the most serious cause of black stools is bleeding from somewhere in the gi tract. bleeding in the stomach esophagus or intestines can turn into a black color by the time it leaves the body as stool. this can be caused by bleeding ulcers stomach inflammation broken blood vessels in the esophagus called varices or tumors. this type of bleeding can be life-threatening. the bleeding can also come from a nosebleed or from the mouth if blood is swallowed. black stools can also be caused by supplements such as iron or medicines such as pepto-bismol. certain foods like blueberries or black licorice can also turn the stool black. your doctor can tell if there is any blood in the stool by taking a stool sample from the rectum and performing a simple test in the office. if you are having any black or tarry stools call your doctor right away.
what can cause black colored stools?