A cat that has ingested a drug or toxic substance will usually show noticeable changes in behavior, movement, and eye appearance within minutes to a few hours. The specific signs depend on what your cat got into, but the most common red flags are loss of coordination, unusual lethargy or agitation, dilated pupils, vomiting, and tremors. If you’re seeing a sudden combination of these in a cat that was fine an hour ago, something is wrong.
The Most Reliable Warning Signs
Regardless of the substance, intoxicated cats tend to share a cluster of neurological symptoms. The hallmark is ataxia, which simply means your cat is walking like it’s drunk: stumbling, swaying, or unable to walk in a straight line. This shows up with nearly every class of drug, from pain medications to marijuana to antifreeze.
Other signs that cut across most types of poisoning include:
- Dilated pupils that don’t constrict normally in bright light
- Extreme lethargy or sedation, where your cat seems unable to stay awake or respond to you
- Vomiting or drooling
- Tremors or muscle twitching, especially along the back and in the legs
- Heightened sensitivity to sound, touch, or movement, where your cat flinches or startles at things it normally ignores
- Seizures in more severe cases
A cat’s normal resting heart rate is 100 to 140 beats per minute, its breathing rate is 20 to 30 breaths per minute, and its body temperature sits between 100.0°F and 102.5°F. Drug exposure frequently pushes these numbers outside their normal range. A heart rate above 240 bpm, for instance, has been documented in cats exposed to stimulants. If your cat feels unusually hot or cold to the touch, or you can see its sides heaving rapidly while it’s resting, those are additional clues.
Signs by Type of Substance
Marijuana and THC Edibles
THC is one of the most common accidental exposures in household cats, especially with the growing availability of edibles. A cat that has eaten a THC product will typically become very lethargic and uncoordinated, often swaying or falling over. Other distinctive signs include urinary incontinence (your cat may dribble urine without seeming to notice), head bobbing, trembling, and an exaggerated startle response to sounds or motion. Dilated pupils are common. Some cats swing between lethargy and agitation. Body temperature can go either unusually high or unusually low.
Pain Medications (Acetaminophen, Ibuprofen, Aspirin)
Cats are extraordinarily sensitive to human pain relievers. Even a single tablet of acetaminophen (the active ingredient in Tylenol) can be life-threatening. Signs of acetaminophen poisoning develop within one to four hours: your cat’s gums and tongue may turn a brownish or muddy color because the drug destroys red blood cells, and swelling of the face and paws can follow. Liver damage may not become obvious for up to a week.
Ibuprofen and aspirin poisoning look slightly different. Expect vomiting, loss of appetite, depression, and diarrhea. Aspirin toxicity can also cause a fever and, in serious cases, internal bleeding. If you see dark or bloody stool alongside vomiting and lethargy, that combination is highly suspicious.
Flea and Tick Products (Pyrethrins)
Cats are far more sensitive than dogs to pyrethrin-based flea treatments. If a dog-strength product was accidentally applied to your cat, or your cat groomed a recently treated dog, the signs are distinctive. In mild cases, you’ll see paw flicking, ear twitching, and rippling contractions of the skin along the back. In one clinical study of pyrethrin-poisoned cats, 86% had muscle tremors, 41% showed twitching, 41% had heightened skin sensitivity, and 33% had seizures. About one in five cats developed dilated pupils, and 12% experienced temporary blindness.
Antifreeze (Ethylene Glycol)
Antifreeze poisoning is especially dangerous because it progresses in stages and can look mild at first. Within 30 minutes of ingestion, a cat enters what resembles alcohol intoxication: nausea, vomiting, depression, and stumbling. This first stage can last up to 12 hours. Cats may seem to improve temporarily before the substance causes severe kidney damage. Seizures and coma occur in more serious cases. Because the early signs can look relatively minor, antifreeze is one of the most deceptive poisonings.
Stimulants and Opioids
Stimulant exposure (including medications for ADHD or accidental contact with illicit drugs) tends to cause pronounced pupil dilation, a racing heart rate, agitation, and in severe cases, seizures or psychotic-seeming behavior. Opioid exposure looks like the opposite: deep sedation, very slow breathing, and an inability to be roused. A cat on opioids may breathe so slowly that you have to watch carefully to confirm it’s still taking breaths. Respiratory rate drops first and most dramatically, and in severe cases the cat may stop breathing entirely.
How Quickly Symptoms Appear
Most drugs produce visible signs within 30 minutes to four hours. THC and antifreeze tend to act on the faster end of that range, with noticeable changes in as little as 30 minutes. Acetaminophen symptoms develop within one to four hours, though some of the more dangerous effects on red blood cells take 4 to 12 hours to fully emerge. The general rule: if your cat was normal this morning and is now stumbling, vomiting, or acting profoundly “off,” the window of exposure is likely the last few hours.
One complicating factor is that cats are secretive about what they eat. You may not witness the ingestion at all. That’s why a sudden cluster of neurological symptoms in an otherwise healthy cat should always raise suspicion of toxic exposure, even if you didn’t see them get into anything.
What to Do If You Suspect Exposure
Time matters. If you suspect your cat has ingested any drug or toxic substance, contact a veterinarian immediately. If your vet isn’t available, two 24/7 hotlines can guide you: the ASPCA Animal Poison Control Center at 888-426-4435, and the Pet Poison Helpline at 855-764-7661. Both charge a consultation fee, but they can tell you exactly how urgent the situation is and what to do next.
Do not try to induce vomiting at home unless specifically told to by a veterinarian or poison control. Some substances cause more damage on the way back up, and the wrong approach can make things worse. What you can do is gather any evidence of what your cat may have eaten: the pill bottle, the wrapper, the chewed-up edible, or a sample of vomit. This information helps the vet narrow down the substance quickly.
At the veterinary clinic, diagnosis typically involves blood work, urine testing, and sometimes analysis of vomit. The vet will match the results to the clinical signs your cat is showing. There’s no single “drug test” that screens for everything at once, so knowing (or suspecting) what your cat was exposed to speeds up treatment significantly. If there’s an environmental clue, like a chewed blister pack or an open container, bring it with you.
Why Cats Are So Vulnerable
Cats lack several of the liver enzymes that humans and even dogs use to break down common drugs. This is why a dose of acetaminophen that would barely register in a human can kill a cat, and why a flea treatment safe for a 50-pound dog can cause seizures in a 10-pound cat. Their small body size compounds the problem: even a tiny amount of a substance produces a high concentration in the bloodstream. Cats are also meticulous groomers, so anything that lands on their fur, from a spilled pill to a topical medication, will almost certainly be licked off and swallowed.