can blueberries make your stool black
Bloody or tarry stools Back to TopConsiderations. Heavy or rapid bleeding in the upper GI tract can cause bright red stools. Eating black licorice, lead, iron pills, bismuth medicines like Pepto-Bismol, or blueberries can also cause black stools. Beets and tomatoes can sometimes make stools appear reddish. In these cases, your doctor can test the stool with a chemical to rule out the presence of blood.