Diarrhoea after a change of food


  • If your pet eats something that they aren’t used to, it may give them diarrhoea unless it’s introduced slowly.
  • This type of diarrhoea usually passes with very little treatment, but it’s important to make sure your pet improves quickly and stays hydrated.
  • It’s important to be sure that there are no other possible causes for your pet’s diarrhoea – contact your vet for advice.
  • Contact your vet immediately if you think your pet has eaten something that could harm them.

Why has my pet developed diarrhoea after a change in food?

Unlike us, our pets tend to eat the same food every day for most of their lives, so a change can be a shock to their guts. Diarrhoea tends to develop simply because your pet’s guts haven’t had time to adjust to the new food.


Diarrhoea and excessive wind (farting) tend to be the most common problems after a sudden change in food. Occasionally, abdominal (tummy) pain and vomiting may occur, but this tends to be short lived.

When to contact your vet

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

  • Diarrhoea for more than a few days
  • Eaten something that may harm them
  • 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)
  • Diarrhoea in rabbits should always be checked by a vet.

How long will it take my pet to recover?

Most pet's suffering from diarrhoea due to a change in food will recover within 1-3 days.

Home care for diarrhoea

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. Diarrhoea in rabbits should always be checked by a vet.

Read our advice on:

How to change your pet's food safely

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:

Published: June 2019

Written by vets and vet nurses. This advice is for UK pets only. Illustrations by Samantha Elmhurst.