Fish Oil For Dogs

Fish Oil For Dogs

Fish oil is a controversial and often confusing topic. Veterinarians recommend it and many dog owners swear by it. But then you read headlines like “I almost killed my dog with fish oil” … so you don’t know what to believe.

RELATED: Can dogs eat fish? …

Is Fish Oil Good For Dogs?

The answer is … fish oil is both good and bad. It’s one of the most popular ways to give your dog omega-3 fatty acids … and omega-3s for dogs have tons of health benefits. But fish oil comes with some negatives as well.

Here’s a detailed look at the benefits and disadvantages of fish oil.

Benefits Of Fish Oil For Dogs

Fish oil can be an important source of omega-3 fatty acids. And your dog needs omega-3s to balance out the omega-6 fatty acids in his diet.

Balance Omega-6 and Omega-3 Fatty Acids

Omega-6 is usually too high in dogs’ diets. Most dogs eat meat or processed foods that supply too much omega-6. Too much omega-6 can cause chronic inflammation in your dog. And that can lead to diseases like …

  • Allergies
  • Arthritis
  • Autoimmune diseases
  • Diabetes
  • Cancer

So it’s important to give your dog omega-3 fatty acids to lower the risk of these chronic illnesses. And fish oil can provide some important ones.

EPA And DHA: Essential Fatty Acids In Fish Oil
Fish oil provides your dog with the essential omega-3 fatty acids EPA and DHA. They’re considered essential because they need to come from your dog’s diet.

Your dog’s body can actually make EPA and DHA. But it’s quite an inefficient process. It doesn’t provide your dog with much EPA and DHA. So you need to make sure he gets them in his diet.

Benefits of EPA and DHA
EPA and DHA are powerful additions to your dog’s diet. EPA has anti-inflammatory effects and supports your dog’s immune response. DHA is vital for eye, brain and nervous system health.

Here are some of the known benefits of EPA and DHA …

  • Support brain health
  • Promote nervous system development
  • Fight inflammation
  • Lower heart disease risks
  • Maintain eye health
  • Promote brain and eye development in puppies
  • Support healthy skin and coat, relieve allergies
  • Improve joint health
  • May decrease the risk of some cancers 
  • Reduce metabolic endotoxemia in the gut
  • Work with probiotics to boost beneficial bifidobacteria in the gut

What Happens If Your Dog Is Deficient In EPA or DHA?
Lack of EPA can cause depression in animals. Lack of DHA is linked to cognitive issues. Other signs of omega-3 deficiencies can be …

  • Dull or poor coat
  • Dry or flaky skin
  • Allergies
  • Slow wound healing
  • Ear infections
  • Hot spots

It’s clear your dog definitely needs omega-3 fatty acids in his diet. So then the next question on your mind is probably …

What’s The Best Fish Oil For Dogs?

Unfortunately, that’s another question without a simple answer. Before you try to find the best fish oil for your dog, you need to read about its drawbacks … and some alternatives.

Why Is Fish Oil Bad For Dogs?

There are some very good reasons not to use fish oil. The first one is …

1. Fish Oil Is Missing Important Anti-Inflammatory Fats

There are some other important anti-inflammatory fats … but they aren’t in fish oil.

ETA (eicosatetraenoic acid) is another omega-3 anti-inflammatory fatty acid. It can also help regenerate cartilage in a dog with arthritis. Your dog can convert ETA to EPA … but not the other way around. So if there’s no ETA in his diet, he’s missing out.

GLA (gamma-linolenic acid) is an omega-6 fatty acid that has anti-inflammatory benefits. It helps with hormone balance and supports your dog’s coat and skin. But GLA only comes from plants. Fish oil doesn’t have it.

RELATED: Inflammation can shorten your dog’s life …

2. Fish Oil Can Be Toxic

Sadly our oceans are full of contaminants. And the fish that live there are too. And guess where toxins are stored in fish bodies. Yes, in the fat … that becomes your dog’s fish oil. So fish oil could be harming your dog with these poisons.


Fish skin accumulates toxins. Your dog may love crunchy fish skin treats, but it’s best to avoid them.

