How to switch your pet's food without an upset stomach

The 7-day schedule

This is the pattern pet food makers commonly recommend:

• Days 1 and 2: three quarters old food, one quarter new.
• Days 3 and 4: half and half.
• Days 5 and 6: one quarter old food, three quarters new.
• Day 7: all new food.

For a pet with a sensitive stomach, go slower. Purina's guide adds about a tenth more new food each day, reaching all new food somewhere between day 7 and day 10.

Get the amounts right

Foods differ in calories, so a cup of the new food isn't always worth a cup of the old one. Start from the feeding guide on the new food for your pet's weight, or the amount your vet gives you, and mix by those amounts rather than swapping cup for cup.

Cats and new food

Cats can be wary of food they don't know. Keep their mealtimes and eating spot the same while you switch, so the food is the only thing that changes. If your cat won't take to the new food, a different food in the format they already like, wet or dry, may go over better.

Wet to dry, or dry to wet

The same gradual schedule works when you change format. Moving from wet to dry, make sure plenty of fresh water is available. Moving from dry to wet, your pet may drink less water, since wet food contains a lot of it.

What's normal, and when to call the vet

• A little stomach upset in the first few days can happen.
• Call your vet if your pet vomits, has diarrhea or shows any new symptoms during the switch.
• Over the following weeks, watch their stool, weight and coat to see whether the new food suits them.
• If your vet prescribed the new food, follow their instructions for the switch.