Switching Food
How to switch your dog's food without upsetting their stomach
Most upset stomachs after a food change come down to speed, not the food. Here is the schedule our vets recommend, what is normal along the way, and when to stop.
Why the gut needs time
A new food means a new protein, a new fat level and a new fibre profile. The bacteria in your dog's gut are set up for the old food, and they take a few days to adjust. Move too fast and the result is soft stool, wind or diarrhoea, which then gets blamed on the food. Move at the right pace and most dogs switch without you noticing.
The standard switch: four days in quarters
Mix the two foods in the same bowl rather than feeding them at separate meals, and keep the total daily amount the same as before. A switch is not the moment to change portion size as well.
The slow switch: ten days in tenths
a day, over ten days, for sensitive stomachs, dogs who have reacted to a change before, and every puppy. A puppy's digestive system is not fully mature until three to four months old.
What to expect
- A slightly softer stool for a few days
- A bit more wind than usual
- One extra trip outside
None of these mean the food is wrong. They mean the gut is adjusting.
- Watery stool, or blood
- Vomiting or a bloated belly
- Quiet, off their food, not themselves
These need a vet, not a slower schedule.
If it goes wrong
Go back to the last mix that was fine and hold there for two or three days, then carry on more slowly.
No treats, chews or scraps until the stool is firm. They make it impossible to tell what is causing what.
Stools settle in days. Skin, coat, ears and energy take weeks. If you are switching because of itching, ear trouble or a sensitive stomach, give it six to eight weeks and keep everything else the same.
Moving between wet and dry? Expect the stool to change size. Wet food is up to 80% water, so the dog drinks less and produces a smaller stool relative to what is eaten. Dry food is about 10% moisture, so the dog drinks more from the bowl and the stool looks larger. Both are normal.
- your dog is a puppy or a senior and has diarrhoea for more than a day
- the stool is black or tarry, or there is a lot of blood
- there is vomiting, bloating, or your dog is not themselves
- diarrhoea lasts more than 48 hours, or keeps coming back
Switching a dog with a sensitive stomach? Send us the name of the current food and we will compare the two recipes before you start.
Based on guidance from Cornelia Günther, veterinarian, Happy Dog veterinary team. Reviewed for Happy Dog UK, September 2026.
