Fish Oil for Companion Pets: Reaching optimal health while balancing environmental sustainability

If we say, “fish oil for dogs or cats,” what is your response? We bet it’s “shiny, beautiful, lush dog coats.” Actually, there’s more to fish oil than just what you see on the surface. For instance, it has positive immune-modulating effects, improves cognition, supports kidney health, promotes a healthy nervous system, and aids in the treatment or prevention of arthritis. Why is that? Fish oil is rich source of the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). 

For all of the positive health benefits of fish oils, however, we need to remember the pitfalls associated with fish and fish oils. For example, the ratio of omega-3 to omega-6 fish oils in pets should be 9:1 and not 4-5:1 as in people, as omega-6 oil can be inflammatory for pets. Further, omega-9 oil is not required for pets. We will help you navigate the information to achieve optimal results for your companion dog.

The top two concerns are: the environment and mercury. 

Environment – Fish oil is not an environmentally sustainable option today. Researchers are actively looking for plant-based options for pets and people or for combinations with fish oil to reduce the amount of fish-dependent oils. 

This can generate confusion. For instance, using flaxseed oil has been explored, which has high levels of another omega-3 fatty acid, alpha-linolenic acid (ALA). Ruminant animals – like cows, goats and sheep – can convert ALA into EPA and DHA. Humans, dogs, and cats are not ruminants. So, they lack the enzymes and efficiency to convert all ALA to EPA and DHA. 

Mercury – Mercury creates an environmental issue, as it naturally occurs at low levels in rocks, soil and water. Throughout the years, human activities have increased the levels of mercury in the atmosphere which drops or is dumped into the ocean – which is then converted there by bacteria into the more toxic methylmercury – to untenable levels. The methylmercury is then absorbed by algae…which are then eaten by zooplankton…which are eaten by small fish…then eaten by bigger fish…then eaten and by even bigger fish…and eventually builds up to toxic levels in large predatory fish…. 

But, fish oil has nondetectable or negligible amounts of mercury and is generally considered safe for humans. However, most companion pets are much smaller.  

So, how do we balance optimal health, avoid toxicity, and lessen our burden on the environment?

For pets, krill (an ancient crustacean), anchovies, and salmon are popular choices for fish oil. We prefer the first two because they are small and therefore have less methylmercury stored in their bodies. Salmon is also considered low in mercury, but is higher in fat and is not an environmentally sustainable option. Additionally, if your companion pet has a food sensitivity or intolerance to salmon or any white-colored fish, we recommend avoiding them altogether. Fortunately, you have the other two options, plus plant-based oils like sunflower, moringa, and borage oils, and even extra virgin olive oil. 

Sounds like winners, right? We clearly need to remember the environment and to make sure we are giving the correct amounts of the right oils to our dogs or cats. 

Yes; there are side effects of too much of these oils, such as: stomach upset; pancreatitis; abnormal bleeding; bruising; or, heavy metal toxicity characterized by appetite loss, incoordination, or seizures.

Now, if you have a bottle of fish oil for your companion pet, you more than likely have the convenient pump, which simplifies adding fish oil to your companion pet’s food and creates less mess. 

Is that one or two pumps of fish oil too much, or possibly too little, for your companion pet? 

The recommended dose of fish oil is 75-100 mg/kg body weight total EPA/DHA acids for companion dogs, according to the non-profit, Canine Arthritis Resources and Education (CARE). The organization provides an excellent chart to figure out how much your companion dog might need based on his weight. 

Remember to also look at the levels (milligrams) of omega-3 fatty acids on the bottle’s label and how much is present according to the guaranteed analysis. This could be in tablespoons or teaspoons. 

Are you wondering about how to give such an exact amount of fish oil to your companion dog? Grab a millimeter syringe (pipette). You can find these at drugstores or online. 

We looked up two fish oil manufacturers for dogs to show you conversion samples.

Manufacturer #1

Total Omega-3 Fatty Acids: 1,285 mg / teaspoon

EPA: 600 mg / teaspoon

DHA: 460 mg / teaspoon

EPA+DHA = 1,060 mg / teaspoon

1 teaspoon = 5 milliliters (approximately) 

1,060 divided by 5 equals 212 mg/ml

Let’s say you have a 5-pound dog. According to CARE’s chart, your dog needs a minimum of 230 mg, but the maximum is 574 mg per day. So, you can give your dog 1.1 milliliters safely or .9 milliliters at 233.2 mg/milliliters.

Manufacturer #2

4,600 mg / teaspoon

Total Omega-3 Fatty Acids: 1,426 mg / teaspoon

EPA: 782 mg / teaspoon

DHA: 460 mg / teaspoon

EPA+DHA = 1,242 mg / teaspoon

1 teaspoon = 5 milliliters (approximately) 

1,242 divided by 5 equals 248.4 mg/ml

Again, let’s say you have a 5-pound dog. One milliliter exceeds the recommended amount, but is quite shy of the maximum. You can give 1 milliliter safely or switch it every other day with .9 milliliters at 223.56 milliliters for an average of 236 mg of EPA and DHA. 


Becker, Karen. “From Anxiety to Arthritis, This Fast-Growing Pet Supplement Is a Godsend.” Healthy Pets, Mercola, 10 Feb. 2019,

Bobeck, Elizabeth Ann. “Nutrition and Health: Companion Animal Applications: Functional Nutrition in Livestock and Companion Animals to Modulate the Immune Response.” Journal of Animal Science, vol. 98, no. 3, 2020,

Burron, Scarlett, et al. “Safety of Dietary Camelina Oil Supplementation in Healthy, Adult Dogs.” Animals, vol. 11, no. 9, 5 Sept. 2021,

Dodds, W. Jean. “Revealing Adulterated Pet Food.” Hemopet, 18 June 2021,

Dominguez, Tonje E., et al. “Enhanced Omega‐3 Index after Long‐ versus Short‐Chain Omega‐3 Fatty Acid Supplementation in Dogs.” Veterinary Medicine and Science, vol. 7, no. 2, 2020, pp. 370–377,

Foran, Stacy E., et al. “Measurement of Mercury Levels in Concentrated over-the-Counter Fish Oil Preparations: Is Fish Oil Healthier than Fish?” Archives of Pathology & Laboratory Medicine, vol. 127, no. 12, 2003, pp. 1603–1605,

Scroll to Top