It’s not difficult to avoid a fish oil overdose in dogs and cats, but take a moment to educate yourself about appropriate dosages. If you’re like most pet owners, you’re a bit confused by the terminology and how to safely use these supplements. I’m going to try to answer all the questions I’ve heard on the topic here!

How much is too much fish oil? Unless your dog or cat is under the care of a veterinarian, limit her dose to no more than 1/4 teaspoon of fish oil per 10 pounds of body weight. I recommend Nordic Naturals Omega-3 Pet products. You can follow the dosing directions on the label for your dog and cat.

Fish oil supplements are generally safe when used as directed but too much can cause serious problems, including:

  • Abnormal platelet function
  • Gastrointestinal symptoms
  • Decreased wound healing
  • Damage to lipids (fats) in cells of the body
  • Oversupply of nutrients and potential toxin exposure
  • Weight gain
  • Changes in immune system function
  • Changes in blood sugar regulation
  • Alteration of drug metabolism

What Are Essential Fatty Acids?

Dogs and cats have a physiological requirement for certain fats in their diet to survive. These are called essential fatty acids (EFA’s), meaning the animal can’t manufacture these compounds in adequate amounts from other materials. EFA’s must come from their diet.

Dogs and cats have five EFA’s they must obtain from food (NRC, 2006):

  • Linoleic acid (LA, omega–6)
  • Alpha-linolenic acid (ALA, omega–3)
  • Arachidonic acid (AA, omega–6)
  • Eicosapentaenoic acid (EPA, omega–3)
  • Docosahexaenoic acid (DHA, omega–3)

The term “omega” is a description of the fatty acid’s structure and not really necessary to understand for this discussion. You just need to understand that omega–6’s are different from omega–3’s but they’re both important.

Pet’s bodies work best when they consume a particular ratio of omega–6 to omega–3. An excess of either one can cause health problems.

Scientists believe an optimum ratio is somewhere between 10:1 and 5:1 (omega–6 to omega–3). It’s important to remember that the omega–3 fatty acid ALA is less metabolically available to dogs and not available at all to cats. So even if a food has a good ratio of fats, if the omega–3’s are in the form of ALA, the fat balance is not ideal.

Different Omegas Have Different Functions in the Body

Omega–6 fatty acids come from grains, vegetable oils, nuts, seeds, poultry, and eggs. Omega–6 fatty acids promote inflammation, which sounds bad, but inflammation is necessary for healing the body. Pets need omega–6 to be able to heal properly. But when there’s an excess in omega–6, there will be excess inflammation.

Omega–3 fatty acids have an anti-inflammatory effect in your dog’s or cat’s body. They are found in high concentrations in fish and in lesser amounts in nuts and seeds. Dogs and cats need to consume enough omega–3 fatty acids to balance out the omega–6 fatty acids that are abundant in their regular diet. One of the easiest ways to get more omega–3 fatty acids into your pet is to use a fish oil supplement.

Why Pets Need Extra Omega-3s

The modern pet’s diet provides higher levels of omega–6 than omega 3. This is partly because dog and cat foods contain grains, vegetable oils, and poultry products. The other part of the reason is that omega–3’s are fragile and can become oxidized under typical pet food storage conditions. Oxidized fats are not helpful to pets.

Pet food may have adequate omega–3 levels when it’s made, but after being stored in questionable conditions for a year the levels can drop significantly. This drop can lead to an imbalance between omega–6 and omega–3 at the time of feeding.

Avoid a Dog Fish Oil Overdose (Cats, too)

Benefits of Higher Omega–3 Intake

Omega–3 added to your pet’s diet can decrease unwanted inflammation. Scientific research supports the use of omega–3 supplements for several canine and feline diseases, including

  • Osteoarthritis in dogs (Fritsch, Allen, Dodd, Jewell, Sixby, Leventhal, & Hahn, 2010) and cats (Lascelles, DePuy, & Hansen, 2010)
  • Skin allergy symptoms in dogs (Harvey, 1999)
  • Aging changes in dogs (Hall & Jewell, 2012)
  • Renal disease in cats (Plantinga, Everts, & Kastelein, 2005)
  • Obesity in cats (Wilkins & Waldron, 2004)
  • Aggression in dogs (Re, Zanoletti, & Emanuele 2008)

Fixing Fat Balance Through Diet Modifications

Even though this is an article about fish oil supplementation, I want to make an argument for using whole foods instead of supplements to improve your pet’s fatty acid balance. Whole foods have nutrients in their natural state and may confer even greater benefits than refined supplements.

