When a dog experiences diarrhea, it is often characterized by loose, watery stools that occur more frequently than usual. This may be accompanied by other symptoms such as vomiting, lethargy, and a lack of appetite. While occasional diarrhea might not be a cause for alarm, persistent diarrhea lasting more than 24 hours warrants veterinary attention. It can lead to dehydration and further health complications, especially in puppies and older dogs.