Upset after a food change

What this tends to look like

• Began within a few days of a new food, a new treat, or a new batch
• Loose or soft stool more than vomiting
• Appetite often still reasonable
• No blood, no straining, no fever
• Otherwise behaving normally

What is usually going on

The gut bacteria that digest a given diet take days to shift when the diet does. Change food abruptly and the population lags behind, which shows up as soft stool and gas. This is the most predictable and least worrying cause of diarrhea there is, and the fix is usually pace rather than medicine. It matters that a food intolerance looks similar at the start, so if it does not resolve, the food itself is the suspect.

What people commonly use

Educational information only — not veterinary advice. Check with your vet before starting anything new.

Where to find them

Sold by third-party retailers. We may earn a commission at no extra cost to you.

What you can do at home

• Slow the transition down. Go back to roughly a quarter new food to three quarters old, then shift by about a quarter every three days
• Add plain canned pumpkin, not pie filling, which is sweetened and spiced
• Give a probiotic through the transition and for a week after
• Keep everything else constant. Changing food and treats and a supplement at once tells you nothing about which mattered
• Note the exact product and protein source, since if this becomes a pattern that information is the diagnosis

When to stop and call your vet

• Diarrhea continues beyond about three days despite slowing the change
• It returns every time you reach a certain proportion of the new food
• Weight loss, or a coat that is deteriorating
• Blood or mucus in the stool, or straining to pass it