There are two approaches to balancing the omega–6: omega–3 ratio. I suggest doing a bit of both:

  1. Increase consumption of foods high in omega–3 and low in omega–6.
  2. Decrease consumption of foods high in omega–6 and low in omega–3.

Increase Omega–3 Intake

You can consult this list of foods with lower omega–6: omega–3 ratios.

Cold-water, oily fish are high in omega–3 and low in omega–6.

Canned salmon and water-packed canned sardines are convenient and affordable options. They are whole foods with a lot of omega–3 fatty acids.

  • 3 ounces of canned pink salmon (with skin and bones) contains about 718 mg of EPA and 685 mg of DHA (a total of 1403 mg of omega–3).
  • 3.2 ounces of canned sardines contain 430 mg of EPA and 460 mg of DHA (a total of 890 mg of omega–3).

A 10-pound dog or cat could benefit from eating half an ounce of salmon or sardines even a few times a month. Start with small quantities given infrequently to allow your pet’s digestive tract to get used to them.

Other foods containing EPA and DHA are beef, lamb, and poultry liver and omega–3 enriched eggs (USDA, 2005). These sources have less omega–3 than fish but are still worth considering.

Reduce Omega–6 Intake

The second strategy for fixing fat imbalance is to reduce the consumption of omega–6 fats. Omega–6 fats are prevalent in poultry, seeds, seed oils like corn, soybean, and canola oils that are prevalent in commercial pet food.

Moving away from chicken- or turkey-based dry pet food can be an effective strategy to reduce omega–6 intake. That’s not to say you can never feed poultry, but feeding only poultry as a protein source every day may overload your pet with omega–6 compared to omega–3.

Fish-based kibble is less likely to have excess omega–6, but buy the smallest, freshest bag you can find and store it in the refrigerator. Fat from fish is delicate and can go rancid quickly. Rancid fish oil is not going to do your pet any favors.

Another good option to consider is replacing a couple of kibble meals each week with fresh grass-fed beef or fish recipes. Fresh foods contain fresh fats. Fresh fats are more effective as anti-inflammatories.

Avoid a Dog Fish Oil Overdose (Cats, Too)

Fixing Fat Balance With Omega–3 Supplement

With chicken-based dry dog food being so cheap and easy to find, the reality is most pet owners will continue to buy it. For those of you who make this choice, the addition of fish oil will help offset the excess omega–6 in the average dog food.

Salmon oil, krill oil, cod liver oil, flaxseed oil, hemp seeds, chia seeds… All have omega–3 but they’re not all equal. What’s the difference?

Salmon and krill oil are similar to regular fish oil and may contain an even higher concentration of EPA+DHA. These are both good options but may be more expensive and less environmentally friendly.

Cod liver oil is not the same as fish oil because it contains significant quantities of vitamins A and D. Pets can overdose on these vitamins if you give them too much cod liver oil. My advice is to stay away from cod liver oil unless you’re working with a veterinarian who prescribes it for a specific condition.

Flaxseed oil, hemp oil, hemp seeds, chia seeds, etc. are plant-based sources of omega–3 that may be beneficial in some cases. But they are not the same thing as fish oil and shouldn’t be used as a replacement for fish or fish oil. Dogs don’t absorb the omega–3 fatty acid ALA present in plant-based foods as well as the EPA and DHA from fish oil.

One notable exception to this is algae oil. Algae oil is a plant-sourced product that contains EPA and DHA, but there is little information about its safety or efficacy when fed to dogs and cats.

What is Fish Oil?

Fish oil is a nutritional supplement made by extracting and purifying the fat from oily fish. Sardines, herring, mackerel, anchovies, and salmon are used to make fish oil. High-quality fish oil is a fresh, concentrated source of omega–3 fatty acids. It contains the two key omega–3’s dogs and cats need–eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

Fish oil is available in liquid, capsule or tablet form. You’ll find many different products at pet supply, grocery, and online stores. But not every fish oil product is worth buying.

How to Choose a Good Fish Oil for Your Dog or Cat

One way to make sure a product has been adequately tested for purity is to look for an IFOS rating/logo on the label. The “International Fish Oil Standards Program” or IFOS is an independent group that tests and certifies fish oils.

IFOS has a website that lists the fish oil products they’ve certified. The IFOS certification verifies a product’s purity, potency, and freshness.

Here’s a news flash: fish oil does not necessarily smell horribly fishy. If yours does, it may be rancid and should not be used.

