Cat Medication Safety Checker

Why a cat is not a small dog

The first mistake in home pet care is scaling a human dose down by weight. The second is scaling a dog dose down by weight and giving it to a cat. Neither works, because the difference between species is not size, it is how the liver breaks a drug down.

Cats are short on a group of liver enzymes called glucuronyl transferases, which other mammals use to attach a sugar molecule to a drug so it can be flushed out. With that route running slowly, a drug that a dog clears in hours can sit in a cat's bloodstream far longer. The FDA's Center for Veterinary Medicine makes the point directly about acetaminophen: cats lack the enzymes the liver needs to break the drug down safely (FDA, checked October 2026).

Body size compounds the problem. A 10 pound cat weighs 4.54 kg, roughly 6 percent of a 70 kg adult. A tablet built for that adult is therefore 15 times the per-kilogram amount, and the slower clearance means the exposure lasts longer as well. Two effects stack, and that is why a single tablet can be an emergency rather than a large dose.

The table shows what one 325 mg tablet means at different cat weights, and why the number on the bottle never transfers cleanly from one animal to another.

There is also no reliable home conversion between dog and cat doses. Veterinary formularies list separate feline dose rates for a reason, and many drugs that are routine in dogs are listed as toxic or contraindicated in cats. If a product label mentions dogs only, it does not apply to your cat.

Acetaminophen is fatal to cats

Acetaminophen, sold as Tylenol and included in many cold and flu combinations, is the clearest case in veterinary toxicology. The FDA states in its guide to pain relievers for pets that acetaminophen is fatal to cats and that cats should never be given it, while noting that veterinarians sometimes use it in dogs but never in cats. Cornell University's veterinary hospital small animal toxin list puts it as contraindicated in cats at any dosage (Cornell University College of Veterinary Medicine, checked October 2026).

That phrase, at any dosage, is the whole point. There is no small amount that is safe to try at home, no weight-based formula to apply, and no reason to wait for symptoms before calling for help.

The harm runs on two tracks. The liver suffers dose-dependent damage, and the red blood cells lose their ability to carry oxygen, which is the effect cats are prone to. A cat that has swallowed a tablet may look normal for hours, then develop brown or blue gums, labored breathing, swelling of the face or paws, and collapse.

Hidden sources matter as much as the bottle. Combination cold medicines, nighttime formulas, sinus products and some prescription painkillers contain acetaminophen without the word on the front of the box. A dropped tablet, a chewed blister pack or a spilled purse is enough. Assume any swallowed amount is an emergency and call your veterinarian or a poison control line immediately.

Ibuprofen, naproxen and aspirin

The other common pain relievers are nonsteroidal anti-inflammatory drugs, or NSAIDs. Ibuprofen (Advil, Motrin) and naproxen (Aleve) are not approved for veterinary use at all, and Cornell lists ibuprofen as toxic to dogs, cats and ferrets. The FDA adds that no NSAID is currently approved for long-term use in cats, which tells you how narrow the safe window is even for the drugs a vet does prescribe.

NSAIDs work by blocking the COX enzyme, which cuts the production of prostaglandins. That reduces pain and inflammation, and it also removes part of the protection that keeps the stomach lining intact and keeps blood flowing to the kidneys. In a cat, the result can be stomach ulcers, kidney injury or both, and the margin between a therapeutic dose and a damaging one is small.

Aspirin sits in a different place from the other two. It has been used in cats under veterinary direction, but toxicity is dose dependent and the safe interval is narrow, so the dose has to come from a vet who knows your cat's weight, kidney function and other medications. The same is true of antihistamines, which are sold as harmless sleep aids and are anything but harmless in a 4 kg animal.

Never combine products either. Two NSAIDs at once, or an NSAID with a steroid such as prednisone, raises the risk of gastrointestinal damage, which is why the FDA tells owners to list every medication a pet is taking before adding another.

A worked example: one tablet in a 10 lb cat

Numbers make the risk concrete. Suppose a 10 pound cat eats one regular-strength acetaminophen tablet, 325 mg, off the floor.

Convert the weight first: 10 x 0.45359237 = 4.5359 kg, which rounds to 4.54 kg. Then divide the dose by the weight: 325 / 4.5359 = 71.65 mg per kg, or 71.7 mg per kg.