Fish these days are polluted with dangerous heavy metals … like arsenic, lead, mercury and cadmium. These toxins may be in your fish oil, and they can cause …

  • Cancers
  • Organ damage (liver, kidneys)
  • Endocrine issues
  • Blindness
  • Neurological problems
  • Leaky gut and yeast
  • Immune problems

Other toxins in fish include …

Polychlorinated Biphenyls (PCBs)
These industrial chemicals can increase cancer risk. They can harm unborn infants and may cause learning disabilities. Fatty fish are especially prone to carry these toxins. Farmed salmon that are fed ground-up fish are higher in PCBs. And farmed salmon are a big source of fish oil.

Dioxins And Furans
Dioxins and furans are common environmental pollutants. They’re on the “dirty dozen” list of persistent organic pollutants (POPs).

Most dioxin and furan exposure is from contaminated food. They accumulate in fatty tissues. They cause reproductive and developmental problems. Dioxins and furans harm the immune system, disrupt hormones and cause cancer. They last a long time in the body … and they’re high in Great Lakes fish.

If you buy a really good quality fish oil, they should be free of these pollutants. But just to make sure, ask the manufacturer for a Certificate of Analysis (COA).

3. Fish Oil Is Radioactive

If you give your dog fish oil from Pacific fish, beware. The Fukushima nuclear power plant disaster released radioactive water into the Pacific Ocean.

In a 2013 Stanford University study, Pacific fish tested positive for radioactive particles. Tuna was especially toxic, but salmon used to make fish oil has also tested positive. Radioactive substances like Cesium and Strontium can get into your dog’s bone marrow. That can lead to bone cancer and leukemia.

4. Fish Oil Goes Rancid

Fish oil is extremely unstable. That means it oxidizes (turns rancid) very easily … as soon as it’s exposed to air. If you ever take the cap off a bottle of fish oil and it smells fishy … don’t use it. Good fish oil shouldn’t smell bad.

This isn’t just an odor problem. Oxidation produces unstable molecules called free radicals. When free radicals build up, they can harm your dog’s cells, proteins and DNA. This is known as oxidative stress. It can lead to premature aging and chronic disease, including …

  • Joint disease
  • Heart, liver or kidney disease
  • Cognitive decline
  • Cancer

And it’s really hard to stop fish oil from oxidizing. Sometimes it’s rancid before you open the bottle. Air can even get into the fish oil through plastic containers. So always buy your fish oil in dark glass bottles or jars … and refrigerate it. If you buy gel caps, you can store them in the freezer and they’ll last longer.

5. Fish Oil Harms Ocean Environments

Your dog’s fish oil is depleting the oceans. Industrial fishing practices have collateral damage. Suction fishing techniques vacuum up other fish. And mammals like whales, porpoises and dolphins get caught in fishing nets.

Fish used for fish oil include vast amounts of menhaden fish. Menhaden fish eat algae blooms and keep the oceans clean and support other aquatic life.

Other fish being destroyed by the fish oil industry are Peruvian anchovies. Fish oil manufacturers are using as much as 10 million metric tons a year! That’s about an eighth of all the fish caught in the world. 

Krill oil is an environmental problem too. Whales and other mammals rely on krill to survive. And krill are endangered due to over-fishing as well as climate change. This is happening despite many sellers who claim their products are sustainably caught. Read more about why krill oil is an irresponsible choice

Calamari (squid) oil is in growing demand. Squids’ short life cycle may mean they contain less toxins than other fish oils. That shorter life cycle also means that squid are not currently endangered. But that can change fast because squid and their eggs have so many predators

As other sources of food disappear, squid and their eggs are easy prey for whales, sharks, many other fish and even birds. Because so many fish eat squid, fishermen use squid as bait too! And we humans eat millions of pounds of squid each year when we enjoy calamari dishes. Research shows that squid are an important part of the ocean food chain …. and “large removals of squids will likely have large-scale effects on marine ecosystems.” So the claim that squid oil is sustainable isn’t accurate.