I’ve found the higher quality products like Nordic Naturals and Carlson’s don’t have a strong fishy odor. Buy only the amount of fish oil you’ll use in a month and store it in the refrigerator to keep it fresh longer.

Read the Label to Find EPA+DHA in Milligrams

Fish oil supplements bear a label that lists both the total amount omega–3 and the amount of EPA and DHA the product contains. The number you’re looking for is the sum of the EPA and DHA in milligrams (mg). Each product has different amounts, so you must check the label to determine the right amount to give your pet. Also, check for the “IFOS” logo as well as the product expiration date.

Cat and Dog Fish Oil Overdose Side Effects

The judicious use of fish oil for dogs and cats seems to be well-tolerated by most animals and can help improve some disease conditions. However, more is not always better. The overuse of fish oil can cause serious harm to your pet.

According to a paper published in the Journal of Veterinary Internal Medicine (Lenox, Bauer, 2013), cat and dog fish oil overdoses can cause:

  • Abnormal platelet function
  • Gastrointestinal symptoms
  • Decreased wound healing
  • Damage to lipids (fats) in cells of the body
  • Oversupply of nutrients and potential toxin exposure
  • Weight gain
  • Changes in immune system function
  • Changes in blood sugar regulation
  • Alteration of drug metabolism

Before you pour a glug or two of fish oil onto your pet’s food, take a few minutes to learn more about how to use this supplement safely.

How Much Fish Oil Should You Give Your Dog or Cat?

The perfect amount of omega–3 fatty acids for dogs and cats is not known. Super-high doses have been used to treat severe inflammatory disease, but for creating an everyday healthy balance of omega–6 to omega–3, the dose is much lower.

The National Research Council (NRC) is an organization of scientists who provide guidelines on the nutritional requirements of dogs and cats. The NRC recommended allowance is only 30 mg EPA+DHA per metabolic body weight for dogs and 2.5 mg EPA+DHA per metabolic body weight for cats. The calculation cannot be done on a per pound basis.

For that reason, I’ve included a table below so you can get a close estimate of how much EPA+DHA your dog or cat should get daily while avoiding a cat or dog fish oil overdose. Keep in mind that most commercial pet food products already contain an adequate amount of omega–3 fatty acids when manufactured.

Adding a small amount of fish oil as a supplement will compensate in situations where the fats in pet food might not be fresh. It will also help balance things out for pets who get a significant amount of treats that contain lots of omega–6 and no omega–3.

These dosages are much lower than what you’ll find in other places on the internet. These are nutritional doses, not anti-inflammatory doses.

Although much higher doses have been recommended for pets with certain diseases, more is not always better. As noted earlier, excess dietary omega–3’s can cause very serious illness in pets. Unless you are working under the direction of a veterinarian, stick with the nutritional doses outlined here for healthy pets.

Remember to use the sum of EPA+DHA in milligrams (not the milligrams of “total omega–3’s”) to calculate the dose.

Fish Oil Daily Dosage Chart for Healthy Dogs and Cats (NRC, 2006)

Body Weight in PoundsEPA+DHA in mg for DogsEPA+DHA in mg for Cats
5555
10937
121078
151279
2015711
30213 
40264 
50312 
60358 
70402 
80444 
90485 
100525 

If your pet has a disease associated with inflammation, higher doses of omega-3 will be necessary to see improvement. The following table lists anti-inflammatory doses of fish oil for dogs and cats. There is no need to give doses this high to healthy dogs and cats. Please check with your veterinarian before starting your pet on a therapeutic dosage of fish oil. 

Fish Oil Daily Dosage Chart for Inflammatory Conditions in Dogs and Cats (Bauer, 2011)

Body Weight in PoundsEPA+DHA in mg for DogsEPA+DHA in mg for Cats*
5230121
10390193
12450218
15530253
20650307
30890 
401100 
501300 
601500 
701675 
801850 
902020 
1002190 

*Little information is available about fish oil supplementation in cats. This dosage is toward the high end of what Bauer considers “safe.” Do not exceed this dose unless directed by a veterinarian.

Use caution when giving any oil or fat to animals who are prone to bouts of pancreatitis.

If your pet has a sensitive stomach, start with 50% of the dose from the table for two weeks and stop if you notice diarrhea or an upset stomach. A high-quality, fresh, refrigerated product will help minimize potential side-effects.

Vet-Recommended Fish Oil Supplements

For simplicity’s sake, you can opt to buy fish oil made specifically for pets. One such product is Nordic Naturals Omega-3 Pet.