Now compare it with the adult who owns the bottle. One 325 mg tablet for a 70 kg adult is 325 / 70 = 4.643 mg per kg. The cat's exposure is 71.65 / 4.643 = 15.43 times the adult's per-kilogram amount, so the same tablet delivers about 15.4 times as much drug per kilogram of body weight.

Run the same arithmetic for an 8 pound cat and a 200 mg ibuprofen tablet. The weight is 8 x 0.45359237 = 3.6287 kg, and 200 / 3.6287 = 55.12 mg per kg. The adult share of that tablet is 200 / 70 = 2.857 mg per kg, so the cat gets 55.12 / 2.857 = 19.3 times as much per kilogram. Two tablets in a 12 pound cat: 12 x 0.45359237 = 5.4431 kg, 2 x 200 = 400 mg, and 400 / 5.4431 = 73.49 mg per kg.

The calculator on this page does exactly this arithmetic and stops there. It will not tell you a safe dose, because no safe at-home dose exists for the first two drugs in the list, and for the others the dose depends on things a page cannot see: kidney values, liver values, other medications and the reason for treating.

Milligrams, milliliters and the unit trap

Most dosing errors that reach a poison control line are unit errors, not arithmetic errors. Human medicine and veterinary medicine use the same words for different things, and a number copied without its unit is meaningless.

Two conversions cover most of the ground. To go from pounds to kilograms, multiply by 0.45359237: a 12 pound cat is 5.44 kg. To go from a mg/kg dose to a total dose, multiply by the weight in kilograms: 2 mg/kg in a 5.44 kg cat is 10.88 mg, and at 5 mg/mL that is 10.88 / 5 = 2.18 mL.

The trap is the middle step. A dose written as 1 mg/lb is 2.2046 mg/kg, so treating the two as equal under-doses by more than half. Veterinary labels in the United States often use mg/lb while textbooks use mg/kg, and a decimal point moved one place is a tenfold error. Write the unit next to every number, every time.

What to do if your cat ate something

Call before you calculate. The arithmetic on this page tells you how large the exposure was, not what to do about it, and the treatment window for acetaminophen and NSAID poisoning is measured in hours.

• Call your veterinarian first. They know your cat, can start treatment, and can tell you whether to come in.
• Call a poison control line if your vet is closed. The ASPCA Animal Poison Control Center is at 888-426-4435 and the Pet Poison Helpline at 800-213-6680, both around the clock and both charging a consultation fee, as Cornell's hospital notes.
• Have the package in hand. The strength, the count and the ingredients decide the risk. Bring the bottle, even if it is empty.
• Note the time. "About an hour ago" and "sometime last night" lead to different decisions.
• Do not induce vomiting unless a vet tells you to. Some products cause more damage coming back up.
• Do not wait for symptoms. Cats hide illness, and the first visible sign can come after the damage is done.

Symptoms worth reporting immediately include vomiting, drooling, wobbliness, fast or labored breathing, brown or pale gums, facial swelling, and hiding more than usual. A cat that seems fine is not evidence of a small exposure.

This page is general safety information, not veterinary advice, and it cannot diagnose or treat your cat. For any suspected poisoning, contact a veterinarian or an animal poison control service now.

Keeping medicine away from cats

Prevention is unglamorous and effective. Most cat poisonings in the home involve a pill that was dropped, a bottle that was left open, or a product that was set down for a moment.

• Take pills over a closed drawer or a counter with a lip, never over an open floor.
• Keep medicine in a closed cabinet, not on a nightstand. Cats climb, and a child-proof cap is not cat-proof.
• Sweep the floor after taking anything. A dropped tablet takes seconds to find and seconds to lose.
• Never leave a purse or backpack open on the floor. Loose pills collect in the lining.
• Store pet medicine separately from human medicine, and label the cat's bottle with the cat's name.
• Check combination products for acetaminophen before you take them near a cat, and never leave the bottle out.

Two more habits are worth building. First, never give any medication to a cat without asking a vet, including supplements, essential oils and "natural" remedies, because the label "natural" says nothing about feline safety. Second, tell your vet every product the cat can reach, including flea treatments made for dogs, since a product applied to a dog in the same house can end up on a cat that grooms the dog's bedding.

Finally, keep the poison control numbers where you can find them in a hurry: on the fridge, in a phone note, or both. In an emergency, the thirty seconds spent searching for a number is thirty seconds of exposure you cannot get back.