Diarrhoea after a change of food

two rabbits, a cat and dog on white background


Some pets will struggle to digest a new food unless it’s introduced slowly into their normal diet – so, if your pet eats something they aren’t used to it may give them diarrhoea.

Usually this type of diarrhoea passes with very little treatment but it’s important to make sure your pet gets better quickly and that there’s no other possible cause for their diarrhoea.

Contact your vet immediately if you think your pet has eaten something that may harm them.

Other symptoms

A change of diet can cause a tummy upset. Symptoms include:

  • Diarrhoea
  • Vomiting
  • A painful tummy - you may notice them yelping when they are picked up, growling when you touch their tummy or sitting in a “prayer position” with their front legs on the floor and hind legs stood up
  • Excessive wind (farting)
  • Sleeping more or being quieter than usual
  • Eating less than usual.

When to contact your vet

Diarrhoea due to a sudden change in food usually settles without treatment within 1-3 days. However, if diarrhoea is severe or is left for too long your pet may get dehydrated and become poorly. Contact your vet without delay if your pet has any of the following symptoms:

  • Diarrhoea for more than 2-3 days
  • Intermittent diarrhoea for 2 weeks or more
  • They are very young or very old and have diarrhoea
  • Diarrhoea and other health issues
  • Diarrhoea whilst taking medication (especially anti-inflammatories).

Contact your vet immediately if you think your pet has eaten something that may harm them.

You know your pet best. If they don’t have the symptoms listed above but you are still concerned it’s always best to contact your vet.

How long will it take my pet to recover?

If your pet's diarrhoea is because of a change of diet most will recover within 1-3 days.

Why does my pet develop diarrhoea after a change in food?

Usually, diarrhoea after eating a new food is simply because your pet’s guts haven’t had time to adjust to it.

Our pets typically eat a very similar meal twice daily for most of their lives. Think of yourself eating meat, potatoes and vegetables every day for a few months then out of the blue, eating a spicy curry. It’s likely you would suffer a tummy ache, possibly vomit or have diarrhoea after that!

Other reasons include:

  • Your pet could be allergic to the new food
  • The food may have been under-cooked
  • Your pet may have eaten too much food which has overwhelmed their guts.

Home care for diarrhoea

Diarrhoea is a very common problem in pets, fortunately it often passes within 1-2 days.

If your pet has diarrhoea (without blood or mucus) but is otherwise happy, well and behaving normally you could try to settle them at home. If they don’t improve quickly or you are concerned about them at any point book an appointment with your vet.

Suggestions to settle your pet’s stomach:

A bland diet

An easy-to-digest diet can speed up recovery. Don’t give your pet anything rich or fatty – this could make their diarrhoea much worse! Plain white rice or plain boiled chicken (without skin or bones) can be used in the very short term but bland diets are also available from your vet.

Smaller meals

Feed your pet very small meals throughout the day. This keep their guts moving without overwhelming them.

Plenty of water

Pets who are suffering from diarrhoea might need to drink a bit more than usual to replace the extra water they’re losing in their poo. Make sure your pet has access to plenty of water and that they are drinking throughout the day. Speak to your vet if your pet stops drinking or is drinking much more than usual.


Let your pet rest and recover and avoid anything energetic until they are feeling better. If they are very lethargic then you should speak to your vet.


Probiotics are friendly bacteria for your pet’s gut that can be beneficial for some pets but not all. Probiotics are thought to work by topping up the normal bacteria and binding nasty bacteria and toxins. Probiotics can be found at your vets or online.

Gradually reintroduce their normal food

Your pet should be back to normal after a couple of days. Once they’re passing solid poo you can start to reintroduce their normal diet slowly over a few days.

How to change your pet's food

To prevent diarrhoea, keep your pet’s diet as consistent as possible from day to day. If you need to change their food, do it slowly and see our website advice on changing your dog's food or changing your cat's food

Published: June 2018

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Written by vets and vet nurses

Illustrations by Samantha Elmhurst