Can Cats Eat Tuna With Mayo?

Better not. Tuna with mayonnaise isn’t a good treat for cats. It is rich and fatty, and tuna salad often has onion or garlic, which can harm a cat’s blood. We found no source on plain mayo itself, so we can’t give a safe amount. Plain tuna, in small bites, is a better choice.

Is mayonnaise bad for cats?

We did not find a veterinary source that talks about mayonnaise for cats. So there is no vet-backed safe amount, and we won’t make one up.

What we can say comes from the general advice on rich foods. The ASPCA says very fatty foods can cause vomiting and diarrhea in pets, and in some pets they can lead to pancreatitis. That is a painful swelling of the pancreas, an organ that helps digest food. The ASPCA makes this point about fatty nuts, and the same worry applies to other greasy foods.

The Merck Veterinary Manual says the cause of pancreatitis in cats is usually not known. So fat is not proven to be the cause. Still, a rich food your cat doesn’t need is an easy one to skip.

Cornell’s Feline Health Center also says treats should not be more than 10 to 15 percent of your cat’s daily calories. Cornell calls obesity the most common nutrition problem in cats.

Why is tuna salad the bigger worry?

Tuna salad is more than tuna and mayo. Many recipes add chopped onion, and some add garlic or seasoning. Those are the parts that worry vets most.

Merck’s manual says cats are the animals most easily hurt by onion and garlic. Less than a teaspoon of cooked onion has made cats sick. Garlic is about 3 to 5 times stronger than onion. Raw, cooked, and dried forms can all cause harm.

These foods damage red blood cells. That can lead to anemia, which means the blood cannot carry enough oxygen. Merck says signs usually show up only after a lot of damage, often 3 to 5 days after eating it. Look for:

• Tiredness and weakness
• Not wanting to eat
• Fast breathing
• Yellow skin or eyes
• Dark urine

If you think your cat ate any, call your vet right away. Don’t wait for signs. For more, see our guide on whether cats can eat onions.

The ASPCA also warns that too much salt can make pets very thirsty, and in serious cases cause tremors and seizures. Check the label if the tuna salad came from a store.

What about the tuna part?

Plain tuna has its own limits. The Merck Veterinary Manual says fish-based products have been linked to slow mercury poisoning in cats, mostly hurting the nerves and kidneys. Cornell adds that some cats that ate canned fish made for people developed serious nerve problems. Tuna is a treat, not a meal. Our full guide to whether cats can eat tuna covers how to serve it.

What if my cat ate some tuna with mayo?

Check what was in it.

1. Plain tuna and mayo only: We found no source on how much is too much. Watch for vomiting, diarrhea, or not eating. Call your vet if these last or if your cat seems to be in pain.
2. Onion, garlic, or onion powder in it: Call your vet or a poison hotline now, even if your cat seems fine.
3. A lot of it: Call your vet and ask what to do.

Bring the label or recipe with you if you can.

What can I share with my cat instead?

• A few small flakes of plain canned tuna packed in water, drained, with no salt added, once in a while
• Treats made for cats

Keep treats to a small part of the day’s food, no more than 10 to 15 percent of calories, as Cornell advises. Your cat’s main meals should be a complete cat food. For more foods to avoid, see our list of foods that are toxic to cats.