Why does my dog have runny poo?
Runny or loose poo in a dog is common and usually comes down to something straightforward — a change of food, a scavenged scrap, stress, or a mild stomach bug that settles on its own within a day or two. It is not something to diagnose yourself, but knowing the common causes helps you judge whether to watch and wait or get your dog seen.
The most common causes
A sudden change of food is one of the most frequent triggers, since a dog's digestive system generally needs a gradual transition between diets rather than an overnight swap. Scavenged food — something picked up on a walk, raided from a bin, or an unexpected scrap from a well-meaning visitor — is another very common cause, and often the hardest for an owner to rule out.
Stress and anxiety, from something like a house move, a new pet, fireworks or a change in routine, can also produce loose stools in a dog who is otherwise perfectly healthy. Mild stomach bugs, parasites such as worms, and food intolerances are all common causes too, and several of them can look identical from the outside.
What to look at before deciding what to do
Think about anything that has changed recently — a new food, a treat you do not normally give, a walk somewhere your dog could have scavenged, or a stressful event at home. This is exactly the kind of detail a vet will ask about if you do need to call, so it is worth thinking through even before you decide whether a visit is needed.
Note how your dog is in themselves as well as the stool itself — a dog who is bright, eating normally and otherwise behaving as usual with one or two loose stools is a very different picture from a dog who is also lethargic, off their food, or vomiting.
Red flags that need a vet rather than waiting
Book a vet appointment if the runny poo contains blood or looks black and tarry, if it continues beyond 24 to 48 hours, if your dog is also vomiting, lethargic, or off their food, or if a puppy, senior dog, or a dog with an existing health condition is affected, since these groups can deteriorate faster than a fit, healthy adult.
Do not wait to see if it clears up on its own if any of the above apply, and avoid reaching for a human anti-diarrhoea medication without checking with your vet first, since some are not safe for dogs and treating the symptom does not address whatever is actually causing it.
What generally helps a mild case
For a dog who is otherwise bright and well, many vets suggest a short period of a bland, easily digestible diet — plain cooked chicken and rice is a commonly recommended combination — before gradually reintroducing their normal food over a few days.
Keep fresh water available throughout, since loose stools can lead to some fluid loss, and avoid giving treats or anything new until things have settled. If your dog is not back to normal stools within a couple of days on a bland diet, or seems to be getting worse rather than better, that is the point to call your vet rather than continuing to wait.
Common questions
- Should I withhold food if my dog has runny poo?
- A short period of fasting is sometimes suggested for an adult dog who is otherwise well, but this is not appropriate for puppies, senior dogs, or dogs with existing health conditions, and always check with your vet first rather than withholding food on your own judgement.
- Can stress really cause a dog's poo to go runny?
- Yes, stress and anxiety are a genuinely common cause of loose stools in dogs, often linked to something like a house move, a new pet, fireworks or a change in routine. It usually settles on its own once the stressful event has passed and the dog's routine stabilises.
- How long is it normal for a dog to have runny poo?
- A day or two of loose stools, with your dog otherwise bright and eating normally, is usually nothing to worry about and often resolves on its own. Anything continuing beyond 24 to 48 hours, or accompanied by other symptoms, is worth a call to your vet.
- What foods are gentle on a dog's stomach when they have runny poo?
- Plain cooked chicken and rice, with nothing added, is a commonly suggested bland option for a short period while things settle. Introduce your dog's normal food back gradually afterwards rather than switching back all at once.
- Could worms be causing my dog's runny poo?
- Yes, intestinal parasites are one of several common causes of loose stools in dogs, and it is not something you can reliably confirm just by looking. Regular worming as advised by your vet, and a check-up if loose stools persist, is the way to rule this in or out properly.
Related
Sources
Written against guidance published by UK veterinary and welfare organisations. Always confirm specifics with your own vet.
Written by Matt Garnett, who runs Giddy Pets and is a lifelong pet owner — not a vet. This is general information, not veterinary advice, and it cannot replace an examination by the vet who knows your animal. How we write these guides.