How long after taking iron tablets will my stool remain black? i stopped on friday and i have a bm once every 3 or so days and still black :/ nervous. they are formed; but black.

Variable: It depends on the transit time through your gut. If you have a fast transit it could be many hours -- but if you are slow, it could be several days. If you are constipated (once every 3 days is constipated), you are going to have dark stools for perhaps a 7-10 days. Don't worry about it.

Don't worry: If you have a bm only once every 3 days, this means that the iron would stay in the stool until you have the next bm. If the dark color extends beyond 2 bm cycles, then you should get checked out.