Best Fish Oil for Dogs, Priced by the EPA and DHA You Actually Get

Fish oil is the rare dog supplement where the evidence and the shelf point the same way, and the shelf still manages to mislead. Cornell's Riney Canine Health Center quotes Dr. Christopher Frye saying that the supplement with the most support in the literature for joint health is omega-3 fatty acids from fish oil. Dr. Joseph Wakshlag, quoted on the same page, says few joint supplements other than fish oil have been definitively shown to help slow the degeneration.

The trouble is the label. A bottle can lead with total oil, or with total omega-3, or with an "omega 3-6-9" blend, and none of those is the figure that matters. The dose arithmetic for fish oil is worked through in full elsewhere on this site. This guide takes the next step and narrows the aisle to three products that print the useful number, then prices each one by it.

The one number to shop by

Combined EPA and DHA. Today's Veterinary Practice, in a review by board-certified veterinary nutritionists Donna Raditic and Laura Gaylord, describes EPA and DHA as the active ingredient in common pet fish oil supplements. Colorado State University's veterinary hospital puts it more bluntly on its dosing chart: quality products display amounts of EPA and DHA on the label.

So the comparison below ignores the big number on the front. Each product's EPA and DHA per serving comes from the maker's own published analysis, and the price is divided by it to give a cost per 1,000mg of EPA plus DHA. It puts a scoop, a pump and a capsule on the same scale.

What the dose guidance says

CSU's chart sets a maximum of 310mg of EPA and DHA per kilogram of body weight to the power 0.75 per day, for dogs with osteoarthritis. The chart converts that into plain figures: 965mg a day for a 10lb dog, 1,623mg for 20lb, 2,200mg for 30lb and 2,730mg for 40lb. CSU adds two qualifiers that are easy to skip. The maximum is not tolerated by every dog and a lower dose may be preferable, and the page suggests starting near a quarter of the maximum.

The Today's Veterinary Practice review gives a wider therapeutic range of 50 to 220mg per kilogram of body weight, with the highest dose reserved for osteoarthritis. It also cites the National Research Council's safe upper limit for dogs of 280mg of combined EPA and DHA per 100 kcal of diet.

None of this is a dosing instruction, and nothing here should be read as one. Neither writer on this site is a veterinarian. The figures are what CSU and the review state, and the point of printing them is to show how far apart products sit. The right amount for a given dog is a conversation for its vet, particularly for a dog already on pain medication.

Who should not start here

Cornell's page carries a line worth taking seriously before buying anything: Frye says he never recommends this supplement in overweight dogs, and suggests adding fish oil once the dog is at a healthy weight. Fish oil is fat. A dog carrying extra weight gets more from getting the daily calories right than from a pump of oil on top of the same meal.

The review lists the effects to know about at higher doses: altered platelet function, gastrointestinal upset, slower wound healing and weight gain. CSU names loose stools and vomiting as the signs to watch when the amount goes up. A dog facing surgery, a dog with a history of pancreatitis, and a dog on any medication that affects clotting all belong in the vet's office before the bottle comes home.

The three worth buying

How they compare

Fish oil	Serving	EPA + DHA per serving	Price	Per 1,000mg EPA + DHA
Nutramax Welactin liquid, 16 fl oz	6mL scoop	1,330mg	$29.99	About $0.29
Grizzly Salmon Plus, 32 oz	1 teaspoon	966mg	$40.00	About $0.22
Nordic Naturals Omega-3 Pet Soft Gels, 90 count	1 soft gel	255mg	$19.51	About $0.85

The sticker price ranks these backwards. The cheapest bottle on the shelf is the most expensive way to buy EPA and DHA, and the dearest bottle is the cheapest.

Who each one is wrong for

Welactin is wrong for a toy breed. The smallest step on the chart is half a scoop every other day, and a dog under 5lb is off the chart entirely. For a very small dog a capsule with a fixed, smaller amount is easier to get right.

