Can magnesium citrate cause stools to turn black?

Don't know about magnesium citrate, but found that Bepto-Bismol (the pink stuff) can cause your stool and tongue to turn black. It goes way when you reduce the amount of Beto you are using, if any,

Its normal but it will cause Hard stool and may cause you to bleed but don't worry its not your your stool

No. Iron will do that tho. You probably need a stool test for blood.