Dog diarrhoea (including bloody diarrhoea)
Brief, mild diarrhoea in a bright dog is common and often settles, but bloody or black tarry diarrhoea, profuse watery diarrhoea, or diarrhoea in a dog who is weak, collapsing, vomiting repeatedly or has a painful belly needs urgent veterinary care. Large or bloody fluid losses cause rapid dehydration and can signal haemorrhagic gastroenteritis, parvovirus, poisoning or other serious illness. Puppies and small or elderly dogs decline fastest, so do not wait if any red flag is present.
Go to a vet now if
- Blood in the stool, or black tarry diarrhoea
- Profuse watery diarrhoea, especially with vomiting
- Weakness, collapse, pale gums or a painful, swollen belly
- A young, small or elderly dog, or an unvaccinated puppy
Call a vet today if
- One or two softer stools in a bright, active, well-hydrated dog
- Mild upset after a diet change that is already improving
What to tell the vet
- How long, how often, and how watery
- Any blood or black colour
- Whether your dog is also vomiting
- Possible access to toxins, bones, bins or new foods
- Vaccination status (especially puppies)
- Weight, age and any medications
What not to do
- Do not give human anti-diarrhoea or pain medicines without veterinary advice
- Do not withhold water — dehydration is the main danger; offer small frequent sips
- Do not delay for a bloody-diarrhoea puppy — suspect parvovirus and call now
What your vet may check
Your vet may assess hydration, examine the abdomen, and may run faecal tests, blood work or imaging to find the cause. Treatment can include fluids and anti-nausea medication and is always veterinary-led.
Recovery support after veterinary assessment
After your vet has assessed your dog and addressed the cause, they may recommend a bland diet and a gradual return to normal food. For the recovery phase during and after acute diarrhoea, plant-based digestive support such as Alfavet DiaTab or DiaTab PRO may be suggested on veterinary advice — supportive, not a replacement for assessment.
Frequently asked questions
When is dog diarrhoea an emergency?
Blood or black tarry stool, profuse watery diarrhoea, diarrhoea with vomiting or weakness, and any diarrhoea in an unvaccinated puppy are emergencies. Call a vet rather than waiting.
Is bloody diarrhoea in dogs always serious?
Bloody diarrhoea can signal haemorrhagic gastroenteritis, parvovirus or poisoning and can cause dangerous fluid loss. It warrants a prompt veterinary call, especially in puppies and small dogs.
What can I give a dog with diarrhoea at home?
Keep water available and contact your vet before giving anything. Human medicines can be harmful, and the safest plan depends on the cause your vet identifies.
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Sources & standards
Emergency guidance follows AVMA, Merck Veterinary Manual, ASPCA Animal Poison Control, and small-animal emergency-medicine standards, reviewed by our veterinary advisory board.