Vomiting and Diarrhoea in Cats: Causes and What Tests

Vomiting and diarrhoea are the most common gastrointestinal complaints in cats. Sometimes it is a one-off reaction (a hairball, a food change), and sometimes a sign of poisoning, infection or organ disease. In cats dehydration sets in fast, so it matters to tell the harmless from the dangerous in time. Let's break down the causes, what to do and what tests to run.

Common Causes of Vomiting and Diarrhoea in Cats

• Hairballs (trichobezoars) — a common cause of vomiting.
• Diet errors: a food change, overeating, intolerance.
• Parasites and infections (especially in kittens).
• Foreign body (thread, tinsel — dangerous!).
• Organ disease: GI tract, pancreas, liver, kidneys, hyperthyroidism.
• Toxins (many plants and human medicines are poisonous to cats).

When It Is Dangerous (Red Flags)

See a vet urgently if:

• vomiting with blood or repeated, diarrhoea with blood;
• the cat is lethargic, not drinking, hiding, with abdominal pain;
• it lasts more than a day or there is heavy dehydration (skin tents, dry gums);
• the cat is not eating alongside vomiting/diarrhoea — especially dangerous in cats (risk of hepatic lipidosis);
• a kitten or old cat — seek help sooner.

Vomiting White Foam, After Eating, Hairballs

White foam/bile on an empty stomach happens with an empty stomach; right after eating — overeating or gulping; periodic vomiting of a hairball is common, but if frequent or with diarrhoea, a work-up is needed. Any blood warrants a vet.

What to Do at Home (No Red Flags)

If the cat is active, the episode is a one-off, without blood: withhold food for a few hours, ensure water (dehydration is the main risk), then small portions of a bland diet. Do not give human medicines — many are toxic to cats. No improvement in a day or red flags appear — see a vet.

What Tests to Run

Baseline — a complete blood count and biochemistry (inflammation, liver, kidneys, dehydration) plus a stool test if needed; the blood breakdown is in cat blood test. If a foreign body is suspected — ultrasound for dogs and cats. If the cat refuses food — why a cat is not eating.

To understand your pet's tests in plain language, upload the form (PDF or photo) to the pet results interpretation service. This helps you understand the result but does not replace a vet.

This article is informational. Diagnosis and treatment of your pet are the job of a veterinarian.