Cats are obligate carnivores with unique metabolisms, and several common human foods can cause serious harm or even death. Some of these are well known, like chocolate, while others might surprise you. Here’s what you need to keep away from your cat and why each food is dangerous.
Onions, Garlic, and Related Plants
Every member of the allium family is toxic to cats. That includes onions, garlic, leeks, shallots, and chives in any form: raw, cooked, powdered, or dehydrated. The dangerous compounds are sulfoxides and sulfides, which attack your cat’s red blood cells. Specifically, a compound called n-propyl disulfide interferes with an enzyme that protects red blood cells from oxidative damage. Without that protection, hemoglobin breaks down and forms clumps on the surface of red blood cells called Heinz bodies. The body then destroys those damaged cells faster than it can replace them, leading to anemia.
This is especially sneaky because garlic and onion powder show up in all sorts of human foods: soups, sauces, baby food, seasoning blends, deli meats. Even small repeated exposures can build up over time. Signs of allium poisoning include pale gums, lethargy, rapid breathing, dark or reddish urine, and weakness. Garlic is roughly five times more concentrated than onion, so it takes less to cause problems.
Chocolate and Caffeine
Chocolate contains theobromine and caffeine, both of which cats metabolize far more slowly than humans do. Symptoms appear at roughly 85 mg of theobromine per kilogram of body weight, and deaths have been reported at just 100 mg per kilogram. Caffeine becomes toxic at about 130 mg per kilogram. For a typical 4.5 kg (10-pound) cat, that’s a surprisingly small amount of dark chocolate.
The darker the chocolate, the more dangerous it is. Baking chocolate and dark chocolate have the highest theobromine concentrations, while white chocolate has very little. Signs of poisoning include restlessness, rapid breathing, muscle tremors, vomiting, and seizures. Coffee, tea, energy drinks, and caffeine pills carry similar risks.
Raw Yeast Dough
Unbaked bread dough made with yeast creates a two-part problem. First, the warm environment inside your cat’s stomach causes the dough to keep rising, expanding the stomach and potentially cutting off blood flow to the stomach wall, similar to what happens in a dangerous bloat episode. Second, as the yeast ferments sugars in the dough, it produces ethanol. That alcohol gets absorbed into the bloodstream, causing what amounts to alcohol poisoning: disorientation, metabolic acidosis, and central nervous system depression. Even a small piece of raw dough can be dangerous, since it continues expanding after it’s swallowed.
Grapes and Raisins
Grapes and raisins are well established as highly toxic to dogs, causing acute kidney failure. The picture for cats is less clear-cut but still concerning. Tartaric acid and its salt, potassium bitartrate, are the currently proposed toxic agents. Research from the Journal of Small Animal Practice found that cats are likely less susceptible than dogs to grape-induced kidney injury, with only one published report of two cats developing acute kidney failure after eating grapes. Still, some cats do show symptoms like vomiting and loss of appetite after ingestion. Because the risk isn’t fully understood and individual variation exists, most veterinary toxicologists recommend treating grapes and raisins as unsafe for cats.
Raw Fish
An occasional tiny piece of cooked fish is generally fine, but a diet heavy in raw fish is a real problem. Raw fish contains thiaminase, an enzyme that destroys thiamine (vitamin B1). Thiamine is the only vitamin that has a dedicated enzyme capable of breaking it down, and that enzyme is present in the flesh of many fish and shellfish species. Over time, a raw fish diet depletes your cat’s thiamine reserves, leading to neurological symptoms: loss of coordination, head tilting, dilated pupils, and in severe cases, seizures and coma. Cooking fish deactivates thiaminase, which is why properly prepared fish in commercial cat food is safe.
Raw fish also carries the risk of bacterial contamination and parasites, adding another reason to keep sushi-grade salmon off the menu.
Dairy Products
The image of a cat lapping up a saucer of milk is one of the most persistent myths in pet ownership. Kittens produce the enzyme lactase to digest their mother’s milk, but most cats lose this ability as they mature. Without enough lactase, the lactose sugar in milk passes undigested into the intestines, where bacteria ferment it. The result is gas, bloating, abdominal pain, vomiting, and diarrhea. Dairy won’t poison your cat, but it will make many cats genuinely uncomfortable. If your cat tolerates small amounts without symptoms, it’s not harmful, but there’s no nutritional reason to offer it.
Fatty Table Scraps
Butter, bacon grease, fatty meat trimmings, and fried foods can trigger pancreatitis in cats. The pancreas becomes inflamed, and the symptoms are frustratingly vague: lethargy, reduced appetite, and in about half of affected cats, vomiting or weight loss. According to Cornell University’s Feline Health Center, abdominal pain is only reported in 10 to 30 percent of cats with pancreatitis, likely because cats are skilled at hiding discomfort. Severe acute pancreatitis can make a cat critically ill very quickly, while chronic cases may simmer with subtle signs for months. One fatty meal probably won’t cause a crisis, but regularly sharing greasy human food raises the risk significantly.
Dog Food
A cat stealing a mouthful of dog food isn’t an emergency, but feeding dog food as a regular diet is genuinely dangerous. The critical difference is taurine. Cats cannot synthesize this amino acid on their own because they lack the necessary enzymes, so they need it daily from their food. Dog food is not formulated to meet a cat’s taurine requirements.
Over months of taurine deficiency, permanent damage sets in. The retinas degrade, causing lesions that can lead to irreversible blindness. The heart muscle weakens and stretches, a condition called dilated cardiomyopathy, which can progress to heart failure. Taurine helps regulate the heart’s ability to contract and manage energy, so without it the heart slowly loses function. Dog food also tends to be lower in protein and higher in carbohydrates than what cats need, compounding the nutritional mismatch.
Xylitol: A Surprise Exception
Xylitol, the sugar substitute found in sugar-free gum, candy, and peanut butter, is extremely dangerous for dogs. You might expect it to be equally harmful for cats, but research tells a different story. A study that gave cats xylitol at doses known to cause liver failure and death in dogs found no significant changes in blood chemistry or blood sugar at any tested dose. At the highest dose (1,000 mg per kilogram), there was a mild blood sugar increase, but it stayed within normal range. Cats appear to handle xylitol without the dangerous insulin spike that makes it so lethal for dogs. That said, xylitol-containing products often include other ingredients that aren’t safe for cats, so there’s no reason to offer them deliberately.
Other Foods Worth Avoiding
- Alcohol: Cats are extremely small, and even a tablespoon of liquor can cause dangerous drops in blood sugar, body temperature, and blood pressure.
- Raw eggs: Contain avidin, a protein that interferes with biotin absorption, and carry the risk of salmonella.
- Bones: Cooked bones splinter easily and can perforate the digestive tract. Raw bones can also harbor bacteria.
- Salt in large amounts: Excessive sodium causes vomiting, diarrhea, tremors, and in extreme cases, seizures.
What to Do if Your Cat Eats Something Toxic
Speed matters. If you know or suspect your cat ate something harmful, contact your veterinarian immediately or call the ASPCA Animal Poison Control Center at 888-426-4435 or the Pet Poison Helpline at 855-764-7661. Both lines operate 24/7. Have this information ready: what your cat ate (brand name or ingredient list if possible), approximately how much, when they ate it, and your cat’s weight. Do not try to induce vomiting unless specifically instructed by a veterinary professional, as some substances cause more damage on the way back up.