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Dog Diarrhoea: Home Treatment and When to See a Vet

Diarrhoea is one of the most common ailments in dogs, and in most cases it resolves on its own within a day or two with simple management at home. However, knowing when diarrhoea requires veterinary attention — rather than watchful waiting — is an essential skill for every dog owner.

Common Causes of Dog Diarrhoea

Acute diarrhoea in dogs most commonly results from dietary indiscretion — eating something that disagrees with the gut, such as scraps, rubbish, or something found on a walk. Other common causes include a sudden change in diet (always transition to new food gradually over 7–10 days), stress, a viral or bacterial gastrointestinal infection, intestinal parasites (particularly Giardia and roundworms), and food intolerance.

Chronic diarrhoea — persisting for more than 3 weeks or recurring regularly — suggests an underlying condition requiring investigation. Common causes include inflammatory bowel disease (IBD), exocrine pancreatic insufficiency (EPI), food allergy, and intestinal tumours in older dogs.

The character of the diarrhoea provides useful information. Large-volume, watery diarrhoea suggests a problem in the small intestine. Frequent, smaller amounts of mucus-containing diarrhoea, often with straining, suggests a large intestinal (colonic) problem. Blood in the stool — either bright red (haematochezia) or dark and tarry (melaena) — requires veterinary assessment.

Safe Home Treatment for Mild Diarrhoea

For a healthy adult dog with mild, uncomplicated diarrhoea and no other symptoms, the following home management approach is widely recommended by UK vets including PDSA-trained practitioners. First, ensure your dog has constant access to fresh water — diarrhoea causes fluid and electrolyte loss, and maintaining hydration is the priority.

Contrary to older advice, most vets no longer recommend prolonged fasting. Instead, feed small, frequent meals of a bland, easily digestible diet: plain boiled chicken and white rice is the classic option, or a commercial gastrointestinal diet from your vet. Offer smaller portions than usual — about half the normal daily amount — and feed in 3–4 smaller meals across the day.

Probiotics specifically formulated for dogs (such as Pro-Kolin or Fortiflora) can help restore gut flora and shorten the duration of diarrhoea. These are available without prescription from vet practices, pet shops, or online. Do not use human probiotics (such as Yakult) — these are not formulated for dogs and may not be helpful.

When to Call the Vet

Call your vet promptly — same day or next day — if your dog's diarrhoea: has not improved after 24–48 hours of home management; is accompanied by vomiting, lethargy, or significant appetite loss; contains blood or dark, tarry material; occurs in a puppy (especially one that is not fully vaccinated — possible parvovirus); occurs in an elderly dog or a dog with a known health condition; or is severe and watery, suggesting significant fluid loss.

Seek emergency veterinary care immediately if your dog is: very lethargic or appears to be in shock; has diarrhoea and vomiting together (rapid dehydration risk, particularly in small dogs and puppies); has dark, tarry stools (melaena — indicates upper GI bleeding); or has known or suspected exposure to a toxin.

Parvovirus in particular can cause rapid deterioration — an unvaccinated puppy with diarrhoea and vomiting must be seen urgently. This highly contagious viral disease carries a significant mortality rate without intensive treatment.

Checking for Parasites

Intestinal parasites — roundworms, hookworms, whipworms, and Giardia — are a common cause of diarrhoea in dogs, and some are zoonotic (transmissible to humans). If your dog has recurring diarrhoea or has not been regularly wormed, a faecal test to check for parasites is a sensible step.

Faecal examination is available at most vet practices for around £20–£40. Some practices offer faecal antigen testing for Giardia specifically, which is the most reliable method of detection for this particular parasite. Treatment typically involves a course of fenbendazole (Panacur) for most worms and either fenbendazole or metronidazole for Giardia.

The PDSA recommends worming adult dogs every 3 months as a routine preventive measure. If you have young children in the household, regular worming is particularly important given the zoonotic risk from Toxocara canis (roundworm) to humans.

Compare Vet Costs for Gastrointestinal Treatment

Treating a dog with diarrhoea can range from almost nothing (home management only) to several hundred pounds if diagnostic tests and prescription medication are needed. A consultation for gastrointestinal symptoms typically costs £40–£65. A faecal test adds £20–£40, and blood tests to assess hydration and organ function add £80–£150.

If your dog is frequently affected by gastrointestinal issues and requires ongoing medication or prescription diets, knowing which local practices offer the most transparent and competitive pricing matters. CompareMyVet at app.comparemyvet.uk helps you compare local vet fees in an honest, straightforward way.

For any prescription medications — such as metronidazole for Giardia or a prescription gastrointestinal diet — remember that under the March 2026 CMA reforms you are entitled to a written prescription, allowing you to purchase from a registered pharmacy of your choice.