The difference between black stools caused by spinach and real black stools is usually the color and accompanying symptoms are different. Black stools caused by spinach do not have abdominal discomfort, the fecal occult blood is negative, and the color of the stools will return to normal after changing the diet. However, black stool caused by gastrointestinal bleeding is positive for fecal occult blood, and the color of stool cannot be restored after changing diet. 1. Eating spinach black stool: black stool is mainly dark black and dark gray, black stool time is mostly 3-4 days, no other symptoms. The reason of eating spinach black stool is mainly related to spinach, spinach itself is a kind of green leafy food, after eating, the feces may become black. Because spinach contains a large amount of iron, this iron ingested into the body, if not fully absorbed, it will lead to black stool, fecal occult blood test is negative, change the diet after the stool is normal. 2. True black stool: the color is tar-like bright black, especially when the amount is large, most patients have a history of disease, such as peptic ulcer, cirrhosis of the liver, etc., and severe cases can be accompanied by palpitations, dizziness or even fainting, pallor and other symptoms. Usually true black stools mean upper gastrointestinal bleeding and a positive fecal occult blood test. If you have black stools and cannot tell the difference between real and fake, you need to consult a doctor and undergo relevant examinations to clarify the cause and standardize the treatment.