Pet supplements / best of
Best evidence-backed pet supplements.
The supplements whose headline active has genuine research behind it, ranked on our rubric. Strong evidence for the ingredient is the starting point, not the whole score.
Most of the pet-supplement aisle is sold on mechanism and testimonial, not outcomes. Our Evidence Quality sub-score is the heaviest dimension in the supplement rubric for exactly that reason: every scored active is pinned to the primary literature in our evidence library, and the tier reflects what controlled studies actually found, not what the bottle claims. This list is the subset whose headline active clears a tier of 6 or better, the level where the research is at least reasonably supportive.
Omega-3 fish oil sits at the top of the evidence ladder, with the best data of any pet supplement, mainly for osteoarthritis comfort and secondarily for skin. Below it are the studied-form joint actives, undenatured type II collagen and green-lipped mussel, and the strain-specific probiotics with controlled trials for acute diarrhea. What you will not find here are the actives the evidence does not support, such as L-lysine for feline herpesvirus or a general multivitamin for a healthy pet; those are honest about their weak tier and rank elsewhere.
Good evidence for the ingredient is the start of the analysis, not the end. A well-evidenced supplement can still lose points for a hidden or low dose, a long inactive list, or a high cost per day, so this list ranks by full composite. Scores are our opinion under a published rubric, not veterinary advice.
11 supplements
Ranked by PetScored composite.
- 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.
Dogs & catsSkin & coatNASC seal8.8Strong - 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.
Dogs & catsSkin & coatNASC seal8.5Strong - 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.
Dogs & catsSkin & coatNASC seal8.4Good - Nutramax Denamarin Tablets for Dogs (Medium)
The studied SAMe and silybin combination at the dose used in the canine trial, fully disclosed; moderate evidence and a high cost per day keep it Good.
Dogs & catsLiver7.9Good - YuMOVE Joint Care for Adult Dogs
A disclosed green-lipped-mussel-forward chew, NASC-sealed and well priced; a modest GLM dose for a larger dog keeps it Good rather than Strong.
DogsJointNASC seal7.9Good - 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.
CatsSkin & coatNASC seal7.8Good - 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.
CatsSkin & coat7.8Good - 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.
DogsSkin & coat7.6Good - Purina Pro Plan Veterinary Supplements FortiFlora Canine Probiotic
A single studied strain from a manufacturer that owns its plants, but no NASC seal or independent testing and a high cost per day; lands Mixed.
DogsGut & digestive7.1Mixed - Purina Pro Plan Veterinary Supplements FortiFlora Feline Probiotic
The feline twin of FortiFlora: one studied strain from an owner-operator manufacturer, but no NASC seal, no independent testing, and a high cost per day; Mixed.
CatsGut & digestive7.1Mixed - Virbac Vetasyl Fiber Capsules
The one hairball product built on fiber, which is the only hairball approach with controlled cat evidence: a randomized trial found a dose-dependent drop in trichobezoars from a specific fiber, and a second study found psyllium plus higher dietary fiber raised fecal hair excretion in long-haired cats. The label is clean, NASC-sealed, and weight-scaled, with psyllium disclosed at 490 mg per capsule. The catch is dose: the trials raised total dietary fiber to 11 to 15 percent of the diet, and a single 490 mg capsule is far smaller than that, so the label does not prove a daily capsule delivers a studied-effective amount, and Value is flagged approximate. Still the best-evidenced option in a category whose alternative is petroleum gel with no efficacy trial.
CatsHairballNASC seal7.1Mixed
FAQ
Frequently asked
Which pet supplement has the strongest evidence?
Omega-3 fish oil (EPA and DHA). It has the best controlled-trial evidence of any pet supplement, most clearly for reducing osteoarthritis pain and supporting skin and coat. It earns the top evidence tier in our library and tends to lead this list.
How do you decide what counts as evidence-backed?
Each active is tied to an entry in our evidence library, pinned to primary studies (with PMIDs or DOIs), and scored on a tier that reflects what controlled research found. This list includes products whose primary active scores at least 6 out of 10 on that Evidence Quality dimension. Below that, the research is too thin or too mixed to call the ingredient evidence-backed.
If the evidence is good, why isn't every product here a top score?
Because evidence is one of five dimensions. A supplement with a well-evidenced active can still score Mixed if it hides the dose in a proprietary blend, under-doses the studied amount, or costs far more per day than peers. The composite weighs all five, so the list ranks by overall score, not evidence alone.
This ranking is our opinion under a published rubric, not veterinary advice. Affiliate links on individual scorecards never affect the score. See the affiliate disclosure and medical disclaimer.