It’s available as capsules or liquid and doesn’t have any flavoring. Although many of their products have no IFOS rating, you can find extensive safety testing information on the company’s website for each batch of fish oil they produce.

The label-recommended dosage on Nordic Naturals Omega-3 Pet products is somewhere between an anti-inflammatory and nutritional dosage. Most dogs and cats should be able to tolerate this moderate dosage, but it’s still a good idea to introduce it gradually.

To avoid the stress of pill administration, buy the liquid form and mix it with your pet’s food. Most dogs like the taste and cats will accept a small amount of high-quality fish oil mixed with canned food.

Nordic Naturals Omega-3 Pet products are high-quality and inspected to ensure purity. It’s even available in a 2-ounce container for small dogs and cats so it won’t go rancid before you use it all.

Please remember, just like with food, it’s a good idea to rotate your brands of fish oil (or salmon oil, or krill oil). Don’t use the same one for years on end! If there are weaknesses in the product you’re using, they will eventually show up in your pet. By using different brands, it’s less likely your pet will be a victim of excesses or deficiencies in one particular product.

Products to Avoid

  • Oils with vitamin D or other compounds added. Unless you’re trying to add vitamin D to your pet’s diet on purpose, you should avoid fish oil with vitamin D added. You may find that even high-quality products contain ingredients like d-alpha-tocopherol and/or rosemary extract to protect delicate fatty acids. If you wish to avoid rosemary extract, the Nordic Naturals Omega-3 Pet line does not contain it.
  • “Burpless” capsules. Your pets don’t need them and since they’re made for human stomachs, they may not dissolve as intended in a dog’s or cat’s stomach.
  • Cod liver oil. It’s different than regular fish oil and should not be used as a substitute.
  • Plant-source omega–3 supplements. Pets aren’t able to absorb these the way humans can. They’re not a substitute for fish oil.
  • Cheap fish oil capsules in large containers. Buy small containers and store them in the refrigerator! Use up the entire container in a couple of months, or at the latest, by the expiration date on the product label. Discard any product that has a strong fishy odor.

photo credits CC/BY 2.0: Chris Barnes, Anne Worner

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References

Bauer, J. E. (2011). Therapeutic use of fish oils in companion animals. Journal of the American Veterinary Medical Association, 239(11), 1441–1451.

Fritsch, D., Allen, T. A., Dodd, C. E., Jewell, D. E., Sixby, K. A., Leventhal, P. S., & Hahn, K. A. (2010). Dose‐titration effects of fish oil in osteoarthritic dogs. Journal of Veterinary Internal Medicine, 24(5), 1020–1026.

Hall, J. A., & Jewell, D. E. (2012). Feeding healthy beagles medium-chain triglycerides, fish oil, and carnitine offsets age-related changes in serum fatty acids and carnitine metabolites. PLoS One, 7(11), e49510.

Harvey, R. G. (1999). A blinded, placebo-controlled study of the efficacy of borage seed oil and fish oil in the management of canine atopy. The Veterinary Record, 144(15), 405.

Lascelles BDX, DePuy V, Hansen TB, et al. (2010). Evaluation of a therapeutic diet for feline degenerative joint disease. Journal of Veterinary Internal Medicine, 24, 487–495.

Lenox, C. E., & Bauer, J. E. (2013). Potential adverse effects of omega‐3 fatty acids in dogs and cats. Journal of Veterinary Internal Medicine, 27(2), 217–226.

National Research Council (NRC). (2006). Nutrient requirements of dogs and cats. National Academies Press.

Plantinga, E. A., Everts, H., Kastelein, A. M., & Beynen, A. C. (2005). Retrospective study of the survival of cats with acquired chronic renal insufficiency offered different commercial diets. Veterinary Record, 157(7), 185.

Re, S., Zanoletti, M., & Emanuele, E. (2008). Aggressive dogs are characterized by low omega–3 polyunsaturated fatty acid status. Veterinary Research Communications, 32(3), 225–230.

US Department of Agriculture (USDA). (2005). National Nutrient Database for Standard Reference, Release 28.

Wilkins, C., Long Jr, R. C., Waldron, M., Ferguson, D. C., & Hoenig, M. (2004). Assessment of the influence of fatty acids on indices of insulin sensitivity and myocellular lipid content by use of magnetic resonance spectroscopy in cats. American Journal of Veterinary Research, 65(8), 1090–1099.

 

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