My question to you is: 
 
I’ve been having some problems with constipation for about 3 years now. However, I’ve been diagnosed with IBS about 2 months ago(irritable bowel syndrome) and I started taking Zelnorm, which helped me greatly. I”m no longer on the medication and the only thing I take right now is Metamucil, and it’s working fine for me. Knowing all that, I”ve been noticing lately that my stool color is darker than what it used to be. Not all the time though. Sometimes it’s just the normal brown color. Other times, it has dark “parts” in it. So it’s not all black, but just has dark spots in it. 
So why do you think that is?? I do take vitamins with iron. ( I heard that iron could cause the dark color) Do you think it’s normal, or is it something to be concerend about??

Dr. Joshua’s Answer:

Iron is known to cause dark colored stool. It’s a good idea to check that there is no “occult” blood in the stool when there is dark color. Home tests are available for that. Talk to your physician about your concern and see if he/she thinks further examinations are necessary.