Is Diclofenac (Voltarol) toxic to cats?
No. Diclofenac (Voltarol) is a prescription-strength NSAID and is toxic to cats by any route — tablets, topical gel, or licked from a treated person's skin. Even a small dose can cause serious harm.
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Key facts
- Verdict: No — dangerous to cats. Diclofenac (Voltarol) should never be given deliberately.
- Category: Human painkiller
- Onset: Signs can start 0–12 hours — see the full timeline below.
- If it's already happened: Call your vet now, or the Animal PoisonLine on 01202 509000 (24/7, charges apply) — see the emergency steps below.
If your cat has just eaten diclofenac (voltarol)
- Wipe off any gel residue from your cat's mouth or fur.
- Call your vet immediately.
- If you can't reach your vet, call Animal PoisonLine (01202 509000) — paid triage, 24/7.
What's the full picture?
Diclofenac belongs to the NSAID (non-steroidal anti-inflammatory drug) family, and cats are markedly more sensitive to NSAIDs than dogs or humans. This is because cats have a much slower and less efficient ability to metabolise many NSAIDs through their liver, meaning the drug and its harmful effects build up rather than being cleared quickly. Where a human might tolerate repeated diclofenac use for arthritis or back pain, a single cat-sized exposure can tip into toxicity, and there is no dose that can be considered 'safe' for a cat outside of a vet-prescribed feline-specific NSAID at a feline-specific dose.
In the UK, diclofenac is most commonly encountered as Voltarol gel, sold over the counter for muscle and joint pain, though oral diclofenac tablets exist on prescription too. Cats are typically exposed in one of a few realistic ways: licking gel residue off a person's hands, arms or legs after it's been applied (cats are drawn to grooming anything unusual on skin or fur they come into contact with), having gel applied directly to the cat in the mistaken belief it might help joint stiffness (never do this), or occasionally chewing through a foil blister strip of tablets left within reach.
Once absorbed, diclofenac blocks the COX enzymes that produce prostaglandins — molecules that, among other things, protect the stomach lining and maintain blood flow to the kidneys. Blocking them causes two main problems: erosion and ulceration of the gastrointestinal tract, which can progress to bleeding ulcers, and reduced blood flow to the kidneys, which can cause acute kidney injury. Both can develop over hours to a few days and both are potentially life-threatening without treatment, particularly in cats that are older, dehydrated, or have any pre-existing kidney disease, which is common in the cat population generally.
There is no way to reliably predict from the outside how much gel was licked or how badly a given cat will be affected, so any known or suspected diclofenac exposure warrants an urgent call to your vet or a poisons information service rather than a wait-and-see approach. Treatment usually involves inducing vomiting if the exposure was very recent, gut-protectant medication, intravenous fluids to support the kidneys, and monitoring bloodwork over the following days.
Symptoms to watch for
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Cat owner essentials
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Questions owners ask
My cat just licked a small smear of Voltarol gel off my leg — how worried should I be?
Contact your vet straight away rather than waiting for symptoms. Because cats are so sensitive to NSAIDs, even what seems like a trivial amount is treated as a genuine exposure that needs professional advice, and early treatment is far more effective than treating established organ damage.
Is any human painkiller safe to give my cat?
No human painkiller — NSAID or otherwise — should be given to a cat without specific veterinary instruction. Cats have their own licensed feline NSAIDs and pain relief options dosed precisely for their metabolism; human products, including paracetamol and ibuprofen, are all dangerous.
How long does diclofenac stay in a cat's system?
Because cats metabolise many drugs slowly, diclofenac can remain active in the body considerably longer than in a human, which is exactly why toxicity builds even from doses that would be minor in a person. Your vet will typically monitor bloodwork for several days after a significant exposure.
Can I use pet-safe joint gels on my cat instead?
Only use products specifically licensed for cats and only under veterinary guidance. Never apply a human topical NSAID gel to a cat, and always keep tubes of Voltarol or similar products stored well away from areas your cat can reach or rub against.
A lockable medicine box is the simplest way to keep human tablets out of reach of a curious cat.
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Related
Sources referenced for this guidance
- Veterinary Poisons Information Service (VPIS) — UK clinical toxicology reference used by vets
- International Cat Care — feline-specific clinical guidance
- BSAVA — British Small Animal Veterinary Association reference materials
- Merck Veterinary Manual — professional veterinary reference
About this guidance
Every entry on this site is compiled from published UK veterinary toxicology sources — International Cat Care, Veterinary Poisons Information Service (VPIS) references, RCVS-registered practice materials, and peer-reviewed feline medicine literature. Where the evidence is mixed, we err on the cautious side because cats are unusually sensitive to many common substances that are harmless to humans and even to dogs.
This is general information written for UK cat owners. It is not personalised veterinary advice for your specific cat, their age, weight, medical history, or the exact exposure you're dealing with. If your cat has eaten something or is unwell, call your vet first. The Animal PoisonLine on 01202 509000 is available 24/7 for a small fee and can tell you whether an emergency visit is needed.
Entries are reviewed and updated as new research emerges. Spotted an error? Let us know — corrections are investigated and applied within 24 hours. For more context on how we work, see about and our full disclaimer.
Last reviewed: · By the What Can My Cat Eat? editorial team