Fisetin for Dogs and Cats: What Owners Need to Know (2026)

Is fisetin safe for dogs and cats?

There is no established safe or effective supplemental fisetin dose for dogs or cats, and controlled veterinary efficacy and safety evidence is insufficient. Mouse and human studies cannot establish how a particular fisetin product behaves in either companion-animal species. Feline differences in the metabolism of some phenolic compounds add a specific concern, but fisetin's pharmacokinetics in cats have not been adequately characterised.

Do not give a pet your own fisetin supplement or try to convert a human study dose by body weight. Discuss any proposed product with the veterinarian who knows your animal's medical conditions and medicines. For the human evidence, see our clinician's guide.

Why are pet owners asking about fisetin?

Interest comes partly from laboratory research on cellular senescence and the availability of supplements marketed for ageing. The original mouse research provides a hypothesis worth investigating, not evidence that fisetin improves lifespan, arthritis, cognition or cancer outcomes in dogs or cats [1].

Differences in drug metabolism, disease, age and formulation make translating doses from mice or humans particularly unreliable in veterinary care.

What has actually been tested in dogs?

A 2024 randomized, blinded veterinary study enrolled 70 senior dogs with mild-to-moderate cognitive impairment to test LY-D6/2, a proprietary combination of a senolytic and an NAD+ precursor [6]. Owner-rated cognition differed between groups at three months (p=0.02), but investigators found no significant between-group difference in in-house cognitive tests or objectively measured activity. Adverse events were similarly distributed across groups.

This was not a standalone fisetin trial. The report does not establish that LY-D6/2 contains fisetin, and its results provide no basis for choosing a dose or predicting fisetin efficacy in dogs. It also tells us nothing about feline fisetin safety.

How does fisetin behave differently in dogs and cats?

Dogs: exposure and safety remain unknown

Dogs cannot be assumed to absorb, metabolise or eliminate fisetin like people. No validated dose–exposure relationship establishes that scaling by body weight produces comparable levels, and laboratory senolytic concentrations cannot be used as a treatment target in dogs [2].

Cats: species-specific metabolic uncertainty

Cats have important, documented limitations in glucuronidating certain phenolic drugs, including a nonfunctional UGT1A6 pathway [3] [4]. However, their ability to conjugate compounds varies by substrate and enzyme, and fisetin-specific feline clearance has not been established. It would therefore be incorrect to predict how much fisetin accumulates, prescribe a proportionally lower feline dose or infer safety from another flavonoid. Avoid self-administering concentrated fisetin to cats.

Isn't fisetin the same kind of compound as onion and garlic?

A common question from pet owners: since onions and garlic are toxic to dogs and cats, and fisetin is also a plant compound, is fisetin dangerous too? No. Onion and garlic toxicity works through an entirely different mechanism — organosulphur compounds that damage red blood cells and cause a specific type of anaemia, unrelated to flavonoid chemistry [5]. Fisetin and other flavonoids don't share this mechanism. Strawberries, apples, and other fisetin-containing fruits aren't toxic to dogs or cats the way onions and garlic are.

That said, some fisetin-containing foods aren't appropriate for pets for unrelated reasons — grapes and raisins are toxic to dogs' kidneys, and cats generally don't tolerate fruit well as part of their largely carnivorous diet. Dietary fisetin isn't a practical route for pets either way.

What dose of fisetin is used for dogs and cats?

There is no validated supplemental fisetin dose, dosing frequency or administration method for dogs or cats. Online schedules derived from human or mouse studies are not veterinary dosing recommendations. Neither monthly pulses nor administration with a fatty meal has been shown to improve safety or efficacy in pets.

Do not divide a human capsule according to a pet's weight or experiment with lower doses in cats. A veterinarian can review the ingredient list, potential medication interactions and whether any evidence-based alternative is more appropriate for your animal's condition.

What about fisetin for dogs with cancer?

Fisetin has documented anti-cancer activity in cell culture and animal models across several cancer types, and some pet owners have asked their vets about it as a complementary option for cancer diagnoses such as mast cell tumours, a common canine skin cancer. No published veterinary study has tested fisetin, alone or combined with other flavonoids, as a treatment for canine mast cell tumours or any other veterinary cancer — this is theoretical extrapolation from human and laboratory data, not established veterinary oncology. Dogs with cancer should be managed by a veterinary oncologist, and fisetin should never substitute for prescribed veterinary treatment such as chemotherapy or surgery.

When should you avoid giving fisetin to a pet?

A concentrated fisetin supplement should not be started without veterinary guidance. Particular concerns include cats, puppies and kittens, pregnancy or nursing, chronic liver or kidney disease, cancer therapy, other prescription medicines and upcoming surgery. Human supplement excipients may introduce additional animal-specific risks.

If your pet is already taking fisetin, tell the veterinarian what product, dose and frequency you used. Before surgery, follow that veterinarian's specific instructions for withholding supplements; no fisetin-specific seven-day withdrawal interval has been established.

Further reading: the separate human safety evidence; medication interactions reported or suspected in human research. Human medication and safety studies cannot be transferred directly to pets.

What we still don't know

We lack reliable species-specific pharmacokinetic studies, repeat-dose safety data, validated dosing ranges, veterinary drug-interaction studies and controlled evidence of clinical benefit. In particular, feline UGT differences identify a reason for caution but do not quantify fisetin toxicity or determine a safe feline dose.

Bottom line

Fisetin has intriguing preclinical biology but no established role in treating ageing or disease in dogs or cats. Do not give pets human fisetin supplements or attempt experimental dose scaling. Discuss any supplement with a veterinarian, especially for cats or animals taking medication. For context, see our human fisetin guide and bioavailability review.