hi there, iron tablets do cause the stool to turn dark coloured or black at times but it could also be due to passage of blood in the gastrointestinal tract. Besides iron tablets do cause gastritis
which can lead to occult bleeding in the stool. According to me
1.stop the iron tablets for the time being if you are not very anaemic
2.get your stool tested for occult blood and for ova and cysts
3.take a course of antacid
or Pantop twice daily for 15 days
4.have regular small meals preferable low in fat and spices.
According to your stool reports and this therapy if there is any relief you can get treated for any infection and change to iron tablets which are less gastroirritant. You should also try to consume iron rich food like dates, jaggery, green leafy vegetables and some portion of red meat to replenish your supply of iron thro' diet. Hope this helps, take care