Serious severity
Paracetamol (Acetaminophen) Poisoning
Cats cannot process paracetamol safely. A single ordinary human tablet can be fatal, and there is no safe dose at any weight — this is always an emergency.
⚠️ Common symptoms
Paracetamol is so ordinary in a human medicine cabinet that it is hard to believe how dangerous it is to cats. Yet it is one of the most lethal household poisonings a cat can encounter, and the tragedy is that most cases are acts of kindness — an owner watching a limping or clearly uncomfortable cat, reaching for the only painkiller in the house.
The problem is a gap in feline biochemistry. Most mammals detoxify paracetamol chiefly by glucuronidation, attaching a sugar molecule to the drug so it can be excreted harmlessly. Cats have very limited capacity for this pathway. Faced with a dose, their liver is forced down an alternative route that produces a highly reactive metabolite, normally mopped up by an antioxidant called glutathione. A cat's glutathione reserves are exhausted almost immediately, and the metabolite is left free to do damage.
It does that damage in two places at once. It oxidises the iron in haemoglobin, converting it into methaemoglobin, which is chemically incapable of carrying oxygen. This is why the earliest and most striking sign is a change in gum colour — brown, grey, or a muddy blue rather than healthy pink — accompanied by fast breathing and weakness, as a cat with adequate red cell numbers nonetheless suffocates internally. At the same time the metabolite attacks liver cells, so a cat that survives the first crisis may develop liver injury and jaundice a day or two later. Distinctive facial and paw swelling, which is not well explained, is another characteristic feature in cats.
The antidote, acetylcysteine, works by replenishing glutathione so the liver can neutralise the toxic metabolite. It is genuinely effective, but its usefulness declines sharply with delay, which is why veterinary advice on this poisoning is unusually blunt: go now, before symptoms appear. Cats presented within a few hours frequently do well; cats presented once they are blue and breathless are in a far more precarious position.
The message for owners is uncomplicated. There is no safe dose of paracetamol for a cat, no matter how small the animal or how carefully the tablet is divided, and the same caution applies to ibuprofen, aspirin and other human painkillers. If your cat seems to be in pain, that is a reason to phone the vet, not to open the medicine cabinet — safe and effective feline pain relief exists, and your vet can prescribe it.
🔍 Causes
Almost every case is well-meaning: an owner sees a cat in pain and offers a human painkiller, or a child's liquid paracetamol, not realising how dangerous it is. Cats lack sufficient glucuronyl transferase, the liver enzyme that mammals use to conjugate and safely excrete paracetamol, so they divert the drug down a secondary pathway that generates a toxic metabolite. That metabolite oxidises haemoglobin into methaemoglobin, which cannot carry oxygen, and damages liver cells directly. Cats also swallow dropped tablets or lick spilled syrup, and paracetamol is a hidden ingredient in many combination cold and flu remedies.
🛡 Prevention
Never give a cat any human medication unless a vet has specifically prescribed it for that cat. Keep all tablets, capsules and liquid medicines in closed cupboards rather than on bedside tables or worktops, and pick up dropped pills immediately. Be alert to combination products — many cold, flu and codeine preparations contain paracetamol under names such as acetaminophen, and remember that pet-safe pain relief for cats exists and should be obtained from your vet.
💊 Treatment
This is treated as an emergency at a veterinary practice, and there is nothing useful an owner can do at home. Vets may induce vomiting or give activated charcoal if the exposure was very recent, then give the antidote acetylcysteine, which restores the liver's depleted supply of protective glutathione. Supportive care includes intravenous fluids, oxygen, sometimes a blood transfusion for severe methaemoglobinaemia, and liver protectants such as SAMe or silybin. Outcomes depend heavily on how quickly treatment begins. Never attempt to make a cat vomit at home.
⚕️ Medical disclaimer
- This information is educational only and is not a substitute for veterinary advice.
- Symptoms overlap between conditions — only a vet can diagnose accurately.
- Never withhold treatment or self-medicate based on information found online.
- When in doubt, call your vet. Early intervention almost always leads to better outcomes.