The causes of black, unshaped bowel movements may be dietary influences, drug influences, peptic ulcer bleeding and so on. 1. Dietary influences: consuming large amounts of animal blood products, such as duck blood, pig blood, etc., can lead to the appearance of black stools, and if you often consume cold food, greasy food during the diet, it can lead to unshaped stools, and the two situations can be combined, that is, black unshaped stools. 2. Drug effects: such as bismuth and iron preparations of drugs, can lead to black stools, not shaped, usually after stopping the drug can gradually return to normal. 3. Peptic ulcer bleeding: peptic ulcer bleeding can lead to blood mixed into the feces, under the action of the digestive juices black, and one of the common symptoms of peptic ulcer is the stool is not shaped. There may be other reasons for black, unshaped stools, so you can go to the hospital for a checkup to determine the cause.