6. Fish Oil Has Unexpected Side Effects

While fish oil can offer great health benefits for your dog, there can be some risks too. These are often due to too much EPA in the diet. And that can happen with high fish oil doses, so don’t overdo the amount you give your dog.

High Blood Sugar
Be careful with fish oil if your dog’s diabetic. Omega-3 fatty acids are often said to support healthy blood sugar levels. But there’s now research showing high doses can increase blood glucose.

Fish oil can thin the blood and can cause bleeding. Some people experience bleeding gums or nosebleeds. It may interact with medications like blood thinners. This bleeding risk also means increased risk of hemorrhagic stroke. And if you give fish oil, stop dosing a few days before any surgery.

Low Blood Pressure
Fish oil’s well known to lower blood pressure. And that can be a good thing if your dog has high blood pressure. But not if your dog’s pressure is normal! And it can increase the effects of blood pressure medication too.

Some dogs don’t tolerate fish oil well, especially at high doses. It could cause diarrhea or other digestive upset in your dog. If this happens, you’ll want to find an alternative source of omega-3s. 

Heart Health
Omega-3 supplements are usually touted as heart-healthy. But researchers recently looked at 5 other clinical studies … with surprising results. Heart patients receiving fish oil supplements experienced higher incidence of atrial fibrillation (abnormal heart rhythm). 

These contradictions are puzzling because other studies claim omega-3 fatty acids help with most heart issues. The difference seems to be whether the patients get their omega-3s from food or supplements. So if your dog has heart problems, it’s safest to feed fish instead of giving fish oil supplements. Or use a non-fish oil source of omega-3s. 

Acid Reflux
If you’ve taken fish oil yourself, you may be familiar with those “fishy burps.” That’s your digestive system telling you it doesn’t like fish oil. And your dog can experience that problem too. If you notice your dog burping, licking his lips or looking uncomfortable after fish oil, it could be causing acid reflux or indigestion.

Vitamin A Toxicity
It’s safest not to give your dog cod liver oil. It’s high in vitamin A which can be toxic in larger amounts. Keep the bottle out of your dog’s reach so he doesn’t get into it by mistake, and always use specific dosing for dogs.

So, it’s pretty easy to see that the negatives of fish oil outweigh the positives. Luckily there are a lot of better alternatives.

The Best Omega-3 For Dogs

There are many ways to give your dog the benefits of fish oil without the risks. So what’s the best omega-3 for dogs?

Green Lipped Mussel Oil

Green lipped mussels are native to clean New Zealand waters. This oil has several advantages over fish oil.

Green lipped mussel oil contains 30 fatty acids … compared to other marine oils which have only two. It’s rich in EPA and DHA, like fish oil. But it beats fish oil because of its ETA content, something fish oil lacks.

ETA is an omega-3 fat that controls inflammation in your dog. But it also works indirectly to manage inflammation and pain. That’s because ETA lowers the body’s release of the omega-6 fatty acid ARA – arachidonic acid. ARA creates prostaglandins that drive your dog’s pain and inflammation response. So limiting ARA to manage prostaglandins helps control pain and inflammation.

ETA in green lipped mussels will also help your dog avoid the side effects of too much EPA from fish oil. ETA is a precursor to EPA, … so your dog’s body will only make as much EPA as it needs.

Green lipped mussels also contain phophospholipids, which makes it more bioavailable than fish oil. A 1997 study by researchers at the University of Queensland found that its bioavailability makes green lipped mussel extract 247 times more potent than salmon oil.

Green lipped mussels are also sustainably farmed, making them an environmentally responsible choice. Instead of feeding on corn and soy like other farmed fish … green lipped mussels eat phytoplankton, which can also be sustainably grown.

Ahiflower Oil

Ahiflower oil is new to the omega scene … and it offers a wealth of benefits. It’s a plant whose seeds deliver high amounts of SDA (stearidonic acid). SDA’s important as a precursor to ETA and EPA, so it helps the body produce these fatty acids. Ahiflower oil also contains the essential omega-6 fat, GLA (60% more than hempseed oil). And as a plant oil, ahiflower is a fully sustainable source of oil.

