what does a darker black stool in a dog mean
May 10, 2011. The most common cause of dark stool in dogs is the presence of digested blood in the stool. This is a condition known as Melena and is potentially serious. Although less common, iron toxicity in your dog's system can also result in dark stools. Consult your veterinarian if your dog is passing black, smelly stools on a regular basis.
Black stool in any animal can be a sign of blood in the stool. I would get it checked out by a vet ASAP as it can mean internal bleeding or an ulcer. Black stools (in any animal) are a sign of Iron or blood in the stool. Your dog is bleeding, take them to the vet.