- Even one pill can be toxic — worse for cats
- Within hours
- Affects: Liver & red blood cells
Why this verdict for dogs
Acetaminophen, the painkiller in Tylenol, damages a dog’s liver and red blood cells. Never give it unless your vet prescribes a specific dose.
Warning signs to watch for
- Vomiting & loss of appetite
- Dark or muddy gums
- Swollen face or paws
- Lethargy
⚠ If your dog ate acetaminophen (tylenol)
Act immediately — don't wait for symptoms.
- Call your vet or a pet poison helpline right away.
- Note how much was eaten and when.
- Do not induce vomiting unless a professional tells you to.
Acetaminophen — sold as Tylenol, Paracetamol or hidden inside combination cold and flu medicines — is in a different category of danger for cats than almost anything else in a household medicine cabinet. It is the classic case of a drug that is routine for humans and potentially fatal for a cat in a single tablet.
How much is safe?
For cats there is effectively no safe amount. A single regular-strength 325 mg tablet can kill an average cat, because cats lack the liver enzyme that lets humans and dogs break the drug down safely. Dogs tolerate it better but not well — liver damage generally starts around 75–100 mg/kg, so a couple of extra-strength tablets is meaningful for a medium dog. Never give either species a human painkiller at home.
What happens if a dog eats too much?
Cats show a very distinctive picture: the drug converts their hemoglobin into a form that cannot carry oxygen, so the gums turn muddy brown or grey rather than pink, breathing becomes fast and laboured, and the face and paws often swell. This can begin within one to four hours. Dogs more typically show liver injury — vomiting, lethargy, loss of appetite, a yellow tinge to the gums or the whites of the eyes — over the following day.
⚠ What to do if your dog ate acetaminophen (tylenol)
This is one of the true 'go now' poisonings, particularly for a cat. Call your vet or a poison line immediately (ASPCA 888-426-4435 · Pet Poison Helpline 855-764-7661) and head to a clinic; brown gums or open-mouthed breathing mean go straight to an emergency hospital without calling first. There is a real antidote — N-acetylcysteine — and it works dramatically better the earlier it is given. Take the packet so the team knows the exact strength.
⚠️ Worried your pet got into this?
Frequently asked questions
Is paracetamol the same as acetaminophen?
Yes, they are two names for the same drug. Anything labelled Tylenol, paracetamol or 'APAP' in a cold-and-flu blend carries the same risk.
Why are cats so much more sensitive than dogs?
Cats are missing most of the glucuronidation pathway the liver uses to package the drug for safe disposal. The leftover toxic byproduct then attacks red blood cells and liver cells.
My cat licked a tablet — is that enough to matter?
Treat it as an emergency and call. Because the toxic dose for a cat overlaps with a single tablet, vets do not wait and watch with this one.
More medications for dogs
By the CanMyPet Editorial Team · Reviewed against ASPCA Animal Poison Control, the American Kennel Club (AKC) and Pet Poison Helpline · Last updated July 31, 2026.
Sources
- ASPCA — People Foods to Avoid Feeding Your Pets
- American Kennel Club — Dog Nutrition
- Pet Poison Helpline — Poison List