How to change dog food without an upset tummy
Updated 7 November 2026. 3 minute read.
Short answer: Switch over 7 to 10 days. Start with about a quarter new food and three quarters old food, move to half and half, then three quarters new, then all new. Go slower for sensitive dogs. A probiotic during the change can help keep stools firm.
The 7 to 10 day plan
Days 1 to 3: about 25% new food, 75% old. Days 4 to 6: half and half. Days 7 to 9: 75% new, 25% old. Day 10 onwards: all new food. If stools soften at any stage, go back a step and stay there for a few extra days.
Why sudden changes cause problems
The bacteria in your dog's gut are adapted to what they normally eat. A sudden switch, especially to a richer or very different food, gives them no time to adjust, and loose stools or wind follow.
Helping a sensitive dog
Stretch the change over two weeks or more. Keep treats simple while you switch. A daily dog probiotic with prebiotic fibre during the change, and for a week afterwards, supports a settled gut.
When to stop and call the vet
If there's vomiting, blood, your dog is off their food, or diarrhoea lasts more than 48 hours. It may be a food intolerance or something unrelated to the change.
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Common questions
Can I switch dog food straight away?
Some dogs cope, but many get an upset tummy. A gradual change over 7 to 10 days is much safer.
Is it normal for a dog to have loose stools when changing food?
Slightly softer stools are common during a change. Slow down the switch. If it's watery, bloody or lasts beyond 48 hours, see your vet.
Should I give a probiotic when changing dog food?
Many owners do, and vets often suggest it for diarrhoea from a sudden food change. It helps support the gut bacteria while they adjust.
This page is general advice, not a diagnosis. If you're worried about your dog, speak to your vet.
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