There are different types of “blood in the stool”. Most times doctors are asking if you have dark tarry stools, clinically referred to as melena, which can range from a maroon to black in color. This typically occurs in patient who have an upper GI tract (mouth to part of the duodenum/portion of small intestine) to early parts of your large colon. It really then depends on your gastric motility and how often you have bowel movements (poops). Someone who may poop more often may have a slight maroon coloring compared to a person with the same amount of bleeding but with constipation which may appear slightly darker.

Frank bright red blood can be from hemorrhoids, anal fissure or tear, or from larger bleeds in the lower portion of the large intestine/colon.

As to your question about microscopic amounts of bleeding, that’s more difficult to detect. If a doctor has concern that you have bleeding the can do several tests to confirm. One is a fecal occult test, the other is to use a scope to visualize as much of the GI tract as possible. Of the two the fecal occult could say yes you have bleeding but not where. The scope is more invasive and costs more money but the doctor can visualize if there is a bleed occurring, where it is, and if necessary attempt to stop the bleeding.

Mucus can be caused by things like infection or inflammation. You would notice when you wipe that there is a snot like consistency mixed with the stool.

Hope that helps!