Can Changing Dog Food Cause Problems? How to Switch Safely

Yes. A sudden change in dog food can cause diarrhea, vomiting, gas, or a reduced appetite, even when the new food is nutritious. Your dog’s digestive system needs time to adjust to different ingredients and nutrient levels. Check the new food’s label for ingredients your dog has reacted to before, especially if they have a known sensitivity.

Unless your veterinarian advises otherwise, replace the old food over about seven days. Start with 25% new food and 75% old food for two days, move to a half-and-half mix for two days, then use 75% new food for two days before serving only the new food. For a day-by-day plan, see the guide to changing your pet’s food safely.

Check your dog’s stool, appetite, energy, and comfort each day during the switch. Mildly soft stool may improve as the transition continues, but repeated vomiting, watery diarrhea, or refusal to eat calls for a veterinarian’s advice. Keep treats and table scraps consistent so it is easier to tell whether the new food is causing a problem.

Different dog foods can have different calories per cup, so the old serving size may not fit the new formula. Compare the calorie information and feeding directions on both packages, then measure meals rather than estimating. If your dog needs a prescription diet or has a medical condition, ask your veterinarian how quickly to make the change.