My dog has diarrhoea but is acting fine: what UK owners should watch

Why a bright dog can still have loose stools

Most short-lived diarrhoea in dogs follows a dietary change: scavenging on a walk, a new food introduced too quickly, table scraps, or a rich treat. The gut reacts, transit speeds up, and stools soften without the dog feeling systemically unwell.

Stress and excitement also matter. Kennelling, travel, house moves and new households commonly produce a day or two of soft stools in dogs that otherwise eat, drink and play normally.

Signs that mean contacting a vet should not wait

Behaviour is a more reliable guide than stool consistency alone. Contact your veterinary practice promptly if any of the following appear, even if your dog seems cheerful between episodes.

• Puppies, elderly dogs, or dogs with existing health conditions and diarrhoea of any duration.
• Repeated vomiting, or an inability to keep water down.
• Fresh blood, dark tarry stools, or straining that produces very little.
• Signs of dehydration: tacky gums, sunken eyes, or skin that is slow to spring back.
• Diarrhoea persisting beyond about 48 hours, or worsening rather than settling.
• Any suspicion your dog has eaten a toxin, a foreign object, or medication not prescribed to them.

Sensible home monitoring for a mild upset

For an otherwise well adult dog, the goal is to keep hydration up, keep food simple, and record what is happening so a vet has useful information if the picture changes.

Do not withhold water. Prolonged fasting is no longer routinely recommended for adult dogs, and it is not appropriate for puppies at all: ask your practice what is right for your dog before withholding food.

• Offer fresh water constantly and note whether drinking is normal, increased or reduced.
• Feed small, frequent, plain meals of the kind your vet recommends for your dog.
• Log the number of stools each day, plus colour, consistency and any blood or mucus.
• Reintroduce the usual diet gradually once stools begin to firm up.

Medicines, wormers and why the class matters

Not every case of diarrhoea is dietary. Parasites, including worms and protozoa such as Giardia, are a recognised cause, and treating them correctly depends on a diagnosis rather than a guess.

In the UK, veterinary medicines are legally classified, and the class governs how they may be supplied. Prescription-only medicines (POM-V) require a valid veterinary prescription, and some parasite products fall under POM-VPS or NFA-VPS supply rules. Never give a dog a human anti-diarrhoeal or a medicine prescribed for another animal.

What to have ready when you call the practice

A short, factual summary shortens the conversation and helps triage. Note when the diarrhoea started, how many episodes there have been, whether your dog is eating and drinking, any vomiting, recent diet changes or scavenging, current parasite treatment dates, and any ongoing medication.

This guide is general information for UK pet owners and does not replace advice from your own veterinary surgeon, who knows your dog's history.