My cat got into Tylenol.
Go to the ER now.
Cats lack the liver pathway that processes acetaminophen. There is no safe feline dose of Tylenol, and one tablet can be lethal.
Published veterinary references are unanimous: cats cannot conjugate acetaminophen, so even part of one regular-strength (325 mg) tablet can cause life-threatening damage to red blood cells and the liver. If your cat chewed, licked liquid medicine, or you even suspect ingestion, go to an emergency vet now and call poison control on the way.
Pet Poison Helpline · 855-764-7661 ASPCA Poison Control · 888-426-4435What it does and how fast
Acetaminophen destroys the blood's ability to carry oxygen (methemoglobinemia) within 1-4 hours: brown or muddy gums, difficulty breathing, weakness, facial swelling. Liver failure signs can follow at 24-72 hours. Early treatment with the antidote (N-acetylcysteine) is highly effective; late treatment often is not.
Where cats encounter it
Dropped pills, children's liquid formulations (sweet-tasting), combination cold medicines, and well-meaning owners dosing a painful cat. Never give a cat any human pain reliever; feline-safe pain control exists but only from your vet.
What NOT to do
Do not wait for symptoms. Do not induce vomiting at home. Do not dose any human painkiller to cats, ever, including baby aspirin and ibuprofen.