Why
Plain cooked potato is not toxic to cats, but it is not good for them either. PetMD's veterinary guide calls potatoes empty calories for cats and points out that cats are poorly suited to digesting carbohydrates. Mashed potato is mostly starch, so it adds calories without giving a cat anything its complete cat food does not already provide.
The potato itself needs care. PetMD's guide explains that raw potatoes, potato skins, green spots and every part of the potato plant contain solanine, a toxin, and that the skin contains solanine whether it is raw or cooked. That is why mashed potato for a cat has to be made from peeled potato cooked until soft.
Mashed potatoes made for people are the bigger problem. They are usually made with butter, milk or cream and salt, and often with garlic, onion or chives. The ASPCA warns that garlic, onions and chives can damage red blood cells and lead to anemia, and that cats are more susceptible than dogs. It also notes that milk and other dairy products can cause diarrhea or other digestive upset, because pets do not have much lactase, the enzyme that digests milk sugar.
Risks to watch for
- Garlic, onion, chives or scallions, including garlic mashed potatoes and mash seasoned with garlic or onion powder
- Butter, milk, cream, cheese and sour cream
- Gravy, which is fatty and salty and often made with onion
- Salt and seasoning blends
- Potato skins, including skin-on or rustic mash
- Raw or undercooked potato, potatoes with green spots, and sprouting potatoes
- Vomiting or diarrhea after eating it
How to share safely
- Set aside a small piece of potato before you add butter, milk or seasoning.
- Wash and peel it, and do not use a potato with green spots.
- Boil or steam it until it is soft all the way through. Add no salt, oil or seasoning.
- Mash it with a little plain water instead of milk or butter.
- Offer a tiny taste the first time, then watch your cat for two days for vomiting or diarrhea. If either appears, stop giving potato.
How much?
PetMD's veterinary guide suggests no more than one ½-inch cube of plain cooked potato. If your cat has no stomach upset over the next two days, a small taste once or twice a week is the limit, and all treats together should stay under 10% of your cat's daily calories.
Which mashed potato add-ins are the problem?
Mashed potatoes become unsafe for cats mainly because of what goes into the pot. PetMD's veterinary guide says mashed potato is acceptable for cats only when it is plain, with the skin removed and no butter, gravy or seasoning. Here is why the usual extras matter:
- Garlic, including roasted garlic and garlic powder: an Allium that damages red blood cells, and more toxic than onion
- Onion, chives and scallions: the same plant family as garlic, with the same risk
- Milk, cream and sour cream: dairy, which can cause diarrhea or other digestive upset
- Butter and cheese: rich and fatty, adding calories a cat does not need
- Gravy: fatty and salty, and often made with onion
- Salt: the ASPCA notes that too much salt causes thirst and increased urination, and that salt poisoning can cause vomiting, tremors and seizures
Potato skins, green potatoes and raw potato
Potato skins, green potatoes and raw potato are the parts of a potato that cats should never eat. PetMD's veterinary guide explains that they contain solanine, and that the skin contains it whether raw or cooked. Signs of solanine poisoning range from nausea, vomiting and diarrhea to tremors, seizures and loss of consciousness in severe cases.
PetMD's guide advises contacting a veterinarian right away if a cat eats any raw potato or any amount of potato skin. Store potatoes where your cat cannot reach them, and keep cats away from potato plants in the garden.
My cat ate mashed potatoes. What should I do?
Mashed potatoes that were plain, eaten in a small amount by a healthy cat, are unlikely to cause more than a mild stomach upset. Watch your cat for vomiting or diarrhea, and call your vet if it seems unwell or stops eating.
Mashed potatoes that contained garlic, onion or chives are a different matter. The Merck Veterinary Manual describes cats as the species most susceptible to these plants and notes that the breakdown of red blood cells typically happens three to five days after exposure, so a cat can look fine at first. Call your vet or an animal poison control service even if your cat seems well, and tell them what the dish contained.
Fries, chips and baked potatoes
French fries and potato chips are not good treats for cats. PetMD's veterinary guide says both are too high in fat and salt and offer little nutrition, and fried potato skins still contain solanine.
Baked potato is safe only in part: PetMD's guide says the plain inner flesh, away from the skin, is fine in small amounts, but the skin should never be eaten. Loaded baked potatoes topped with butter, sour cream, cheese, bacon or chives are not suitable for cats.
Common questions
Are mashed potatoes good for cats?
Only in limited ways. Plain cooked potato is not toxic to cats, but it is not good for them either. PetMD's veterinary guide calls potatoes empty calories for cats and points out that cats are poorly suited to digesting carbohydrates.
Are mashed potatoes bad for cats?
It can be. Risks to watch for: garlic, onion, chives or scallions, including garlic mashed potatoes and mash seasoned with garlic or onion powder; butter, milk, cream, cheese and sour cream.
Are cats allowed to have mashed potatoes?
Only in small amounts and the right form. Set aside a small piece of potato before you add butter, milk or seasoning.
Are sweet potatoes safer than potatoes for cats?
Sweet potatoes do not contain solanine, and PetMD's veterinary guide considers them non-toxic to cats. They are still mostly carbohydrate, so the same rules apply: plain, cooked and in small portions.
Can I mix mashed potato into my cat's food every day?
No. PetMD's veterinary guide suggests a small taste once or twice a week at most, and treats should stay under 10% of your cat's daily calories. Potato should never replace a complete and balanced cat food.
Can cats eat garlic mashed potatoes?
No. Garlic is toxic to cats, and the Merck Veterinary Manual rates it three to five times more toxic than onion. If your cat has eaten garlic mashed potatoes, call your vet even if it seems fine, because signs of anemia can take several days to appear.
Sources
- PetMD. Can Cats Eat Potatoes? (Sandra C. Mitchell, DVM, DABVP)
- ASPCA Animal Poison Control Center. People Foods to Avoid Feeding Your Pets.
- Merck Veterinary Manual. Garlic and Onion (Allium spp) Toxicosis in Animals.
- ASPCA Animal Poison Control Center. People Foods to Avoid Feeding Your Pets.
- Cornell Feline Health Center. Feeding Your Cat.
If your cat has eaten something toxic, contact your veterinarian, an emergency animal hospital or an animal poison control service right away, even if your cat seems fine. Do not try to make your cat vomit at home.