Why are human painkillers dangerous for pets?
NSAIDs (ibuprofen, naproxen, aspirin) reduce the prostaglandins that protect the stomach lining and keep kidneys filtering. Pets are much more sensitive: dogs can develop stomach ulcers at 8–16 mg/kg of ibuprofen, and kidney failure above ~100 mg/kg. Cats are even more sensitive.
Naproxen is roughly 2× more toxic than ibuprofen, and acetaminophen (paracetamol) is especially dangerous for cats — see the separate paracetamol calculator.
About the dose levels
Thresholds shown are for ibuprofen mg/kg. If you entered naproxen, treat the result as more urgent (multiply dose by ~2).
Thresholds shown are for ibuprofen mg/kg. If you entered naproxen, treat the result as more urgent (multiply dose by ~2).
Signs to watch for
- Vomiting (sometimes with blood), drooling
- Abdominal pain, loss of appetite
- Black, tarry stools (GI bleeding)
- Increased thirst and urination, then kidney failure
- In cats: depression, seizures
What to do right now
- Call your vet or poison line right away with the exact drug and milligram strength.
- Do not wait for symptoms — gut and kidney damage starts silently.
- Do not give milk or food hoping to “soak it up” without vet advice.
- Bring the bottle so the vet knows the exact dose.
If your pet shows any of the signs above, go to the nearest emergency vet now and call ahead.