Fish oil for dogs with arthritis: what the evidence shows

By the PetFishOilGuide editorial team · Updated October 13, 2026 · How we compare

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Studies of dogs with osteoarthritis found modest improvements at higher EPA+DHA intakes than general maintenance, and those doses are set by veterinarians. Fish oil is not shown to cure arthritis. If your dog has stiffness or limping, see your vet first, and do not change prescribed medication on your own.

Many owners arrive here after a vet visit or after watching an older dog struggle on stairs. This page summarizes what published sources say, with the limits stated. It has not been checked by a veterinarian, it makes no treatment claim, and it gives no arthritis dose.

What one large trial found

The most-cited study we could verify is a randomized clinical trial in Journal of Veterinary Internal Medicine ("Dose-titration effects of fish oil in osteoarthritic dogs," Fritsch et al., 2010, PubMed 20707845; abstract checked via Europe PMC on 2026-10-13). It enrolled 177 client-owned dogs with stable chronic osteoarthritis of the hip or stifle (knee). Dogs ate either a baseline therapeutic food or foods with roughly two or three times the EPA+DHA. Blood levels of EPA and DHA rose with the food concentrations. Dogs on the three-times food showed significant improvements in lameness, weight bearing and overall arthritic condition compared with baseline, but dogs on two times did not. The authors concluded that higher fish oil doses produce dose-dependent increases in serum EPA and DHA and modest improvements in clinical signs.

Read it with care. The effect described is modest. It appeared at the higher intake, not the lower. And it was a diet study under study conditions, so it does not tell you what a store-bought supplement will do for your dog. The trial lasted 90 days, with veterinarians assessing the dogs on days 0, 21, 45 and 90, and both vets and owners were blinded to which food a dog received.

Why the doses are for veterinarians

Colorado State University's veterinary hospital publishes a canine fish oil dosing chart for osteoarthritis. It states a maximum of 310 mg of combined EPA and DHA per kg^0.75 per day, intended for veterinarians, and it advises starting at about a quarter of that and increasing slowly while monitoring for side effects. It also says the maximum is not tolerated by all dogs (CSU). CSU presents it as a maximum used in a veterinary chart, not as an owner's target. We show it as a reference only. It is not our recommendation, and our calculator does not output it.

To see why this matters, compare it with the general range. A veterinary nutritionist, Cailin Lenox, writes that she typically doses fish oil at 50 to 75 mg of EPA+DHA per kg for dogs (Today's Veterinary Practice, 2016). The CSU maximum for a 22.7 kg (50 lb) dog is almost twice the top of that range (about 3,230 mg a day against 1,700 mg). Another review states that therapeutic doses across conditions run 50 to 220 mg per kg and that adverse effects appear to be dose-dependent (dvm360). The National Research Council's safe upper limit for adult dogs is about 370 mg x kg^0.75 including food, so higher intakes need professional monitoring.

A veterinary surgeon summarizing the topic for a trade publication also calls 310 mg x kg^0.75 the recommended beneficial dose for osteoarthritis (Veterinary Practice News, 2019). Veterinary Practice News attributes the figure to Bauer (JAVMA, 2011). CSU treats it as a ceiling to work up to under veterinary care, and a 2025 review (Blanchard) says the best dose is unclear, so we do not treat it as settled.

How long until anything changes?

We cannot give a verified time to improvement for a supplement. The CSU page does not state a timeline, and the one trial we read ran 90 days with assessments at 21, 45 and 90 days, which is not a promise for any product. Treat any "works in two weeks" claim you see elsewhere as unverified. If you and your vet decide to try fish oil, ask for a clear plan: what you will watch for (stairs, getting up, play), when you will reassess, and what would make you stop.

Questions to ask your vet

• Is fish oil reasonable for my dog's stage of arthritis and other conditions?
• What daily amount of EPA+DHA, counting food and supplements, should I aim for?
• How much EPA+DHA is already in my dog's food?
• Does it interact with my dog's pain medicine, especially NSAIDs? Veterinary authors list supplements affecting platelets as a concern with drugs such as aspirin and NSAIDs (dvm360).
• When should we recheck, and what side effects mean I stop?

Possible side effects include loose stool, vomiting and weight gain (extra calories matter for arthritic dogs, where weight affects joints). See the side effects guide.

Using the calculator without overreaching

If your vet agrees to a supplement and gives you a daily EPA+DHA target, use that number. If the vet says the general adult range is fine, the dosage calculator converts it into milliliters or softgels for a product you choose. It shows the maintenance range only, never an amount above 75 mg per kg, and it says so if one serving of a product is already above the range. The NRC upper limit, which includes the food, is background information. Pick a product with EPA and DHA printed on the label; see the comparison, and read omega-3 for dogs for background. How we gather label data is on the methodology page.

What this page cannot tell you: whether your dog's pain is from arthritis, which other treatments matter, or whether fish oil is right now. Limping, pain, or sudden changes need a vet visit.