August 13, 2022 · Updated September 26, 2026 · By Collar.pet

Diarrhoea in pets: warning signs and a useful vet-call checklist

In brief

• Watch your pet's energy, appetite and drinking as well as the stool.
• Call a vet promptly for repeated episodes, vomiting, blood or weakness.
• Do not give human medicine unless your vet tells you to.

An isolated loose stool can have many causes, but repeated diarrhoea can lead to dehydration or signal an illness that needs treatment. Puppies, kittens, older pets and animals with existing health problems may become unwell more quickly. A general article cannot tell you whether your pet needs a particular diet, medicine or test. Call your veterinarian for advice if you are worried, and seek urgent help when your pet is weak, repeatedly vomiting, passing significant blood or unable to keep water down.

Observe the whole pet, not only the stool

Note when the problem started and how often your pet needs to go. Is the stool watery, unusually dark or visibly bloody? Has your pet eaten normally, vomited, become less active or had a change in drinking? Mention any new food, treats, medication, travel, possible scavenging or contact with other unwell animals. A photograph or a fresh sample may help if your practice requests one.

The VCA clinical guide to diarrhoea in dogs describes how history, examination and sometimes laboratory tests help establish the cause. The appropriate response varies with the animal's age, general condition and the severity and duration of signs. Do not give human anti-diarrhoeal medicine or antibiotics without a vet's instruction; some products are unsafe for pets or can obscure an important problem.

What to ask when you call

Tell the practice your pet's age, size, medical conditions, the number of episodes and whether vomiting or blood is present. Ask whether an appointment is needed now, what food and water to offer while waiting and what change should trigger an urgent call. For a pet on prescribed medication or a therapeutic diet, check with the vet before altering the routine.

If your veterinarian recommends home monitoring, follow the specific plan and note the time of each episode. Ensure water is available unless the vet directs otherwise, and watch for worsening energy, dry or tacky gums and reduced urination. These observations do not replace an examination; they help you describe the situation accurately.

Prevent the next episode where possible

Once the cause is understood, discuss diet changes, parasite prevention, scavenging and household hygiene with your vet. Avoid repeatedly switching foods after every loose stool; that can make patterns harder to interpret. Keep a record of episodes and any exposure so a recurring problem can be investigated rather than repeatedly guessed at.

General information only; follow your veterinarian's advice for your pet. Substantively updated 26 September 2026.