Algal Oil

Algal oil is a good source of DHA, but it only has a small amount of EPA, and, like fish oil, no GLA or ETA. As a plant-derived oil, it’s popular with vegetarians who want some omega-3s in their diet. It’s a sustainable oil. So much so, that studies suggest it’s a good source of biodiesel, as a petroleum alternative!

Hempseed Oil

Hempseed oil is another good plant oil. But don’t confuse hempseed oil with CBD oil that’s made from hemp plants. Hempseed is a great nutritional oil that provides a perfect balance of omega-3, 6 and 9 fatty acids. Unlike fish oil, it contains the important anti-inflammatory omega-6 fat, GLA. And it also has SDA, the precursor to EPA (but only 1/10 the amount of SDA in ahiflower oil).

So … you can see there are other ways to give your dog the health benefits of fish oil … and even improve on them by adding some plant oils. You don’t need to raid the oceans or expose your dog to toxins.


Kaliannan K et al. A host-microbiome interaction mediates the opposing effects of omega-6 and omega-3 fatty acids on metabolic endotoxemia. Sci Rep. 2015 Jun 11;5:11276.

Abba C et al. Essential fatty acids supplementation in different-stage atopic dogs fed on a controlled diet. Anim Physiol Anim Nutr (Berl). 2005 Apr-Jun;89(3-6):203-7. 

TD Watson. Diet and skin disease in dogs and cats. J Nutr. 1998 Dec;128(12 Suppl):2783S-2789S. 

Freeman LM. Beneficial effects of omega-3 fatty acids in cardiovascular disease. J Small Anim Pract. 2010 Sep;51(9):462-70.

Lenox CE et al. Potential adverse effects of omega‐3 fatty acids in dogs and cats. J Vet Intern Med. 2013 Mar-Apr;27(2):217-226.

Gandhi N et al. Dioxins in great lakes fish: Past, present and implications for future monitoring. Chemosphere. 2019 May;222:479-488. 

Pye C, Crews C. Furan in canned sardines and other fish. Food Addit Contam Part B Surveill. 2014;7(1):43-5. 

Friday KE et al. Elevated plasma glucose and lowered triglyceride levels from omega-3 fatty acid supplementation in type II diabetes. Diabetes Care. 1989 Apr;12(4):276-81. 

McEwen BJ et al. Effects of omega-3 polyunsaturated fatty acids on platelet function in healthy subjects and subjects with cardiovascular disease. Semin Thromb Hemost. 2013 Feb;39(1):25-32.

Morris MC, Sacks F, Rosner B. Does fish oil lower blood pressure? A meta-analysis of controlled trials. Circulation. 1993 Aug;88(2):523-33.

Afsoon Emami Nainin et al. Effect of Omega-3 fatty acids on blood pressure and serum lipids in continuous ambulatory peritoneal dialysis patients. J. Res Pharm Pract. 2015 Jul-Sep:4(3):135-141

Bradberry, JC et al. Overview of omega-3 fatty acid therapies. P.T. 2013 Nov;38(11):581-691.

Michaela C. Pascoe et al. Fish oil diet associated with acute reperfusion related hemorrhage, and with reduced stroke-related sickness behaviors and motor impairment. Front Neurol. 2014:5:14.

Marta Col et al. Assessing the trophic position and ecological role of squids in marine ecosystems by means of food-web models. Deep Sea Research Part II: Topical Studies in Oceanography, Volume 95, 2013, Pages 21-36,
ISSN 0967-0645.

Whitehouse MW, Macrides TA, Kalafatis N, Betts WH, Haynes DR, Broadbent J. Anti-inflammatory activity of a lipid fraction (lyprinol) from the NZ green-lipped mussel. Inflammophrmacology. 1997;5(3):237-46. 

5 minutes a day. Healthier Dog.

Get important health plans from vets & experts. It’s natural and it’s free.


Get instant access to easy-to-make and affordable recipes. Plus get new recipes delivered right to your inbox.

Recipe Cards for Making Raw Dog Food

Related Posts