My daughter 15 is on ferrous sulfate (200mg 3x daily) for anemia since december. she said after an hour of taking her tablet she got diarrhea. is this normal with this medication?

I consider it likely to be a coincidence in the description posted. If you meant to say diarrhea occurred every time she took a tablet for months it would be a different issue & need an evaluation.

Oral iron more often causes constipation, not diarrhea. It is likely that diarrhea has a different cause. Iron can cause stomach irritation and should be taken with food.

Diarrhea is an uncommon side effect of ferrous sulfate but it can happen, especially your daughter has persistently had this symptom after taking this iron supplement. She can try ferrous fumarate which is better tolerated than the commonly used ferrous sulfate but a little more expensive. If your local pharmacy does not carry this formula, you can buy it on line.