Grizzly is wrong for a one-small-dog household. The maker's 90-day window after opening is the limit that matters, and a dog getting a fraction of a teaspoon a day will leave most of a 32 oz bottle to oxidise. Grizzly sells 4, 8 and 16 oz bottles, and the smaller one is the better buy even at a worse unit price.

Nordic Naturals is wrong for a big dog on a joint plan. At 255mg a capsule, the amounts CSU charts for a 40lb dog run past ten capsules a day. That is a lot of capsules, a lot of gelatin, and a 90-count bottle that empties in nine days or less.

All three are wrong for a dog carrying extra weight. That is Cornell's point, and it costs nothing to follow.

Freshness and the bottle size trap

Oxidised fish oil is the hidden cost in this category. CSU advises looking for a product that evaluates purity and freshness through third-party testing. Grizzly's own page gives at least 20 months unopened and 90 days once opened, and says the oil can sit at room temperature away from sunlight or go in the fridge. The cost per milligram in the table assumes the whole bottle gets used before that clock runs out. If it does not, the real price is higher than the table says.

What the NASC seal does and does not tell you

Cornell's page makes a point that applies to every bottle here: supplements are not regulated like medications, and products may not contain what they state on the label. It names the National Animal Supplement Council as the body that monitors its members so that ingredients match the label.

The NASC's own page sets out what holding the Quality Seal requires: a written quality control manual, a system for logging adverse events and complaints, compliance with labelling guidelines, the FDA-recommended caution statements where they apply, and random product testing by an independent lab. Nothing on that page says the seal certifies that a product works. What the NASC seal covers, line by line, is worth reading before paying extra for the logo. Check the bottle in hand for the seal itself.

Where fish oil fits in a joint plan

For an older dog with stiff joints, fish oil is one piece of a plan that a vet should be running. Wakshlag, on the Cornell page, says fish oil may help reduce the dose of anti-inflammatory pain medication a dog needs. That is a reason to tell the vet about it, not a reason to change a prescription at home. The other joint supplements with any evidence behind them sit alongside it, and the glucosamine and chondroitin dosing guide covers the products that most often get bought instead of fish oil rather than with it.

Frye also notes that omega-3s should generally be given as a separate product for joint health, because the chews that include them usually contain little.

Questions people actually ask

What should I look for on a dog fish oil label?

The milligrams of EPA and DHA per serving. CSU's veterinary hospital says quality products display both on the label. Total oil, total omega-3 and omega 3-6-9 figures are not the number to compare.

How much fish oil does a dog need?

That is a question for the dog's vet. CSU's chart sets an osteoarthritis maximum of 310mg of EPA and DHA per kilogram to the power 0.75 per day, about 1,623mg for a 20lb dog, and suggests starting near a quarter of that. A healthy dog on a maintenance amount needs far less.

Is liquid fish oil better than capsules?

Not in itself. Liquids are usually cheaper per milligram of EPA and DHA and easier to scale for a big dog. Capsules are tidier and need no measuring. Compare the cost per 1,000mg of EPA and DHA rather than the format.

Can fish oil make a dog gain weight?

Yes. It is fat, and Grizzly states 38 kcal per teaspoon for its oil. Cornell quotes Dr. Christopher Frye saying he never recommends fish oil in overweight dogs, and suggests adding it once the dog is at a healthy weight.

Does the NASC seal mean a fish oil works?

No. The NASC describes the seal as covering quality control, adverse event reporting, labelling and random independent product testing. It is an assurance about the bottle, not about the effect.

Sources

• Cornell Riney Canine Health Center: how joint supplements can help with orthopedic conditions
• CSU Veterinary Health System: canine fish oil dosing chart
• Today's Veterinary Practice: fish oil dosing in pet diets and supplements, Raditic and Gaylord
• NASC Quality Seal requirements
• Welactin Canine Omega-3 liquid, guaranteed analysis and weight chart
• Grizzly Salmon Plus, guaranteed analysis and storage
• Nordic Naturals Omega-3 Pet Soft Gels, supplement facts and weight chart