Why does my dog have diarrhoea? Causes of diarrhoea in dogs

While a one-off bout of diarrhoea may simply be a sign that your dog has eaten something that’s unsettled their stomach, there are many possible causes of diarrhoea in dogs.

Dog diarrhoea is a good reason to visit your local vet, who will help to establish the cause and recommend treatment, if necessary. Prolonged bouts of diarrhoea can quickly cause your dog to become dehydrated, so it’s important to be vigilant.

Diarrhoea in dogs: the warning signs

If your dog has a one-off bout of diarrhoea but is otherwise alert, active, and showing no other symptoms, it’s no cause for alarm unless there is blood in the diarrhoea.

If he’s lethargic, has diarrhoea for over 24 hours, is vomiting, loses his appetite, or displays any other symptoms, don’t delay – get him to your local vet, fast.

Always book an appointment right away if the diarrhoea contains blood, or if you suspect your dog has come into contact with a toxic or harmful substance.

Common causes of dog diarrhoea

There are many possible causes of diarrhoea in dogs – we’ve listed some of the most common reasons below.

• Worms
• Sensitive stomach
• Changes to their diet
• Lactose intolerance
• Stomach infections (gastritis)
• Colitis
• Serious conditions such as inflammatory bowel disease (IBD)
• Ingesting poisonous or harmful substances

Causes of diarrhoea in dogs

An infestation of worms, such as roundworm or tapeworm, can trigger diarrhoea in your dog. When it comes to worms, prevention is better than cure, and a regular worming routine will help to keep your dog worm free.  Keep in mind that not all wormers are as effective as each other.  Your vet will advise the best wormer for your dog and situation.

If your dog has a particularly sensitive stomach he may be unable to tolerate certain foods, which can lead to diarrhoea. Any changes to your dog’s diet can cause stomach upsets, so it’s best to stick to a balanced, healthy diet that your dog is used to – particularly if he has an intolerance to certain foods. Your vet will advise you on a suitably bland diet.

Stomach infections (gastritis) are a common cause of diarrhoea in dogs – and often trigger both sickness and diarrhoea. A bland diet (see above) and plenty of water can help clear up the problem in a few days, but always consult your vet if your dog doesn’t recover quickly.

If the diarrhoea is accompanied by blood and/or mucus, it may be a sign of colitis in your dog. Colitis is an inflammation of the colon in dogs, and is often eased by feeding your dog a bland diet (see above) after 24 hours without food, or a course of anti-inflammatory medication.

While relatively common, colitis can lead to the more serious inflammatory bowel disease (IBD) so it’s always best to get a dog with diarrhoea checked out by your local vet.

A number of serious conditions can cause diarrhoea in dogs, including inflammatory bowel disease, congestive heart failure, diseases of the central nervous system, cancer, liver and kidney diseases.

Your vet will test your dog to rule out these conditions if necessary, and to establish the best course of treatment to get your dog back in tip-top health.

Ingesting poisonous or harmful substances can give your dog sickness and diarrhoea. If you believe your dog has come into contact with a toxic substance, get him to your vet as quickly as possible. Our tips can help you protect your dog from poisonous plants and harmful substances.

Did you know?

After examining your dog, your vet will classify their diarrhoea as either a primary intestinal disease or secondary diarrhoea – the latter meaning the diarrhoea is caused by a more dominant disease.

 “Your vet can advise you on a suitably bland diet for dogs with a sensitive stomach.”

How do I stop my dog getting diarrhoea?

The short answer is, you can’t – but you may be able to reduce the risk of an upset stomach in your dog.
Your vet can give you advice on the best diet to feed a dog with a sensitive stomach, food allergy or lactose intolerance, and it’s vital to keep toxic substances well out of reach of your pooch. See our tips to protect your dog from poisonous plants and harmful substances.

Need help and advice for a dog with diarrhoea?

If your dog has diarrhoea for over 24 hours, make an appointment to see your local vet right away.

Find your nearest vet using our Find a Vet page, or speak to a vet online using Online Vets.