benefits, but now I wonder if it would be better to just eat more salmon and sardines instead. Great hub - thanks for the info!!

  • prasetio30 profile image


    10 years ago from malang-indonesia

    great topic. I like it. thanks for share

  • lefseriver profile image

    David Walli 

    11 years ago from Northern Minnesota

    Dr. Mark Hyman, author of The Ultramind Solution say if you don't like the fishy burp, try freezing the pills; they will digest lower in the GI tract and no burps. Haven't tried it. Thanks for the hub.

  • aidenofthetower profile imageAUTHOR


    11 years ago

    Cinny: If your fish oil is just fish oil then you are just fine. What you need to check is that it isn't made from any fish liver. Those products made from fish liver oil will have a mark, stamp, or claim on their bottle because they are a more concentrated form of omega 3 and 6, but they also contain vitamins A and D. If your product is free of that then you are in the clear!

  • profile image


    11 years ago

    Are all fish oil products also a source of Vit A? The product I take doesn't mention A. I don't want to be double dosing on A (from fish oil) if I'm taking it in addition to fish oil (as a source of Omega 3 & 6)

  • profile image


    11 years ago

    The eye doctor of my mother before give her the fish oil supplement cause according to the doc. it was rich in omega 3. Thanks for the info. of this hub.

  • profile image


    11 years ago

    This is a very detailed and jammed packed with good information. I also take fish oil supplements because it really does heal skin problems from the inside out, I have noticed softer smoother skin on my hands and face. Great hub. :-)

  • frogdropping profile image


    11 years ago

    Aiden - thanks for this. I take cod liver oil, capsule form. As a child it was straight from the spoon - I never liked the taste.

    Interesting to know there's a limit too, and that it's better to take fish oils with food.

    Rated up :)


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