That's the problem...I don't believe them, until I have proof otherwise. 50% of the time, there's nothing there. 20% of the time, I might get black stool but it's clearly heme negative. After they recover from the shock of there being zero blood in their stool, and after denying up and down that they took any iron supplements or pepto....they suddenly remember getting up at 3a.m. yesterday to drink some pepto for indigestion. As I'm sure you're already well aware, plenty of things can turn your stool black or red besides blood and virtually all of my patients, at least in my current pt population suffer from some variant of short term memory loss when it comes to food or medicines that they have ingested in the last 5 days.
Red stools = Red food coloring, beets, cranberries, tomato juice, soup, red gelatin, red drink mixes, red peppers and of course....wait for it....Flaming Hot Cheetos
Black stools = iron supplements, bismuth (pep-bismol, maalox, mylanta, rolaids, etc..), licorice, grape juice, oreos, charcoal health drinks, etc..
I mean, what do you do for someone like I described who's swearing that his stools are all turning black and denying any dietary/medicine confounders? Let's say he even demonstrates a mild to moderate anemia. Are you going to admit that guy...just because he swears to you there is blood in his poop and he's got a low HCT? There is nothing more embarrassing than reading a GI note the next day that documents "rectal exam demonstrates black stool that is clearly heme negative. Apparently, no DRE was performed in the ER which would have clearly demonstrated no evidence of melena and upon further inspection of the MAR, the pt apparently is taking iron supplementation for his documented iron deficiency anemia although he was not aware of this fact. Signing off."