Black dog poop generally is not normal. Dog stool can come in a variety of colors, but most of the times it’s a shade of brown. Black stool that appears dark and tarry usually indicates the presence of digested blood. Blood would be digested if it comes from the upper part of the digestive tract passing down through the small intestines. This means the source of the blood could anywhere from the mouth, esophagus, stomach or small intestines. Conditions or issues such as dental disease, stomach ulcers, toxins, certain medications, infections, kidney disease, liver disorders, bleeding disorders, immune conditions or issues in the gastrointestinal tract itself can be a cause. Occasionally black dog poop may be seen with ingestion of certain non-toxic items or medications. For example, eating blueberries can cause poop to have a black appearance. Certain medications, as they are metabolized, may also cause poop to appear black.