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My 20 kg dog ate two full slices of cheese pizza — when might vomiting or other signs start, and how long could they last?

Dogs · Food safety

Last reviewed: 2026-09-05 · Reference ranges: ASPCA, Pet Poison Helpline & Merck Veterinary Manual

Short answer

Gastrointestinal signs like vomiting, diarrhea, or abdominal discomfort often start within 4 to 12 hours after a dog eats pizza. The high fat, salt, and potential onion or garlic powder can irritate the stomach. For a 20 kg dog, two slices is a significant amount, so signs could persist for 24 to 48 hours depending on individual sensitivity. Offer small amounts of water and a bland diet if vomiting subsides, but if signs are severe or last more than a day, a vet visit is wise.

Pizza — Food safety facts

Feed with care · Dogs · full breakdown on the linked food page

The dough, cheese and sauce bring salt, fat and usually onion and garlic powder.

Dogs and cats carry the same rating (Feed with care), so the notes below hold for either pet.

Pizza is not poisonous to dogs, but it is easy to over-feed. Rich fat, salt or seasoning can bring on vomiting or diarrhoea within a day, and repeated large portions are a recognised trigger for pancreatitis.

If it ate some before you noticed, watch for vomiting, diarrhoea, loss of appetite, unusual tiredness or a painful, swollen abdomen over the next 24 hours. A one-off small amount in a healthy adult usually passes with water and rest; repeated exposure, a puppy or kitten, a senior, or a pet with an ongoing illness is a reason to call your vet the same day.

Why these cautions matter

Garlic and onion damage a pet's red blood cells and can bring on anaemia. Signs are often delayed for several days, so looking fine straight afterwards does not rule it out.

A heavy salt load drives up thirst and urination, and in the worst cases leads to sodium ion poisoning, which is a genuine emergency.

Rich, fatty food is the classic trigger for pancreatitis, a painful inflammation of the pancreas that usually needs veterinary treatment rather than rest alone.

Most adult pets make very little lactase, so dairy tends to produce gas, bloating and diarrhoea instead of usable nutrition.

The full verdict, portion guidance and serving notes are collected on the Pizza food facts page.

Open the full food page: Pizza food facts →