What should I do if my puppy has diarrhea but is still lively?

A puppy with diarrhea but normal spirits and appetite usually points to dietary indiscretion – a puppy’s gut is fragile, and food intolerance, indigestion, overeating, irregular timing or poor-quality food can all cause diarrhea. Check those factors and use proper food and feeding. If diet is fine, try pet probiotics for two days. If diarrhea persists, take it to the vet.