Are Onions and Garlic Toxic to Cats?

By Tailwisp Editorial TeamUpdated October 20, 20264 min read

Onions and garlic are kitchen staples that make human food delicious. For cats they are a hidden hazard. Unlike many toxic foods, the effects can be delayed by days, which makes it easy for owners to miss the connection. Knowing why these foods are risky and how to spot trouble can protect your cat.

Why onions and garlic are toxic to cats

Onions, garlic, chives, leeks and shallots belong to the Allium family. They contain sulfur compounds, such as organosulfoxides, that damage red blood cells. The damage is oxidative: the compounds cause hemoglobin to clump into structures called Heinz bodies, and the weakened cells are then destroyed by the body. The condition is called hemolytic anemia.

Cats are especially vulnerable because their red blood cells are more prone to oxidative injury than those of many other species. Veterinary references report that harmful changes can occur at around 5 grams of onion per kilogram of body weight, roughly 2 grams per pound, so a small quantity can matter for a small cat. Garlic is generally considered more concentrated than onion, so even less may cause harm.

Which foods contain them

The risk is not limited to raw vegetables:

• Raw, cooked, fried and dehydrated onion or garlic
• Onion powder and garlic powder in seasoning blends
• Soups, stews, gravy, sauces and stock
• Baby food, which often contains onion powder
• Pizza, pasta dishes and stir-fries
• Hot dogs, deli meats and some pet-store treats made for people
• Chives, leeks, scallions and shallots
• Garlic supplements and some "natural flea remedies" sold online

Cooking does not neutralize the toxins. Dried and powdered forms are more concentrated.

Signs of onion or garlic toxicity

Early signs may be mild, such as drooling, vomiting or diarrhea, and some cats show nothing at first. Anemia often develops over two to four days, and signs include:

• Pale or yellowish gums
• Weakness or lethargy
• Fast breathing or heart rate
• Reduced appetite
• Reddish or brown urine
• Collapse in severe cases

Because the delay is so long, tell your vet if there was any chance your cat ate onion or garlic in the past week, even if your cat seems fine.

What to do if your cat ate onion or garlic

1. Remove the food and work out how much your cat ate and what type it was.
2. Call a veterinarian or poison helpline. In the US, the ASPCA Animal Poison Control Center and the Pet Poison Helpline are open around the clock, and fees may apply. Our US vet directory can help you find a clinic.
3. Follow veterinary advice about vomiting. Do not induce it yourself.
4. Plan a recheck. Your vet may recommend blood tests several days after exposure to look for anemia.

How vets treat it

If the exposure was recent, a vet may induce vomiting and give activated charcoal. Most cats need monitoring and blood tests to track their red blood cell count. Mild cases may need no further treatment, while severe anemia may require hospitalization, oxygen, fluids or a blood transfusion. Most cats recover once the toxin is out of their system and red blood cells regenerate, which takes a few weeks.

Preventing onion and garlic exposure

• Do not feed table scraps without checking every ingredient.
• Keep cooked leftovers covered, particularly soups and sauces.
• Read labels on baby food and treats before sharing.
• Avoid garlic-based remedies for fleas or worms. They are not effective and can be harmful. Use vet-approved products instead.
• Store onions, garlic and shallots in closed bins.

Special case: baby food and seasoned meat

One of the most common routes of onion exposure is food that owners think is cat-friendly. Jarred baby food with meat sometimes contains onion powder, and a spoonful given as a tempting treat for a sick cat can add up over several days. Likewise, rotisserie chicken, lunch meat, hot dogs and flavored cooked meats are usually seasoned with garlic or onion. Read the label, or offer plain home-cooked meat without seasoning instead.

Why signs are delayed

The toxins start damaging red blood cells quickly, but the body takes time to clear the damaged cells and to notice the shortage. That is why a cat may seem fine for a day or two after a meal that included onion, then become pale and weak. If you suspect exposure, ask your vet whether a follow-up blood test is sensible, usually after several days, even if your cat looks normal.

Does a small amount matter?

A single lick of a sauce is unlikely to cause trouble, but repeated small exposures can add up, so do not make a habit of sharing seasoned foods. Be extra cautious with kittens, small adults and cats that already have anemia, kidney disease or heart disease.

What cats can have instead

Plain cooked chicken or turkey, a bit of plain cooked egg and a bite of cooked salmon are safer treats, as long as they are unseasoned and boneless. See our guides on chicken and eggs. Treats should stay a small portion of the diet.

You can look up other foods quickly with our free cat food and plant safety checker, and for a broader look at what is dangerous, read about chocolate and grapes and raisins. If your cat eats something that worries you, call your vet right away.

This article is general educational information, not veterinary advice. Every cat is different. If your cat is unwell, or you are unsure about a symptom, diet change or medication, contact your veterinarian.