Pet supplements / active ingredient
Fish oil (omega-3 EPA/DHA).
If you only remember one thing from this page: among the actives sold for joints, this is the one with the best evidence behind it, and it is not what the joint aisle is built on. The 2022 meta-analysis found clear analgesic benefit for omega-3 in dogs and cats that already have osteoarthritis, which is the strongest joint finding anywhere in our library.
Read that claim narrowly, because the trials did. It was measured in animals already diagnosed. Nothing here shows that starting a healthy young dog on fish oil prevents joint disease later, and any label implying otherwise has gone past its evidence. Prevention is a marketing word on this shelf, not a trial result.
There is a second, weaker line of evidence for skin and coat, stronger in dogs than in cats, and in the best feline trial the omega-3 arrived through a complete diet rather than a bottle. That matters when you read a cat product's claim: the study design and the product on the shelf are not the same thing.
Evidence grades are PetScored's reading of the published record under our methodology, not veterinary advice and not a claim about what will happen to your animal. If your dog or cat is stiff, sore, or slowing down, that is a conversation with your vet, not a shopping decision.
The evidence
What the published record supports, claim by claim.
Systematic review and meta-analysis found clear clinical analgesic efficacy for omega-3 diets and supplements in canine and feline osteoarthritis, the strongest evidence of any joint active in the library.
Sources: Barbeau-Gregoire 2022 systematic review and meta-analysis, IJMS; Roush 2010 canine OA omega-3 RCT, JAVMA
Species-specific RCT support that essential-fatty-acid / omega-3 supplementation improves canine atopic dermatitis scores and reduces the dose of conventional therapy needed; overall evidence quality is moderate and mixed across formulations.
Sources: Glos 2008 EFA-enriched diet canine atopic dermatitis RCT, Vet Dermatol; 2024 PUFA oclacitinib dose-sparing canine atopy RCT, Vet Dermatol
Feline-specific evidence is real but thinner than the dog data: a 2025 double-blinded RCT found an EPA/DHA-elevated diet roughly halved medication need in cats with feline atopic skin syndrome, and a 2021 peer-reviewed systematic review grades dietary fatty acids as low-to-moderate efficacy. The strongest trial delivered omega-3 via a complete diet, not a standalone supplement, so the label supports a plausible skin and coat benefit without proving it for an individual cat.
Sources: Watson 2025 EPA/DHA diet feline atopic skin syndrome double-blinded RCT, Animals (Basel); Mueller 2021 systematic review of feline atopic syndrome treatment, Vet Dermatol
What the labels disclose
8 of 9 disclose a dose we can compare against the studied range.
A named ingredient is not a dose. Of the 9 products we score with Fish oil (omega-3 EPA/DHA) as the primary active, 3 reach the amount used in the trials, 5 land part of the way there, and 0 do not disclose enough to tell. Cost of a day's serving runs $0.13 to $0.60.
On this site these products are shelved under Skin & coat, which is worth knowing if you were browsing a different category and never saw them.
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Nordic Naturals Omega-3 Pet Soft Gels
The strongest-evidence omega active, fully disclosed in triglyceride form and third-party tested; a partial per-softgel dose for a larger dog keeps it just under the top.
Zesty Paws Wild Alaskan Salmon Oil
A disclosed, well-dosed salmon and pollock omega oil, NASC-sealed and inexpensive per day; strong execution puts it near the top. The Feb 2025 Zesty Paws recall covered soft chews, not this oil.
Grizzly Salmon Plus Wild Salmon Oil
High disclosed EPA and DHA per pump in natural triglyceride form, NASC-audited, and inexpensive per day; strong execution lands it at the top of Good.
Nordic Naturals Omega-3 Cat
A triglyceride-form fish oil third-party tested for purity and keyed to the feline skin and coat evidence; a typical cat reaches only a partial share of the studied EPA and DHA dose at the labeled serving, which keeps it Good rather than Strong.
Nutramax Welactin Feline Omega-3
A disclosed fish-oil liquid delivering an EPA and DHA dose near the feline dermatology target, keyed to the cat skin and coat evidence; well made, though the fish-oil form is not stated and the scoop count is derived.
Vetoquinol Triglyceride OMEGA (Medium Dog)
A fish-oil softgel that discloses EPA and DHA separately in the more bioavailable triglyceride form, NASC-sealed and fairly priced, keyed to the skin and coat claim; the omega evidence for skin sits a notch below the joint tier and the per-softgel dose is moderate, so clean execution lands it Good.
Nutramax Welactin Canine Omega-3 Softgels
A disclosed, well-made omega-3 keyed to the skin and coat claim (a notch below the joint evidence tier); solid execution and value land it Good.
VetriScience Omega 3,6,9 Gel Caps
Discloses EPA and DHA separately in an NASC gel cap from a maker that owns its cGMP plant, but the weight-scaled label dose delivers only about 20 mg/kg/day of EPA plus DHA, below the studied skin and coat range, and there is no independent testing.
Coromega Pup Packets Condition (Skin & Immune)
An emulsified fish-oil packet that discloses EPA and DHA separately and reaches a borderline-adequate skin and coat dose at one packet, at a fair price; but its NASC claim is not in the current directory so we do not credit it, and there is no independent testing.
Evidence grades come from our supplements methodology. Every grade on this page is pinned to a named primary source; where the evidence is thin or contested, we say so rather than rounding it up.