Had black non smelly (abit iron smelly?) stools, not tar like from what i could tell. had this for 2 days now and getting abit worried. taking magnesium and d-vitamin supplements (no iron). should i be worried

?GI Bleeding: Red or black colored stool may be a sign of bleeding in the GI tract (from the esophagus, stomach, small intestine or colon) and should not be ignored. When stool color changes, what tests need to be done depends upon what cause is suspected for the stool color change. For example, gastrointestinal (GI) endoscopy may be required to evaluate red or black stools if bleeding is suspected.